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Course:EOSC311/2026/Volcanic Ash Composition and its effects on Human Health and Microbial Ecosystems

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== Introduction ==
Volcanic eruptions are mighty natural forces that are able to cause vast changes in ecosystems and the atmosphere. Volcanoes, when they erupt, release large amounts of volcanic ash, volcanic gases, and fragments of rocks that are able to be spread over long distances through many mediums like wind and water, affecting not only local but also global scales. Most of the time, volcanoes are discussed from a geological perspective, but their impacts extend beyond simple things like land formation. Volcanic emissions can affect air, water, and soil quality, impacting both human health and the microbial ecosystem. This project examines the connections among volcanic geology, human health, and microbiology by exploring how volcanic ash affects the respiratory and immune systems, as well as microbial ecosystems.

==Volcanic Ash Composition==

=== 2.1 Formation of Volcanic Ash ===
[[File:VolcanoImage.jpg|thumb|The process by which volcanic ash forms, starting from magma ascending from the mantle to the surface of the Earth. Source: U.S. Geological Survey (Public Domain).]]
Magma is molten rock found beneath the Earth's surface that contains dissolved gases, including water vapor, carbon dioxide (CO₂), and sulfur dioxide (SO₂). As magma rises toward the surface, pressure decreases, causing these gases to escape and form bubbles known as vesicles, similar to how a carbonated drink fizzes when opened. When magma rises quickly, pressure builds up inside these bubbles until they burst, which breaks the magma into fine particles known as volcanic ash (Durant et al., 2010). The composition of the magma affects how explosive the eruption is; magmas with high silica content tend to erupt more explosively and produce greater quantities of volcanic ash.

=== 2.2 Particle Size and Structure ===
During a volcanic eruption, rocks, mineral fragments, and ash are ejected into the air; these are known as pyroclasts. [[File:Respirable Material Content in Volcanic Ash from Major Eruptions.jpg|thumb|400px|Table 1. Respirable material (<4 μm) content in ash from nine historical eruptions. Adapted from Horwell & Baxter (2006).]] Volcanic ash is defined as pyroclasts with a diameter of 2mm or less. This is an important factor in determining how hazardous the ash is to human health. The size is measured using aerodynamic diameter, and particles are classified into two health-relevant categories: thoracic particles (PM10), which are less than 10 μm in diameter, and respirable particles (PM4), which are less than 4 μm in diameter (Horwell & Baxter, 2006). The percentage of respirable material in ash varies considerably depending on the volcano, the explosivity of the eruption, and the distance from the vent at which ash is collected (Horwell & Baxter, 2006).
[[File:VolcanicAsh.jpg|thumb|The shape and size of volcanic ash under a microscope with a 50 micrometer scale bar. Source: U.S. Geological Survey (Public Domain).]]
As shown in Table 1, the proportion of respirable material varies across eruptions. There is no clear relationship to the Volcanic Explosivity Index (VEI). For example, Pinatubo's 1991 eruption had the highest VEI of the group (6) but a comparatively low respirable fraction (9.8%), while Mount St. Helens and Vesuvius, both with a VEI of 5, produced different proportions (11.7% and 16.9%, respectively). This suggests that the explosivity of an eruption alone does not determine how hazardous its ash will be to human health; other factors, such as magma composition and fragmentation style, likely play a larger role in generating fine, respirable particles.

Fine ash particles tend to fall in loose clusters of less than 100 μm, which break apart easily when they hit the ground or are disturbed by external factors, such as wind, passing vehicles, or everyday human activity (Horwell & Baxter, 2006). This means that ash that has already settled on the ground can be lifted back into the air and inhaled all over again, creating an ongoing cycle of exposure even after an eruption has ended. The irregular shape of these particles also makes them more physically damaging once inhaled, as their sharp edges can irritate and damage the airways (Horwell & Baxter, 2006). Together, these structural properties, combined with the small size of respirable particles, make volcanic ash particularly harmful to the respiratory system.

=== 2.3 Chemical and Mineral Composition ===
Volcanic ash is not a single, uniform material; its chemical and mineral composition varies with the type of magma that erupted and the nature of the eruption. Ash is made up of three main components: glass, which is a quenched (rapidly cooled) melt; lithic fragments, which are pieces of pre-existing rock from the volcanic vent; and crystals, which are minerals that formed within the magma before the eruption (Durant et al., 2010). The crystal component can include minerals such as quartz, feldspar, pyroxenes, amphiboles, and olivine, with the exact proportions depending on the magma composition.

One of the most important and dangerous components of volcanic ash is crystalline silica, which can appear as quartz, cristobalite, or tridymite (Horwell & Baxter, 2006). Cristobalite is considered the most toxic of these forms and is particularly common in volcanoes. It forms through a process called devitrification, the conversion of volcanic glass into crystalline material (Horwell & Baxter, 2006).

Aside from crystalline silica, volcanic ash also carries a range of trace elements and chemical species on its surface (Durant et al., 2010). During an eruption, gases such as fluorine, sulfur dioxide, and hydrogen chloride interact with ash particles, leaving chemical coatings on their surfaces (Durant et al., 2010). These surface chemicals can be rapidly released when ash comes into contact with water, contaminating water supplies and soil environments. The presence of iron on ash surfaces is also significant, as it can generate harmful free radicals when it interacts with the lung, potentially causing cell damage even in ash that contains little to no crystalline silica (Horwell & Baxter, 2006).

== Notable Volcanic Eruptions ==

=== 3.1 Mount St. Helens ===
[[File:Vhp img571.jpg|thumb|Mout St. Helens eruption on May 18, 1980, showing the volcanic ash plume produced during the eruption. Source: U.S. Geological Survey (Public Domain).]]
The eruption of Mount St. Helens in Washington, USA, on May 19, 1980, is considered one of the most significant volcanic eruptions in modern history. Following a magnitude 5.1 earthquake, the volcano experienced a lateral blast that destroyed large areas surrounding the mountain. The eruption produced approximately 540 million tons of volcanic ash, which spread across much of the United States and even circled the globe within weeks. The eruption produced a large ash cloud that disrupted transportation, caused environmental damage, and raised respiratory health concerns (U.S. Geological Survey [USGS], 2023). The event demonstrated how volcanic ash can affect areas far beyond the immediate vicinity of a volcano and remains an important case study for volcanic hazard research.

=== 3.2 Comparison of Major Ash-Producing Eruption ===
Several volcanic eruptions have produced significant amounts of ash, including Mount St. Helens (1980), Mount Pinatubo (1991), and Eyjafjallajökull (2010). While Mount St. Helens caused major regional impacts, Mount Pinatubo had global climate effects due to the large volume of ash and gas released into the atmosphere. In contrast, Eyjafjallajökull primarily disrupted air travel across Europe. These eruptions highlight the diverse environmental health and economic impacts that volcanic ash can produce (Newhall & Punongbayan, 1997).

== Effects on Human Health ==

=== 4.1 Respiratory Effects ===
[[File:LungDiagram.jpg|thumb|The human respiratory system, specifically the Alveoli. Source: Canadian Lung Association]]
The respiratory system is a direct target of volcanic ash due to how easily these tiny particles can be inhaled and their sheer abundance during eruptions. Respirable particles are of greatest concern. These respirable particles, due to their size of around 1/20th the width of a human hair, can remain suspended in the air for a long time (Shezi et al., 2020). Because of this size, they can penetrate deeply into the alveolar region of the lungs, where they have the greatest toxic potential (Horwell & Baxter, 2006).

Once these particles reach the alveolar regions, they interact with immune system cells. Resident macrophages and mast cells act as the first line of defense, the primary response, to the inhaled particles. These immune cells are working hard to engulf these particles, a process called phagocytosis. The issue is that, when volcanoes release volcanic ash, it does not release only a few particles. The large quantities of ash in the air after an eruption, along with the number of particles inhaled at once, make it difficult for macrophages and mast cells to remove all of them. As a result, cytokines are released to recruit other immune cells to initiate the second line of defense, but this triggers inflammation. This inflammatory response leads to unwanted effects, such as lung swelling or irritation, which cause coughing or shortness of breath (Horwell & Baxter, 2006).

In addition to these respirable particles, exposure to crystalline silica has been studied in occupational medicine and has been shown to cause silicosis, a serious fibrotic lung disease; prolonged exposure may also increase the risk of lung cancer (Horwell & Baxter, 2006). This makes the crystalline silica content of ash one of the most critical factors in assessing its health hazard. Repeated exposure to these particles, as seen in the Mount St. Helen's eruption, can cause chronic respiratory damage.

=== 4.2 Eye and Skin Irritation ===
Volcanic ash can also affect the eyes and skin. Volcanic ash frequently contains sharp objects that are able to scratch sensitive surfaces when they come into contact. The eyes being exposed to these volcanic ash particles is said to cause unfavourable symptoms like corneal abrasions or scratches, which can cause severe eye pain, conjunctivitis, and more. The skin is also another surface that volcanic ash can attack. When ash comes into contact with the skin, it can cause irritation and reddening of the skin (U.S. Geological Survey).

=== 4.3 Immune Systems ===
The impacts of volcanic ash exposure are noticeable at the respiratory, eye, and skin levels. But the impacts of volcanic ash can extend beyond and are shown to damage the immune system as a whole. As mentioned before, the primary and secondary responses are the body's ways of fighting off bacteria that manage to enter, preventing infections. What is interesting is that volcanic ash has been shown to interfere with these systems (Monick et al., 2013).

Macrophages, the first line of defense, play a role in engulfing foreign particles in a process named phagocytosis. Research shows that volcanic ash can impair macrophages' ability to perform their task, resulting in reduced removal of these foreign particles (Monick et al., 2013). This reduced ability allows more particles to enter the body, increasing the risk of infection and other adverse effects.

Because volcanic ash contains a range of trace elements, such as iron, it can serve as a nutrient source for bacteria to grow and survive within the body (Monick et al., 2013).

== Effects on Microbial Ecosystem ==

=== 5.1 Soil Microbial Communities ===
[[File:Soilrecovery.jpg|thumb|363x363px|The process by which volcanic ash impacts soil environments over time. Source: (Fiantis et al., 2019).]]
Volcanic ash can significantly affect soil microbial communities by altering soil chemistry, pH, moisture retention, and nutrient availability. Immediately after an eruption, a thick layer of ash may reduce microbial activity by covering existing soil and limiting access to oxygen and different organic matter. As a result, the abundance and diversity of microorganisms often decrease in the short term (Fiantis et al., 2019).

However, volcanic ash also contains minerals such as iron, magnesium, potassium, and phosphorus that can gradually improve soil fertility. As weathering occurs, these nutrients are released into the soil and become available to microorganisms. Certain bacteria and fungi can colonize newly formed volcanic deposits and play important roles in breaking down minerals, cycling nutrients, and supporting soil development. Over time, microbial communities help create conditions that allow plants and other organisms to establish themselves, contributing to ecosystem recovery (Fiantis et al., 2019).

Volcanic ash can have both positive and negative impacts on soil microbial ecosystems, depending on whether the effects are considered in the short term or the long term.

=== 5.2 Water Contamination ===
Volcanic ash can enter rivers, lakes, and groundwater through rainfall. Ash particles may increase water turbidity and alter water chemistry, affecting microorganisms that live in aquatic environments. Also, high concentrations of ash can reduce light penetration and disrupt microbial processes that are important for maintaining water quality and ecosystem health (Stewart et al, 2006).

Furthermore, volcanic ash may change the chemical composition of water by releasing minerals and other substances. These changes can alter the balance of microbial communities, causing some species to decline while others become more abundant. As a result, normal nutrient cycling and other ecological processes carried out by microorganisms may be disrupted until the ecosystem gradually recovers (Stewart et al., 2006).

=== 5.3 Recovery and Adaptation ===
Although volcanic eruptions can initially disrupt microbial ecosystems, many microorganisms are capable of adapting to the new environmental conditions. Over time, microbial communities recolonize ash- covered areas and contribute to soil formation and nutrient cycling. This recovery process helps establish conditions that support plant growth and the gradual restoration of affected ecosystems (Fiantis et al., 2019).

== Interconnections Between Human Health and Microbial Ecosystem ==
[[File:Volcanic_ash_infographic.jpg|thumb|516x516px|Volcanic ash and its connections infographic. Source: (OpenAI, 2026)]]
When volcanic ash is deposited in soil and water environments, it does not form an inert layer. Instead, it restructures the chemical and biological conditions of the microbial communities in that area. Ash alters soil carbon and nitrogen concentrations, changes pH, and introduces new minerals and trace elements, thereby affecting which microorganisms survive and thrive (Maltz et al., 2024). Various studies were conducted following the 1980 eruption of Mount St. Helens. These studies showed that microbial communities remained fundamentally restructured for decades, with bacterial and fungal composition varying significantly with ashfall intensity and soil chemistry (Maltz et al., 2024). Along with these studies, research on volcanic ash fertilization was also being conducted. These studies showed that once ash concentrations pass a certain threshold, the soil microbiome shifts. Some bacteria that may help plants grow actually increase, while others decline. This suggests ash doesn't just kill off microbial life, it reorganizes it in complex ways (Staudigel et al., 2025). These shifts matter because soil microorganisms are responsible for nearly all biogeochemical transformations, including nutrient cycling, soil formation, and organic matter decomposition, meaning that disruptions to microbial communities have cascading effects on the broader ecosystem (Staudigel et al., 2025).

These environmental changes caused by ashfall do not remain confined to the soil. They also extend into water systems, such as rivers, lakes, and reservoirs, and ultimately reach human homes and human systems. When ash falls into water supplies, it increases acidity and releases soluble contaminants, including fluoride, iron, sulfate, and chloride, into drinking water (Stewart et al., 2006). It also increases turbidity, which is dangerous because the ash particles present interfere with the disinfection process, allowing harmful bacteria to survive in the water (Stewart et al., 2006). This raises the risk of waterborne disease outbreaks (Stewart et al., 2006). Aside from water contamination, the restructuring of soil microbial communities also affects food systems. Changes in soil chemistry disrupt nutrient cycling, reducing soil fertility and lowering crop yields. In addition, volcanic air pollution has been linked to respiratory illness, cardiovascular effects, and increased healthcare visits among exposed populations (Stewart et al., 2022). This shows that the path from environmental disruption to human health outcomes operates through multiple pathways simultaneously, not just one (Stewart et al., 2022). Together, these interconnections show that the health impacts of volcanic ash cannot be understood by examining geology, microbiology, or human health alone; they are fundamentally linked.

== Conclusion ==
Understanding volcanic ash requires an interdisciplinary approach that integrates geology, microbiology, and statistics to fully evaluate its impacts on ecosystems and human health. This project demonstrates that volcanic eruptions are not isolated geological events; instead, their effects extend across atmospheric, terrestrial, and biological systems, influencing environments and communities long after an eruption.

The hazards associated with volcanic ash are determined by its physical and chemical characteristics, including particle size, mineral composition, and crystalline silica content. These properties influence the severity of respiratory and immune responses in exposed populations. However, the impacts of volcanic ash extend beyond direct human exposure. Once deposited in soil and water environments, ash alters chemical conditions, reshapes microbial communities, and affects nutrient cycling processes essential for ecosystem recovery. These changes demonstrate the interconnectedness of geological processes, microbial systems, and human well-being.

Understanding these complex interactions requires collaboration between multiple disciplines. Statistical approaches allow scientists to analyze relationships between ash properties, exposure levels, and health outcomes to predict risks, while microbiological research shows how ash alters microbial communities, nutrient cycling, and ecosystem recovery. Together, these approaches help develop strategies to reduce the impacts of future volcanic eruptions.

Ultimately, volcanic ash highlights the importance of collaboration across scientific disciplines. Geological knowledge helps explain how ash forms and spreads, microbiological research reveals how ecosystems respond and recover, and statistical methods allow researchers to measure risks and identify patterns. Together, these perspectives provide a more complete understanding of volcanic hazards and contribute to efforts in environmental protection, public health, and disaster preparedness.

==References==
<references />
Baxter, P. J., Ing, R., Falk, H., & Plikaytis, B. (1983). Mount St. Helens eruptions: The acute respiratory effects of volcanic ash in a North American community. Archives of Environmental Health, 38(3), 138–143. https://doi.org/10.1080/00039896.1983.10543892

Canadian Lung Association. ''Your lungs'' [Image]. Canadian Lung Association. <nowiki>https://www.lung.ca/how-to-protect-your-lungs/your-lungs/</nowiki>

Durant, A. J., Bonadonna, C., & Horwell, C. J. (2010). Atmospheric and Environmental Impacts of Volcanic Particulates. Elements, 6(4), 235–240. https://doi.org/10.2113/gselements.6.4.235

Fiantis, D., Ginting, F. I., Gusnidar, Nelson, M., & Minasny, B. (2019). ''Volcanic ash, insecurity for the people but securing fertile soil for the future''. ''Sustainability, 11''(11), 3072. <nowiki>https://doi.org/10.3390/su11113072</nowiki>

Fiantis, D., Ginting, F. I., Gusnidar, G., Nelson, M., & Van Ranst, E. (2019). ''Volcanic ash, soil formation, and ecosystem development.''

Horwell, C. J., & Baxter, P. J. (2006). The respiratory health hazards of volcanic ash: a review for volcanic risk mitigation. Bulletin of Volcanology, 69(1), 1–24. https://doi.org/10.1007/s00445-006-0052-y

Maltz, M.R., Allen, M.F., Phillips, M.L., Hernandez, R.R., Shulman, H.B., Freund, L., Andrews, L.V., Botthoff, J.K., and Aronson, E.L. (2024). Microbial community structure in recovering forests of Mount St. Helens. Frontiers in Microbiomes, 3, 1399416. https://doi.org/10.3389/frmbi.2024.1399416

Monick, M. M., Baltrusaitis, J., Powers, L. S., Borcherding, J. A., Caraballo, J. C., Mudunkotuwa, I., Peate, D. W., Walters, K., Thompson, J. M., Grassian, V. H., Gudmundsson, G., & Comellas, A. P. (2013). Effects of Eyjafjallajökull Volcanic Ash on Innate Immune System Responses and Bacterial Growth in Vitro. ''Environmental Health Perspectives'', ''121''(6), 691–698. https://doi.org/10.1289/ehp.1206004.

Newhall, C. G., & Punongbayan, R. S. (1997). ''The cataclysmic 1991 eruption of Mount Pinatubo, Philippines''. U.S. Geological Survey Fact Sheet 113-97.

OpenAI. (2026). ''Connections with volcanic ash'' [AI-generated image]. ChatGPT. <nowiki>https://chatgpt.com‌</nowiki>{{Projectbox_EOSC311}}
[[Category:EOSC311]]

Shezi, B., Mathee, A., Cele, N., Ndabandaba, S., & Street, R. A. (2020). Occupational Exposure to Fine Particulate Matter (PM4 and PM2.5) during Hand-Made Cookware Operation: Personal, Indoor and Outdoor Levels. International journal of environmental research and public health, 17(20), 7522. <nowiki>https://doi.org/10.3390/ijerph17207522</nowiki>

Staudigel, H., et al. (2025). Tripled plant productivity and soil microbiome restructuring in a greenhouse volcanic ash fertilization experiment. Ecosphere, 16(9), e70406. https://doi.org/10.1002/ecs2.70406

Stewart, C., Johnston, D. M., Leonard, G. S., Horwell, C. J., Thordarson, T., & Cronin, S. J. (2006). ''Contamination of water supplies by volcanic ashfall: A literature review and simple impact modeling.''

Stewart, C., Damby, D.E., Horwell, C.J. et al. Volcanic air pollution and human health: recent advances and future directions. Bull Volcanol 84, 11 (2022). https://doi.org/10.1007/s00445-021-01513-9

U.S. Geological Survey. (n.d.). ''Volcanic ash impacts & mitigation: Eyes and skin''. U.S. Department of the Interior. <nowiki>https://volcanoes.usgs.gov/volcanic_ash/eye_skin.html</nowiki>

U.S. Geological Survey. (2023). ''1980 Cataclysmic Eruption''. Retrieved from <nowiki>https://www.usgs.gov/volcanoes/mount-st.-helens/science/1980-cataclysmic-eruption</nowiki>

U.S. Geological Survey. (2017, December 13). ''Illustration of the basic process of magma formation, movement to the surface, and eruption through a volcanic vent'' [Illustration]. <nowiki>https://www.usgs.gov/media/images/illustration-basic-process-magma-formation-movement-s</nowiki>

U.S. Geological Survey. (2015, November 13). ''Scanning electron microscope image of volcanic ash'' [Photograph]. <nowiki>https://www.usgs.gov/media/images/scanning-electron-microscope-image-volcanic-ash</nowiki>

== Group Contributions and AI Use ==

'''Group Contributions:'''
* Nyamat: Section 2 (Volcanic Ash Composition), Section 6 (Interconnections), and Conclusion
* Raj: Introduction and Section 4 (Effects on Human Health)
* Eric: Section 3 (Notable Volcanic Eruptions) and Section 5 (Effects on Microbial Ecosystems)

'''AI Use Statement:'''
Used Grammarly to revise grammar and spelling throughout the article. Used OpenAI to generate templates for diagrams.

Course:EOSC311/2026/Volcanic Ash Composition and its effects on Human Health and Microbial Ecosystems

2026-06-18T04:11:02Z

RAJMEHRA: change

== Introduction ==
Volcanic eruptions are mighty natural forces that are able to cause vast changes in ecosystems and the atmosphere. Volcanoes, when they erupt, release large amounts of volcanic ash, volcanic gases, and fragments of rocks that are able to be spread over long distances through many mediums like wind and water, affecting not only local but also global scales. Most of the time, volcanoes are talked about from a geological perspective, but the impacts of volcanoes go beyond simple things like land creation. Volcanic emissions can have an influence on air, water, and soil quality that can have an impact on both human health and the microbial ecosystem. This project looks at the connections between volcanic geology, human health and microbiology by exploring how volcanic ash materials have an impact on respiratory and immune systems, as well as microbial ecosystems.

==Volcanic Ash Composition==

=== 2.1 Formation of Volcanic Ash ===
[[File:VolcanoImage.jpg|thumb|The process by which volcanic ash forms, starting from magma ascending from the mantle to the surface of the Earth. Source: U.S. Geological Survey (Public Domain).]]
Magma is molten rock found beneath the Earth's surface that contains dissolved gases, including water vapor, carbon dioxide (CO₂), and sulfur dioxide (SO₂). As magma rises toward the surface, pressure decreases, causing these gases to escape and form bubbles known as vesicles, similar to how a carbonated drink fizzes when opened. When magma rises quickly, pressure builds up inside these bubbles until they burst, breaking the magma into fine particles known as volcanic ash (Durant et al., 2010). The composition of the magma affects how explosive the eruption is — magmas with high silica content tend to erupt more explosively, producing larger amounts of ash.
=== 2.2 Particle Size and Structure ===
During an explosive volcanic eruption, rocks, mineral fragments, and/or ash are ejected into the air; these are known as pyroclasts. [[File:Respirable Material Content in Volcanic Ash from Major Eruptions.jpg|thumb|400px|Table 1. Respirable material (<4 μm) content in ash from nine historical eruptions. Adapted from Horwell & Baxter (2006).]] Volcanic ash is defined as pyroclasts with a diameter of 2mm or less, an important factor in determining how hazardous the ash is to human health. The size is measured using aerodynamic diameter, and particles are classified into two key health-relevant categories: thoracic particles (PM10), which are less than 10 μm in diameter, and respirable particles (PM4), which are less than 4 μm in diameter (Horwell & Baxter, 2006). The percentage of respirable material in ash varies considerably depending on the volcano, the explosivity of the eruption, and the distance from the vent at which ash is collected (Horwell & Baxter, 2006).
[[File:VolcanicAsh.jpg|thumb|The shape and size of volcanic ash under a microscope with a 50 micrometre scale bar. Source: U.S. Geological Survey (Public Domain).]]
As shown in Table 1, the proportion of respirable material varies across eruptions, with no clear relationship to the Volcanic Explosivity Index (VEI). For example, Pinatubo's 1991 eruption had the highest VEI of the group (6) but a comparatively low respirable fraction (9.8%), while Mount St. Helens and Vesuvius, both with a VEI of 5, produced different proportions (11.7% and 16.9%, respectively). This suggests that the explosivity of an eruption alone does not determine how hazardous its ash will be to human health; other factors, such as magma composition and fragmentation style, likely play a larger role in generating fine, respirable particles.

Fine ash particles tend to fall in loose clusters of less than 100 μm, which break apart easily when they hit the ground or when they get disturbed by external factors, such as wind, passing vehicles, or everyday human activity (Horwell & Baxter, 2006). This means that ash that has already settled on the ground can be lifted back into the air and inhaled all over again, making exposure an ongoing cycle even after an eruption has ended. The irregular shape of these particles also makes them more physically damaging once inhaled, as their sharp edges can irritate and damage the lining of the airways (Horwell & Baxter, 2006). Together, these structural properties, combined with how small respirable particles are, make volcanic ash particularly harmful to the respiratory system.

=== 2.3 Chemical and Mineral Composition ===
Volcanic ash is not made up from a single uniform material; its chemical and mineral composition varies depending on the type of magma that erupted and the nature of the eruption. Ash is made up of three main components: glass, which is a quenched (rapidly cooled) melt; lithic fragments, which are pieces of pre-existing rock from the volcanic vent; and crystals, which are minerals that formed within the magma before the eruption (Durant et al., 2010). The crystal component can include minerals such as quartz, feldspar, pyroxenes, amphiboles, and olivine, with the exact proportions depending on the magma composition.

One of the most important and dangerous components of volcanic ash is crystalline silica, which can appear as quartz, cristobalite, or tridymite (Horwell & Baxter, 2006). Cristobalite is considered the most toxic of these forms and is particularly common in volcanoes. It forms through a process called devitrification, the conversion of volcanic glass into crystalline material (Horwell & Baxter, 2006).

Aside from crystalline silica, volcanic ash also carries a range of trace elements and chemical species on its surface (Durant et al., 2010). During an eruption, gases such as fluorine, sulfur dioxide, and hydrogen chloride interact with ash particles, leaving chemical coatings on the surface of the ash (Durant et al., 2010). These surface chemicals can be rapidly released when ash comes into contact with water, contaminating water supplies and soil environments. The presence of iron on ash surfaces is also significant, as it can generate harmful free radicals when it interacts with the lung, potentially causing cell damage even in ash that contains little to no crystalline silica (Horwell & Baxter, 2006).

== Notable Volcanic Eruptions ==

=== 3.1 Mount St. Helens ===
[[File:Vhp img571.jpg|thumb|Mout St. Helens eruption on May 18, 1980, showing the volcanic ash plume produced during the eruption. Source: U.S. Geological Survey (Public Domain).]]
The eruption of Mount St. Helen in Washington, USA, on May 19, 1980, is considered one of the most significant volcanic eruptions in modern history. Following a magnitude 5.1 earthquake, the volcano experienced a lateral blast that destroyed large areas surrounding the mountain. The eruption produced approximately 540 million tons of volcanic ash, which spread across much of the United States and even circled the globe within weeks. The eruption produced a large ash cloud that caused transportation disruptions, environmental damage, and respiratory health concerns (U.S. Geological Survey [USGS], 2023). The event demonstrated how volcanic ash can affect areas far beyond the immediate vicinity of a volcano and remains an important case study for volcanic hazard research.

=== 3.2 Comparison of Major Ash- Producing Eruption ===
Several volcanic eruptions have produced significant amounts of ash, including Mount St. Helens (1980), Mount Pinatubo (1991), and Eyjafjallajökull (2010). While Mount St. Helens caused major regional impacts, Mount Pinatubo had global climate effects due to the large volume of ash and gas released into the atmosphere. In contrast Eyjafjallajökull primarily disrupted air travel across Europe. These eruptions highlight the diverse environmental health and economic impacts that volcanic ash can produce (Newhall & Punongbayan, 1997).

== Effects on Human Health ==

=== 4.1 Respiratory Effects ===
[[File:LungDiagram.jpg|thumb|The human respiratory system, specifically the Alveoli. Source: Canadian Lung Association]]
The respiratory systems are direct targets for volcanic ash due to the ease of inhalation of these tiny particles and their sheer abundance when released. Respirable particles are of greatest concern. These respirable particles, due to their size of around 1/20th the width of a human hair, are capable of being suspended in the air for an extensive amount of time (Shezi et al., 2020). Because of this size, they are fine enough to penetrate deep into the alveolar region of the lungs, where they have the greatest toxic potential (Horwell & Baxter, 2006).

Once these particles reach these alveloar regions, they interact with the cells of the immune system. Resident macrophages and mast cells act as the first line of defense, the primary response, to the inhaled particles. These immune cells are working hard, engulfing these particles, in a process named phagocytosis. The issue is that, when volcanoes release volcanic ash, it does not release only a few particles. The large quantities of ash that are present in the air after an eruption, and the amount of particles inhaled at once, make it difficult for macrophages and mast cells to remove all of them. Due to this, there is a release of cytokines that aim to recruit other immune cells to initiate the second line of defense, but this results in inflammation. This inflammatory response that occurs leads to unwanted effects of swelling or irritation in the lungs that causes coughing or shortness of breath (Horwell & Baxter, 2006).

In addition to these respirable particles, exposure to crystalline silica has been studied throughout occupational medicine and has been determined as a cause of silicosis, a serious fibrotic lung disease, and prolonged exposure may also increase the risk of lung cancer (Horwell & Baxter, 2006). This makes the crystalline silica content of ash one of the most critical factors in assessing its health hazard. Repeated exposure to these particles like seen in the Mount St. Helen's eruption can cause chronic respiratory damage.

=== 4.2 Eye and Skin Irritation ===
Volcanic ash also has the ability to impact the eyes and skin. Volcanic ash frequently contains sharp objects that are able to scratch sensitive surfaces when they come into contact. The eyes being exposed to these volcanic ash particles is said to cause unfavourable symptoms like corneal abrasions or scratches, which can cause severe eye pain, conjunctivitis, and more. The skin is also another surface that volcanic ash can attack. When ash comes into contact with the skin, it can cause irritation and reddening of the skin (U.S. Geological Survey).

=== 4.3 Immune Systems ===
The impacts of volcanic ash exposure are noticeable on both the respiratory and eye and skin levels. But the impacts of volcanic ash are able to go beyond and are shown to damage the immune system as a whole. As mentioned before, the primary and secondary responses are how the body is able to fight off bacteria that manage to enter to prevent infections from occurring. What is interesting is that it has been shown that the properties of volcanic ash may play a role in interfering with these systems (Monick et al., 2013).

Macrophages, the first line of defense, play a role in engulfing foreign particles in a process named phagocytosis. Research shows that volcanic ash is actually able to impair macrophages from performing their task, resulting in a reduced ability to remove these foreign particles (Monick et al., 2013). This reduced ability allows for more particles to be present in the body, increasing the chances of infection and other negative effects.

With volcanic ash carrying a range of trace elements like iron, it can actually provide a source of nutrients that bacteria can use to grow and survive inside the body (Monick et al., 2013).

== Effects on Microbial Ecosystem ==

=== 5.1 Soil Microbial Communities ===
[[File:Soilrecovery.jpg|thumb|363x363px|The process by which volcanic ash impacts soil environments over time. Source: (Fiantis et al., 2019).]]
Volcanic ash can significantly affect soil microbial communities by altering soil chemistry, pH, moisture retention, and nutrient availability. Immediately after an eruption, a thick layer of ash may reduce microbial activity by covering existing soil and limiting access to oxygen and different organic matter. As a result, the abundance and diversity of microorganisms often decrease in the short term (Fiantis et al., 2019).

However, volcanic ash also contains minerals such as iron, magnesium, potassium, and phosphorus that can gradually improve soil fertility. As weathering occurs, these nutrients are released into the soil and become available to microorganisms. Certain bacteria and fungi are able to colonize newly formed volcanic deposits and play an important role in breaking down minerals, cycling nutrients, and supporting soil development. Over time, microbial communities help create conditions that allow plants and other organisms to establish themselves, contributing to ecosystem recovery (Fiantis et al., 2019).

Volcanic ash can have both positive and negative impacts on soil microbial ecosystems, depending on whether the effects are considered in the short term or the long term.

=== 5.2 Water Contamination ===
Volcanic ash can enter rivers, lakes, and groundwater through rainfall. Ash particles may increase water turbidity and alter water chemistry, affecting microorganisms that live in aquatic environments. Also, high concentrations of ash can reduce light penetration and disrupt microbial processes that are important for maintaining water quality and ecosystem health (Stewart et al, 2006).

Furthermore, volcanic ash may change the chemical composition of water by releasing minerals and other substances. These changes can alter the balance of microbial communities, causing some species to decline while others become more abundant. As a result, normal nutrient cycling and other ecological processes carried out by microorganisms may be disrupted until the ecosystem gradually recovers (Stewart et al., 2006).

=== 5.3 Recovery and Adaptation ===
Although volcanic eruptions can initially disrupt microbial ecosystems, many microorganisms are capable of adapting to the new environmental conditions. Over time, microbial communities recolonize ash- covered areas and contribute to soil formation and nutrient cycling. This recovery process helps establish conditions that support plant growth and the gradual restoration of affected ecosystems (Fiantis et al., 2019).

== Interconnections Between Human Health and Microbial Ecosystem ==
[[File:Volcanic_ash_infographic.jpg|thumb|516x516px|Volcanic ash and its connections infographic. Source: (OpenAI, 2026)]]
When volcanic ash is deposited onto soil and water environments, it does not settle as an inert layer. Instead, it restructures the chemical and biological conditions of the microbial communities in that area. Ash alters the carbon and nitrogen concentrations in the soil, changes the pH, and introduces new minerals and trace elements, thereby affecting which microorganisms survive and thrive (Maltz et al., 2024). Various studies were conducted following the 1980 eruption of Mount St. Helens. These studies showed that microbial communities remained fundamentally restructured for decades, with bacterial and fungal composition varying significantly with ashfall intensity and soil chemistry (Maltz et al., 2024). Along with these studies, research on volcanic ash fertilization was also being conducted. These studies showed that once ash concentrations pass a certain threshold, the soil microbiome shifts. Some bacteria that may help plants grow actually increase, while others decline. This suggests ash doesn't just kill off microbial life, it reorganizes it in complex ways (Staudigel et al., 2025). These shifts matter because soil microorganisms are responsible for nearly all biogeochemical transformations, including nutrient cycling, soil formation, and organic matter decomposition, meaning that disruptions to microbial communities have cascading effects on the broader ecosystem (Staudigel et al., 2025).

These environmental changes caused by ashfall do not stay contained in the soil. They also extend into water systems, such as rivers, lakes, and reservoirs, and ultimately reach human homes and human systems. When ash falls into water supplies, it increases acidity and releases soluble contaminants, including fluoride, iron, sulphate, and chloride, into drinking water (Stewart et al., 2006). It also increases turbidity, which is dangerous because the ash particles present interfere with the disinfection process, allowing harmful bacteria to survive in the water (Stewart et al., 2006). This raises the risk of waterborne disease outbreaks (Stewart et al., 2006). Aside from water contamination, the restructuring of soil microbial communities also affects food systems. Changes in soil chemistry disrupt nutrient cycling, which reduces soil fertility and can lower crop yields. On top of this, volcanic air pollution has been linked to respiratory illness, cardiovascular effects, and increased healthcare visits in exposed populations (Stewart et al., 2022). This shows that the path from environmental disruption to human health outcomes works through several pathways at once, not just one (Stewart et al., 2022). Together, these interconnections show that the health impacts of volcanic ash cannot be understood by looking at geology, microbiology, or human health on their own; they are fundamentally linked.
== Conclusion ==
Understanding volcanic ash requires integrating geology, microbiology, and statistics, as each discipline provides insights into how eruptions affect ecosystems and human health. This project demonstrated that volcanic eruptions extend far beyond a single geological area; their impacts travel through surrounding ecosystems and human populations in ways that can only be fully understood through an integrated approach.

Volcanic ash composition, shaped by magma type and eruption style, determines how hazardous it is. Fine particles and crystalline silica content are contributors to acute respiratory effects and long-term disease risk. However, ash does not harm humans alone. Once deposited in soil and water, it restructures entire microbial communities and alters pH levels, altering the balance of bacteria and fungi that support ecosystem recovery. These changes stay in the ecosystem and persist for decades, as shown by Mount St. Helens. Understanding these effects requires quantitative methods: statistical analysis of data, probabilistic risk assessment models, and grain-size characterization across eruptions translate geological hazards into public health predictions. It also requires a deep understanding of microbial systems and how the exposure affects them.

This integration of geology, microbiology, and statistics shows how modern science can work together to tackle real-world problems. Problems that seem purely geological, such as volcanic hazards, cannot be solved by geologists alone. Instead, they require microbiologists to understand ecosystem recovery and statisticians to quantify health risks and inform policy. For those pursuing careers in these fields, volcanic ash demonstrates why interdisciplinary collaboration matters and contributes to meaningful work in environmental health, climate adaptation, and disaster risk reduction.

==References==
<references />
Baxter, P. J., Ing, R., Falk, H., & Plikaytis, B. (1983). Mount St. Helens eruptions: The acute respiratory effects of volcanic ash in a North American community. Archives of Environmental Health, 38(3), 138–143. https://doi.org/10.1080/00039896.1983.10543892

Canadian Lung Association. ''Your lungs'' [Image]. Canadian Lung Association. <nowiki>https://www.lung.ca/how-to-protect-your-lungs/your-lungs/</nowiki>

Durant, A. J., Bonadonna, C., & Horwell, C. J. (2010). Atmospheric and Environmental Impacts of Volcanic Particulates. Elements, 6(4), 235–240. https://doi.org/10.2113/gselements.6.4.235

Fiantis, D., Ginting, F. I., Gusnidar, Nelson, M., & Minasny, B. (2019). ''Volcanic ash, insecurity for the people but securing fertile soil for the future''. ''Sustainability, 11''(11), 3072. <nowiki>https://doi.org/10.3390/su11113072</nowiki>

Fiantis, D., Ginting, F. I., Gusnidar, G., Nelson, M., & Van Ranst, E. (2019). ''Volcanic ash, soil formation, and ecosystem development.''

Horwell, C. J., & Baxter, P. J. (2006). The respiratory health hazards of volcanic ash: a review for volcanic risk mitigation. Bulletin of Volcanology, 69(1), 1–24. https://doi.org/10.1007/s00445-006-0052-y

Maltz, M.R., Allen, M.F., Phillips, M.L., Hernandez, R.R., Shulman, H.B., Freund, L., Andrews, L.V., Botthoff, J.K., and Aronson, E.L. (2024). Microbial community structure in recovering forests of Mount St. Helens. Frontiers in Microbiomes, 3, 1399416. https://doi.org/10.3389/frmbi.2024.1399416

Monick, M. M., Baltrusaitis, J., Powers, L. S., Borcherding, J. A., Caraballo, J. C., Mudunkotuwa, I., Peate, D. W., Walters, K., Thompson, J. M., Grassian, V. H., Gudmundsson, G., & Comellas, A. P. (2013). Effects of Eyjafjallajökull Volcanic Ash on Innate Immune System Responses and Bacterial Growth in Vitro. ''Environmental Health Perspectives'', ''121''(6), 691–698. https://doi.org/10.1289/ehp.1206004.

Newhall, C. G., & Punongbayan, R. S. (1997). ''The cataclysmic 1991 eruption of Mount Pinatubo, Philippines''. U.S. Geological Survey Fact Sheet 113-97.

OpenAI. (2026). ''Connections with volcanic ash'' [AI-generated image]. ChatGPT. <nowiki>https://chatgpt.com‌</nowiki>{{Projectbox_EOSC311}}
[[Category:EOSC311]]

Shezi, B., Mathee, A., Cele, N., Ndabandaba, S., & Street, R. A. (2020). Occupational Exposure to Fine Particulate Matter (PM4 and PM2.5) during Hand-Made Cookware Operation: Personal, Indoor and Outdoor Levels. International journal of environmental research and public health, 17(20), 7522. <nowiki>https://doi.org/10.3390/ijerph17207522</nowiki>

Staudigel, H., et al. (2025). Tripled plant productivity and soil microbiome restructuring in a greenhouse volcanic ash fertilization experiment. Ecosphere, 16(9), e70406. https://doi.org/10.1002/ecs2.70406

Stewart, C., Johnston, D. M., Leonard, G. S., Horwell, C. J., Thordarson, T., & Cronin, S. J. (2006). ''Contamination of water supplies by volcanic ashfall: A literature review and simple impact modelling.''

U.S. Geological Survey. (n.d.). ''Volcanic ash impacts & mitigation: Eyes and skin''. U.S. Department of the Interior. <nowiki>https://volcanoes.usgs.gov/volcanic_ash/eye_skin.html</nowiki>

U.S. Geological Survey. (2023). ''1980 Cataclysmic Eruption''. Retrieved from <nowiki>https://www.usgs.gov/volcanoes/mount-st.-helens/science/1980-cataclysmic-eruption</nowiki>

U.S. Geological Survey. (2017, December 13). ''Illustration of the basic process of magma formation, movement to the surface, and eruption through a volcanic vent'' [Illustration]. <nowiki>https://www.usgs.gov/media/images/illustration-basic-process-magma-formation-movement-s</nowiki>

U.S. Geological Survey. (2015, November 13). ''Scanning electron microscope image of volcanic ash'' [Photograph]. <nowiki>https://www.usgs.gov/media/images/scanning-electron-microscope-image-volcanic-ash</nowiki>

== Group Contributions and AI Use ==

'''Group Contributions:'''
* Nyamat: Section 2 (Volcanic Ash Composition), Section 6 (Interconnections), and Conclusion
* Raj: Introduction and Section 4 (Effects on Human Health)
* Eric: Section 3 (Notable Volcanic Eruptions) and Section 5 (Effects on Microbial Ecosystems)

'''AI Use Statement:'''
Used Grammarly to revise grammar and spelling throughout the article. Used OpenAI to generate templates for diagrams.

Course:EOSC311/2026/Volcanic Ash Composition and its effects on Human Health and Microbial Ecosystems

2026-06-18T03:36:11Z

RAJMEHRA: changes

== Introduction ==
Volcanic eruptions are mighty natural forces that are able to cause vast changes in ecosystems and the atmosphere. Volcanoes, when they erupt, release large amounts of volcanic ash, volcanic gases, and fragments of rocks that are able to be spread over long distances through many mediums like wind and water, affecting not only local but also global scales. Most of the time, volcanoes are talked about from a geological perspective, but the impacts of volcanoes go beyond simple things like land creation. Volcanic emissions can have an influence on air, water, and soil quality that can have an impact on both human health and the microbial ecosystem. This project looks at the connections between volcanic geology, human health and microbiology by exploring how volcanic ash materials have an impact on respiratory and immune systems, as well as microbial ecosystems.

==Volcanic Ash Composition==

=== 2.1 Formation of Volcanic Ash ===
[[File:VolcanoImage.jpg|thumb|The process by which volcanic ash forms, starting from magma ascending from the mantle to the surface of the Earth. Source: U.S. Geological Survey (Public Domain).]]
Magma is molten rock found beneath the Earth's surface that contains dissolved gases, including water vapor, carbon dioxide (CO₂), and sulfur dioxide (SO₂). As magma rises toward the surface, pressure decreases, causing these gases to escape and form bubbles known as vesicles, similar to how a carbonated drink fizzes when opened. When magma rises quickly, pressure builds up inside these bubbles until they burst, breaking the magma into fine particles known as volcanic ash (Durant et al., 2010). The composition of the magma affects how explosive the eruption is — magmas with high silica content tend to erupt more explosively, producing larger amounts of ash.
=== 2.2 Particle Size and Structure ===
During an explosive volcanic eruption, rocks, mineral fragments, and/or ash are ejected into the air; these are known as pyroclasts. [[File:Respirable Material Content in Volcanic Ash from Major Eruptions.jpg|thumb|400px|Table 1. Respirable material (<4 μm) content in ash from nine historical eruptions. Adapted from Horwell & Baxter (2006).]] Volcanic ash is defined as pyroclasts with a diameter of 2mm or less, an important factor in determining how hazardous the ash is to human health. The size is measured using aerodynamic diameter, and particles are classified into two key health-relevant categories: thoracic particles (PM10), which are less than 10 μm in diameter, and respirable particles (PM4), which are less than 4 μm in diameter (Horwell & Baxter, 2006). The percentage of respirable material in ash varies considerably depending on the volcano, the explosivity of the eruption, and the distance from the vent at which ash is collected (Horwell & Baxter, 2006).
[[File:VolcanicAsh.jpg|thumb|The shape and size of volcanic ash under a microscope with a 50 micrometre scale bar. Source: U.S. Geological Survey (Public Domain).]]
As shown in Table 1, the proportion of respirable material varies across eruptions, with no clear relationship to the Volcanic Explosivity Index (VEI). For example, Pinatubo's 1991 eruption had the highest VEI of the group (6) but a comparatively low respirable fraction (9.8%), while Mount St. Helens and Vesuvius, both with a VEI of 5, produced different proportions (11.7% and 16.9%, respectively). This suggests that the explosivity of an eruption alone does not determine how hazardous its ash will be to human health; other factors, such as magma composition and fragmentation style, likely play a larger role in generating fine, respirable particles.

Fine ash particles tend to fall in loose clusters of less than 100 μm, which break apart easily when they hit the ground or when they get disturbed by external factors, such as wind, passing vehicles, or everyday human activity (Horwell & Baxter, 2006). This means that ash that has already settled on the ground can be lifted back into the air and inhaled all over again, making exposure an ongoing cycle even after an eruption has ended. The irregular shape of these particles also makes them more physically damaging once inhaled, as their sharp edges can irritate and damage the lining of the airways (Horwell & Baxter, 2006). Together, these structural properties, combined with how small respirable particles are, make volcanic ash particularly harmful to the respiratory system.

=== 2.3 Chemical and Mineral Composition ===
Volcanic ash is not made up from a single uniform material; its chemical and mineral composition varies depending on the type of magma that erupted and the nature of the eruption. Ash is made up of three main components: glass, which is a quenched (rapidly cooled) melt; lithic fragments, which are pieces of pre-existing rock from the volcanic vent; and crystals, which are minerals that formed within the magma before the eruption (Durant et al., 2010). The crystal component can include minerals such as quartz, feldspar, pyroxenes, amphiboles, and olivine, with the exact proportions depending on the magma composition.

One of the most important and dangerous components of volcanic ash is crystalline silica, which can appear as quartz, cristobalite, or tridymite (Horwell & Baxter, 2006). Cristobalite is considered the most toxic of these forms and is particularly common in volcanoes. It forms through a process called devitrification, the conversion of volcanic glass into crystalline material (Horwell & Baxter, 2006).

Aside from crystalline silica, volcanic ash also carries a range of trace elements and chemical species on its surface (Durant et al., 2010). During an eruption, gases such as fluorine, sulfur dioxide, and hydrogen chloride interact with ash particles, leaving chemical coatings on the surface of the ash (Durant et al., 2010). These surface chemicals can be rapidly released when ash comes into contact with water, contaminating water supplies and soil environments. The presence of iron on ash surfaces is also significant, as it can generate harmful free radicals when it interacts with the lung, potentially causing cell damage even in ash that contains little to no crystalline silica (Horwell & Baxter, 2006).

== Notable Volcanic Eruptions ==

=== 3.1 Mount St. Helens ===
[[File:Vhp img571.jpg|thumb|Mout St. Helens eruption on May 18, 1980, showing the volcanic ash plume produced during the eruption. Source: U.S. Geological Survey (Public Domain).]]
The eruption of Mount St. Helen in Washington, USA, on May 19, 1980, is considered one of the most significant volcanic eruptions in modern history. Following a magnitude 5.1 earthquake, the volcano experienced a lateral blast that destroyed large areas surrounding the mountain. The eruption produced approximately 540 million tons of volcanic ash, which spread across much of the United States and even circled the globe within weeks. The eruption produced a large ash cloud that caused transportation disruptions, environmental damage, and respiratory health concerns (U.S. Geological Survey [USGS], 2023). The event demonstrated how volcanic ash can affect areas far beyond the immediate vicinity of a volcano and remains an important case study for volcanic hazard research.

=== 3.2 Comparison of Major Ash- Producing Eruption ===
Several volcanic eruptions have produced significant amounts of ash, including Mount St. Helens (1980), Mount Pinatubo (1991), and Eyjafjallajökull (2010). While Mount St. Helens caused major regional impacts, Mount Pinatubo had global climate effects due to the large volume of ash and gas released into the atmosphere. In contrast Eyjafjallajökull primarily disrupted air travel across Europe. These eruptions highlight the diverse environmental health and economic impacts that volcanic ash can produce (Newhall & Punongbayan, 1997).

== Effects on Human Health ==

=== 4.1 Respiratory Effects ===
[[File:LungDiagram.jpg|thumb|The human respiratory system, specifically the Alveoli. Source: Canadian Lung Association]]
The respiratory systems are direct targets for volcanic ash due to the ease of inhalation of these tiny particles and their sheer abundance when released. Respirable particles are of greatest concern. These respirable particles, due to their size of around 1/20th the width of a human hair, are capable of being suspended in the air for an extensive amount of time (Shezi et al., 2020). Because of this size, they are fine enough to penetrate deep into the alveolar region of the lungs, where they have the greatest toxic potential (Horwell & Baxter, 2006).

Once these particles reach these alveloar regions, they interact with the cells of the immune system. Resident macrophages and mast cells act as the first line of defense, the primary response, to the inhaled particles. These immune cells are working hard, engulfing these particles, in a process named phagocytosis. The issue is that, when volcanoes release volcanic ash, it does not release only a few particles. The large quantities of ash that are present in the air after an eruption, and the amount of particles inhaled at once, make it difficult for macrophages and mast cells to remove all of them. Due to this, there is a release of cytokines that aim to recruit other immune cells to initiate the second line of defense, but this results in inflammation. This inflammatory response that occurs leads to unwanted effects of swelling or irritation in the lungs that causes coughing or shortness of breath (Horwell & Baxter, 2006).

In addition to these respirable particles, exposure to crystalline silica has been studied throughout occupational medicine and has been determined as a cause of silicosis, a serious fibrotic lung disease, and prolonged exposure may also increase the risk of lung cancer (Horwell & Baxter, 2006). This makes the crystalline silica content of ash one of the most critical factors in assessing its health hazard. Repeated exposure to these particles (like seen in people from these volcanic regions that we mentioned above?) can cause chronic respiratory damage.

=== 4.2 Eye and Skin Irritation ===
Volcanic ash also has the ability to impact the eyes and skin. Volcanic ash frequently contains sharp objects that are able to scratch sensitive surfaces when they come into contact. The eyes being exposed to these volcanic ash particles is said to cause unfavourable symptoms like corneal abrasions or scratches, which can cause severe eye pain, conjunctivitis, and more. The skin is also another surface that volcanic ash can attack. When ash comes into contact with the skin, it can cause irritation and reddening of the skin (U.S. Geological Survey).

=== 4.3 Immune Systems ===
The impacts of volcanic ash exposure are noticeable on both the respiratory and eye and skin levels. But the impacts of volcanic ash are able to go beyond and are shown to damage the immune system as a whole. As mentioned before, the primary and secondary responses are how the body is able to fight off bacteria that manage to enter to prevent infections from occurring. What is interesting is that it has been shown that the properties of volcanic ash may play a role in interfering with these systems (Monick et al., 2013).

Macrophages, the first line of defense, play a role in engulfing foreign particles in a process named phagocytosis. Research shows that volcanic ash is actually able to impair macrophages from performing their task, resulting in a reduced ability to remove these foreign particles (Monick et al., 2013). This reduced ability allows for more particles to be present in the body, increasing the chances of infection and other negative effects.

With volcanic ash carrying a range of trace elements like iron, it can actually provide a source of nutrients that bacteria can use to grow and survive inside the body (Monick et al., 2013).

== Effects on Microbial Ecosystem ==

=== 5.1 Soil Microbial Communities ===
[[File:Soilrecovery.jpg|thumb|363x363px|The process by which volcanic ash impacts soil environments over time. Source: (Fiantis et al., 2019).]]
Volcanic ash can significantly affect soil microbial communities by altering soil chemistry, pH, moisture retention, and nutrient availability. Immediately after an eruption, a thick layer of ash may reduce microbial activity by covering existing soil and limiting access to oxygen and different organic matter. As a result, the abundance and diversity of microorganisms often decrease in the short term (Fiantis et al., 2019).

However, volcanic ash also contains minerals such as iron, magnesium, potassium, and phosphorus that can gradually improve soil fertility. As weathering occurs, these nutrients are released into the soil and become available to microorganisms. Certain bacteria and fungi are able to colonize newly formed volcanic deposits and play an important role in breaking down minerals, cycling nutrients, and supporting soil development. Over time, microbial communities help create conditions that allow plants and other organisms to establish themselves, contributing to ecosystem recovery (Fiantis et al., 2019).

Volcanic ash can have both positive and negative impacts on soil microbial ecosystems, depending on whether the effects are considered in the short term or the long term.

=== 5.2 Water Contamination ===
Volcanic ash can enter rivers, lakes and ground water through rainfall. Ash particles may increase water turbidity and alter water chemistry, affecting microorganisms that live in aquatic environments. Also, high concentrations of ash can reduce light penetration anddisirupt microbial processes that are important for maintaining water quality and ecosystem health (Stewart et al, 2006).

Furthermore, volcanic ash may change the chemical composition of water by releasing minerals and other substances. These changes can alter the balance of microbial communities, causing some species to decline while others become more abundant. As a result normal nutrient cycling and other ecological processes carried out by microorganisms may be disrupted until the ecosystem gradually recovers (Stewart et al., 2006).

=== 5.3 Recovery and Adaptation ===
Although volcanic eruptions can initially disrupt microbial ecosystems, many microorganisms are capable of adapting to the new environmental conditions. Over time, microbial communities recolonize ash- covered areas and contribute to soil formation and nutrient cycling. This recovery process helps establish conditions that support plant growth and the gradual restoration of affected ecosystems (Fiantis et al., 2019).

== Interconnections Between Human Health and Microbial Ecosystem ==
[[File:Volcanic_ash_infographic.jpg|thumb|516x516px|Volcanic ash and its connections infographic. Source: (OpenAI, 2026)]]
When volcanic ash is deposited onto soil and water environments, it does not settle as an inert layer. Instead, it restructures the chemical and biological conditions of the microbial communities in that area. Ash alters the carbon and nitrogen concentrations in the soil, changes the pH, and introduces new minerals and trace elements, thereby affecting which microorganisms survive and thrive (Maltz et al., 2024). Various studies were conducted following the 1980 eruption of Mount St. Helens. These studies showed that microbial communities remained fundamentally restructured for decades, with bacterial and fungal composition varying significantly with ashfall intensity and soil chemistry (Maltz et al., 2024). Along with these studies, research on volcanic ash fertilization was also being conducted. These studies showed that once ash concentrations pass a certain threshold, the soil microbiome shifts. Some bacteria that may help plants grow actually increase, while others decline. This suggests ash doesn't just kill off microbial life, it reorganizes it in complex ways (Staudigel et al., 2025). These shifts matter because soil microorganisms are responsible for nearly all biogeochemical transformations, including nutrient cycling, soil formation, and organic matter decomposition, meaning that disruptions to microbial communities have cascading effects on the broader ecosystem (Staudigel et al., 2025).

These environmental changes caused by ashfall do not stay contained in the soil. They also extend into water systems, such as rivers, lakes, and reservoirs, and ultimately reach human homes and human systems. When ash falls into water supplies, it increases acidity and releases soluble contaminants, including fluoride, iron, sulphate, and chloride, into drinking water (Stewart et al., 2006). It also increases turbidity, which is dangerous because the ash particles present interfere with the disinfection process, allowing harmful bacteria to survive in the water (Stewart et al., 2006). This raises the risk of waterborne disease outbreaks (Stewart et al., 2006). Aside from water contamination, the restructuring of soil microbial communities also affects food systems. Changes in soil chemistry disrupt nutrient cycling, which reduces soil fertility and can lower crop yields. On top of this, volcanic air pollution has been linked to respiratory illness, cardiovascular effects, and increased healthcare visits in exposed populations (Stewart et al., 2022). This shows that the path from environmental disruption to human health outcomes works through several pathways at once, not just one (Stewart et al., 2022). Together, these interconnections show that the health impacts of volcanic ash cannot be understood by looking at geology, microbiology, or human health on their own; they are fundamentally linked.
== Conclusion ==
Understanding volcanic ash requires integrating geology, microbiology, and statistics, as each discipline provides insights into how eruptions affect ecosystems and human health. This project demonstrated that volcanic eruptions extend far beyond a single geological area; their impacts travel through surrounding ecosystems and human populations in ways that can only be fully understood through an integrated approach.

Volcanic ash composition, shaped by magma type and eruption style, determines how hazardous it is. Fine particles and crystalline silica content are contributors to acute respiratory effects and long-term disease risk. However, ash does not harm humans alone. Once deposited in soil and water, it restructures entire microbial communities and alters pH levels, altering the balance of bacteria and fungi that support ecosystem recovery. These changes stay in the ecosystem and persist for decades, as shown by Mount St. Helens. Understanding these effects requires quantitative methods: statistical analysis of data, probabilistic risk assessment models, and grain-size characterization across eruptions translate geological hazards into public health predictions. It also requires a deep understanding of microbial systems and how the exposure affects them.

==References==
<references />
Baxter, P. J., Ing, R., Falk, H., & Plikaytis, B. (1983). Mount St. Helens eruptions: The acute respiratory effects of volcanic ash in a North American community. Archives of Environmental Health, 38(3), 138–143. https://doi.org/10.1080/00039896.1983.10543892

Durant, A. J., Bonadonna, C., & Horwell, C. J. (2010). Atmospheric and Environmental Impacts of Volcanic Particulates. Elements, 6(4), 235–240. https://doi.org/10.2113/gselements.6.4.235

Fiantis, D., Ginting, F. I., Gusnidar, G., Nelson, M., & Van Ranst, E. (2019). ''Volcanic ash, soil formation, and ecosystem development.''

Horwell, C. J., & Baxter, P. J. (2006). The respiratory health hazards of volcanic ash: a review for volcanic risk mitigation. Bulletin of Volcanology, 69(1), 1–24. https://doi.org/10.1007/s00445-006-0052-y

Newhall, C. G., & Punongbayan, R. S. (1997). ''The cataclysmic 1991 eruption of Mount Pinatubo, Philippines''. U.S. Geological Survey Fact Sheet 113-97.

Maltz, M.R., Allen, M.F., Phillips, M.L., Hernandez, R.R., Shulman, H.B., Freund, L., Andrews, L.V., Botthoff, J.K., and Aronson, E.L. (2024). Microbial community structure in recovering forests of Mount St. Helens. Frontiers in Microbiomes, 3, 1399416. https://doi.org/10.3389/frmbi.2024.1399416

Monick, M. M., Baltrusaitis, J., Powers, L. S., Borcherding, J. A., Caraballo, J. C., Mudunkotuwa, I., Peate, D. W., Walters, K., Thompson, J. M., Grassian, V. H., Gudmundsson, G., & Comellas, A. P. (2013). Effects of Eyjafjallajökull Volcanic Ash on Innate Immune System Responses and Bacterial Growth in Vitro. ''Environmental Health Perspectives'', ''121''(6), 691–698. https://doi.org/10.1289/ehp.1206004.

Shezi, B., Mathee, A., Cele, N., Ndabandaba, S., & Street, R. A. (2020). Occupational Exposure to Fine Particulate Matter (PM4 and PM2.5) during Hand-Made Cookware Operation: Personal, Indoor and Outdoor Levels. International journal of environmental research and public health, 17(20), 7522. <nowiki>https://doi.org/10.3390/ijerph17207522</nowiki>

Stewart, C., Johnston, D. M., Leonard, G. S., Horwell, C. J., Thordarson, T., & Cronin, S. J. (2006). ''Contamination of water supplies by volcanic ashfall: A literature review and simple impact modelling.''

U.S. Geological Survey. (n.d.). ''Volcanic ash impacts & mitigation: Eyes and skin''. U.S. Department of the Interior. <nowiki>https://volcanoes.usgs.gov/volcanic_ash/eye_skin.html</nowiki>

U.S. Geological Survey. (2023). ''1980 Cataclysmic Eruption''. Retrieved from <nowiki>https://www.usgs.gov/volcanoes/mount-st.-helens/science/1980-cataclysmic-eruption</nowiki>

Canadian Lung Association. ''Your lungs'' [Image]. Canadian Lung Association. <nowiki>https://www.lung.ca/how-to-protect-your-lungs/your-lungs/</nowiki>

U.S. Geological Survey. (2017, December 13). ''Illustration of the basic process of magma formation, movement to the surface, and eruption through a volcanic vent'' [Illustration]. <nowiki>https://www.usgs.gov/media/images/illustration-basic-process-magma-formation-movement-s</nowiki>

U.S. Geological Survey. (2015, November 13). ''Scanning electron microscope image of volcanic ash'' [Photograph]. <nowiki>https://www.usgs.gov/media/images/scanning-electron-microscope-image-volcanic-ash</nowiki>

Fiantis, D., Ginting, F. I., Gusnidar, Nelson, M., & Minasny, B. (2019). ''Volcanic ash, insecurity for the people but securing fertile soil for the future''. ''Sustainability, 11''(11), 3072. <nowiki>https://doi.org/10.3390/su11113072</nowiki>

OpenAI. (2026). ''Connections with volcanic ash'' [AI-generated image]. ChatGPT. <nowiki>https://chatgpt.com‌</nowiki>{{Projectbox_EOSC311}}
[[Category:EOSC311]]

Course:EOSC311/2026/Volcanic Ash Composition and its effects on Human Health and Microbial Ecosystems

2026-06-18T03:32:16Z

RAJMEHRA: image

== Introduction ==
Volcanic eruptions are mighty natural forces that are able to cause vast changes in ecosystems and the atmosphere. Volcanoes, when they erupt, release large amounts of volcanic ash, volcanic gases, and fragments of rocks that are able to be spread over long distances through many mediums like wind and water, affecting not only local but also global scales. Most of the time, volcanoes are talked about from a geological perspective, but the impacts of volcanoes go beyond simple things like land creation. Volcanic emissions can have an influence on air, water, and soil quality that can have an impact on both human health and the microbial ecosystem. This project looks at the connections between volcanic geology, human health and microbiology by exploring how volcanic ash materials have an impact on respiratory and immune systems, as well as microbial ecosystems.

==Volcanic Ash Composition==

=== 2.1 Formation of Volcanic Ash ===
[[File:VolcanoImage.jpg|thumb|The process by which volcanic ash forms, starting from magma ascending from the mantle to the surface of the Earth. Source: U.S. Geological Survey (Public Domain).]]
Magma is molten rock found beneath the Earth's surface that contains dissolved gases, including water vapor, carbon dioxide (CO₂), and sulfur dioxide (SO₂). As magma rises toward the surface, pressure decreases, causing these gases to escape and form bubbles known as vesicles, similar to how a carbonated drink fizzes when opened. When magma rises quickly, pressure builds up inside these bubbles until they burst, breaking the magma into fine particles known as volcanic ash (Durant et al., 2010). The composition of the magma affects how explosive the eruption is — magmas with high silica content tend to erupt more explosively, producing larger amounts of ash.
=== 2.2 Particle Size and Structure ===
During an explosive volcanic eruption, rocks, mineral fragments, and/or ash are ejected into the air; these are known as pyroclasts. [[File:Respirable Material Content in Volcanic Ash from Major Eruptions.jpg|thumb|400px|Table 1. Respirable material (<4 μm) content in ash from nine historical eruptions. Adapted from Horwell & Baxter (2006).]] Volcanic ash is defined as pyroclasts with a diameter of 2mm or less, an important factor in determining how hazardous the ash is to human health. The size is measured using aerodynamic diameter, and particles are classified into two key health-relevant categories: thoracic particles (PM10), which are less than 10 μm in diameter, and respirable particles (PM4), which are less than 4 μm in diameter (Horwell & Baxter, 2006). The percentage of respirable material in ash varies considerably depending on the volcano, the explosivity of the eruption, and the distance from the vent at which ash is collected (Horwell & Baxter, 2006).
[[File:VolcanicAsh.jpg|thumb|The shape and size of volcanic ash under a microscope with a 50 micrometre scale bar. Source: U.S. Geological Survey (Public Domain).]]
As shown in Table 1, the proportion of respirable material varies across eruptions, with no clear relationship to the Volcanic Explosivity Index (VEI). For example, Pinatubo's 1991 eruption had the highest VEI of the group (6) but a comparatively low respirable fraction (9.8%), while Mount St. Helens and Vesuvius, both with a VEI of 5, produced different proportions (11.7% and 16.9%, respectively). This suggests that the explosivity of an eruption alone does not determine how hazardous its ash will be to human health; other factors, such as magma composition and fragmentation style, likely play a larger role in generating fine, respirable particles.

Fine ash particles tend to fall in loose clusters of less than 100 μm, which break apart easily when they hit the ground or when they get disturbed by external factors, such as wind, passing vehicles, or everyday human activity (Horwell & Baxter, 2006). This means that ash that has already settled on the ground can be lifted back into the air and inhaled all over again, making exposure an ongoing cycle even after an eruption has ended. The irregular shape of these particles also makes them more physically damaging once inhaled, as their sharp edges can irritate and damage the lining of the airways (Horwell & Baxter, 2006). Together, these structural properties, combined with how small respirable particles are, make volcanic ash particularly harmful to the respiratory system.

=== 2.3 Chemical and Mineral Composition ===
Volcanic ash is not made up from a single uniform material; its chemical and mineral composition varies depending on the type of magma that erupted and the nature of the eruption. Ash is made up of three main components: glass, which is a quenched (rapidly cooled) melt; lithic fragments, which are pieces of pre-existing rock from the volcanic vent; and crystals, which are minerals that formed within the magma before the eruption (Durant et al., 2010). The crystal component can include minerals such as quartz, feldspar, pyroxenes, amphiboles, and olivine, with the exact proportions depending on the magma composition.

One of the most important and dangerous components of volcanic ash is crystalline silica, which can appear as quartz, cristobalite, or tridymite (Horwell & Baxter, 2006). Cristobalite is considered the most toxic of these forms and is particularly common in volcanoes. It forms through a process called devitrification, the conversion of volcanic glass into crystalline material (Horwell & Baxter, 2006).

Aside from crystalline silica, volcanic ash also carries a range of trace elements and chemical species on its surface (Durant et al., 2010). During an eruption, gases such as fluorine, sulfur dioxide, and hydrogen chloride interact with ash particles, leaving chemical coatings on the surface of the ash (Durant et al., 2010). These surface chemicals can be rapidly released when ash comes into contact with water, contaminating water supplies and soil environments. The presence of iron on ash surfaces is also significant, as it can generate harmful free radicals when it interacts with the lung, potentially causing cell damage even in ash that contains little to no crystalline silica (Horwell & Baxter, 2006).

== Notable Volcanic Eruptions ==

=== 3.1 Mount St. Helens ===
[[File:Vhp img571.jpg|thumb|Mout St. Helens eruption on May 18, 1980, showing the volcanic ash plume produced during the eruption. Source: U.S. Geological Survey (Public Domain).]]
The eruption of Mount St. Helen in Washington, USA, on May 19, 1980, is considered one of the most significant volcanic eruptions in modern history. Following a magnitude 5.1 earthquake, the volcano experienced a lateral blast that destroyed large areas surrounding the mountain. The eruption produced approximately 540 million tons of volcanic ash, which spread across much of the United States and even circled the globe within weeks. The eruption produced a large ash cloud that caused transportation disruptions, environmental damage, and respiratory health concerns (U.S. Geological Survey [USGS], 2023). The event demonstrated how volcanic ash can affect areas far beyond the immediate vicinity of a volcano and remains an important case study for volcanic hazard research.

=== 3.2 Comparison of Major Ash- Producing Eruption ===
Several volcanic eruptions have produced significant amounts of ash, including Mount St. Helens (1980), Mount Pinatubo (1991), and Eyjafjallajökull (2010). While Mount St. Helens caused major regional impacts, Mount Pinatubo had global climate effects due to the large volume of ash and gas released into the atmosphere. In contrast Eyjafjallajökull primarily disrupted air travel across Europe. These eruptions highlight the diverse environmental health and economic impacts that volcanic ash can produce (Newhall & Punongbayan, 1997).

== Effects on Human Health ==

=== 4.1 Respiratory Effects ===
[[File:LungDiagram.jpg|thumb|The human respiratory system, specifically the Alveoli. Source: Canadian Lung Association]]
The respiratory systems are direct targets for volcanic ash due to the ease of inhalation of these tiny particles and their sheer abundance when released. Respirable particles are of greatest concern. These respirable particles, due to their size of around 1/20th the width of a human hair, are capable of being suspended in the air for an extensive amount of time (Shezi et al., 2020). Because of this size, they are fine enough to penetrate deep into the alveolar region of the lungs, where they have the greatest toxic potential (Horwell & Baxter, 2006).

Once these particles reach these alveloar regions, they interact with the cells of the immune system. Resident macrophages and mast cells act as the first line of defense, the primary response, to the inhaled particles. These immune cells are working hard, engulfing these particles, in a process named phagocytosis. The issue is that, when volcanoes release volcanic ash, it does not release only a few particles. The large quantities of ash that are present in the air after an eruption, and the amount of particles inhaled at once, make it difficult for macrophages and mast cells to remove all of them. Due to this, there is a release of cytokines that aim to recruit other immune cells to initiate the second line of defense, but this results in '''something''' inflammation. This inflammatory response that occurs leads to unwanted effects of swelling or irritation in the lungs that causes coughing or shortness of breath (Horwell & Baxter, 2006).

In addition to these respirable particles, exposure to crystalline silica has been studied throughout occupational medicine and has been determined as a cause of silicosis, a serious fibrotic lung disease, and prolonged exposure may also increase the risk of lung cancer (Horwell & Baxter, 2006). This makes the crystalline silica content of ash one of the most critical factors in assessing its health hazard. Repeated exposure to these particles (like seen in people from these volcanic regions that we mentioned above?) can cause chronic respiratory damage.

=== 4.2 Eye and Skin Irritation ===
Volcanic ash also has the ability to impact the eyes and skin. Volcanic ash frequently contains sharp objects that are able to scratch sensitive surfaces when they come into contact. The eyes being exposed to these volcanic ash particles is said to cause unfavourable symptoms like corneal abrasions or scratches, which can cause severe eye pain, conjunctivitis, and more. The skin is also another surface that volcanic ash can attack. When ash comes into contact with the skin, it can cause irritation and reddening of the skin (U.S. Geological Survey).

=== 4.3 Immune Systems ===
The impacts of volcanic ash exposure are noticeable on both the respiratory and eye and skin levels. But the impacts of volcanic ash are able to go beyond and are shown to damage the immune system as a whole. As mentioned before, the primary and secondary responses are how the body is able to fight off bacteria that manage to enter to prevent infections from occurring. What is interesting is that it has been shown that the properties of volcanic ash may play a role in interfering with these systems (Monick et al., 2013).

Macrophages, the first line of defense, play a role in engulfing foreign particles in a process named phagocytosis. Research shows that volcanic ash is actually able to impair macrophages from performing their task, resulting in a reduced ability to remove these foreign particles (Monick et al., 2013). This reduced ability allows for more particles to be present in the body, increasing the chances of infection and other negative effects.

With volcanic ash carrying a range of trace elements like iron, it can actually provide a source of nutrients that bacteria can use to grow and survive inside the body (Monick et al., 2013).

== Effects on Microbial Ecosystem ==

=== 5.1 Soil Microbial Communities ===
[[File:Soilrecovery.jpg|thumb|363x363px|The process by which volcanic ash impacts soil environments over time. Source: Fiantis et al., 2019.]]
Volcanic ash can significantly affect soil microbial communities by altering soil chemistry, pH, moisture retention, and nutrient availability. Immediately after an eruption, a thick layer of ash may reduce microbial activity by covering existing soil and limiting access to oxygen and different organic matter. As a result, the abundance and diversity of microorganisms often decrease in the short term (Fiantis et al., 2019).

However, volcanic ash also contains minerals such as iron, magnesium, potassium, and phosphorus that can gradually improve soil fertility. As weathering occurs, these nutrients are released into the soil and become available to microorganisms. Certain bacteria and fungi are able to colonize newly formed volcanic deposits and play an important role in breaking down minerals, cycling nutrients, and supporting soil development. Over time, microbial communities help create conditions that allow plants and other organisms to establish themselves, contributing to ecosystem recovery (Fiantis et al., 2019).

Volcanic ash can have both positive and negative impacts on soil microbial ecosystems, depending on whether the effects are considered in the short term or the long term.

=== 5.2 Water Contamination ===
Volcanic ash can enter rivers, lakes and ground water through rainfall. Ash particles may increase water turbidity and alter water chemistry, affecting microorganisms that live in aquatic environments. Also, high concentrations of ash can reduce light penetration and sirupt microbial processes that are important for maintaining water quality and ecosystem health (Stewart et al, 2006).

Furthermore, volcanic ash may change the chemical composition of water by releasing minerals and other substances. These changes can alter the balance of microbial communities, causing some species to decline while others become more abundant. As a result normal nutrient cycling and other ecological processes carried out by microorganisms may be disrupted until the ecosystem gradually recovers (Stewart et al., 2006).

=== 5.3 Recovery and Adaptation ===
Although volcanic eruptions can initially disrupt microbial ecosystems, many microorganisms are capable of adapting to the new environmental conditions. Over time, microbial communities recolonize ash- covered areas and contribute to soil formation and nutrient cycling. This recovery process helps establish conditions that support plant growth and the gradual restoration of affected ecosystems (Fiantis et al., 2019).

== Interconnections Between Human Health and Microbial Ecosystem ==
[[File:Volcanic_ash_infographic.jpg|thumb|516x516px|Volcanic ash and its connections infographic. Source: ChatGPT + Raj]]
When volcanic ash is deposited onto soil and water environments, it does not settle as an inert layer. Instead, it restructures the chemical and biological conditions of the microbial communities in that area. Ash alters the carbon and nitrogen concentrations in the soil, changes the pH, and introduces new minerals and trace elements, thereby affecting which microorganisms survive and thrive (Maltz et al., 2024). Various studies were conducted following the 1980 eruption of Mount St. Helens. These studies showed that microbial communities remained fundamentally restructured for decades, with bacterial and fungal composition varying significantly with ashfall intensity and soil chemistry (Maltz et al., 2024). Along with these studies, research on volcanic ash fertilization was also being conducted. These studies showed that once ash concentrations pass a certain threshold, the soil microbiome shifts. Some bacteria that may help plants grow actually increase, while others decline. This suggests ash doesn't just kill off microbial life, it reorganizes it in complex ways (Staudigel et al., 2025). These shifts matter because soil microorganisms are responsible for nearly all biogeochemical transformations, including nutrient cycling, soil formation, and organic matter decomposition, meaning that disruptions to microbial communities have cascading effects on the broader ecosystem (Staudigel et al., 2025).

These environmental changes caused by ashfall do not stay contained in the soil. They also extend into water systems, such as rivers, lakes, and reservoirs, and ultimately reach human homes and human systems. When ash falls into water supplies, it increases acidity and releases soluble contaminants, including fluoride, iron, sulphate, and chloride, into drinking water (Stewart et al., 2006). It also increases turbidity, which is dangerous because the ash particles present interfere with the disinfection process, allowing harmful bacteria to survive in the water (Stewart et al., 2006). This raises the risk of waterborne disease outbreaks (Stewart et al., 2006). Aside from water contamination, the restructuring of soil microbial communities also affects food systems. Changes in soil chemistry disrupt nutrient cycling, which reduces soil fertility and can lower crop yields. On top of this, volcanic air pollution has been linked to respiratory illness, cardiovascular effects, and increased healthcare visits in exposed populations (Stewart et al., 2022). This shows that the path from environmental disruption to human health outcomes works through several pathways at once, not just one (Stewart et al., 2022). Together, these interconnections show that the health impacts of volcanic ash cannot be understood by looking at geology, microbiology, or human health on their own; they are fundamentally linked.
== Conclusions ==
Understanding volcanic ash requires integrating geology, microbiology, and statistics, as each discipline provides insights into how eruptions affect ecosystems and human health. This project demonstrated that volcanic eruptions extend far beyond a single geological area; their impacts travel through surrounding ecosystems and human populations in ways that can only be fully understood through an integrated approach.

Volcanic ash composition, shaped by magma type and eruption style, determines how hazardous it is. Fine particles and crystalline silica content are contributors to acute respiratory effects and long-term disease risk. However, ash does not harm humans alone. Once deposited in soil and water, it restructures entire microbial communities and alters pH levels, altering the balance of bacteria and fungi that support ecosystem recovery. These changes stay in the ecosystem and persist for decades, as shown by Mount St. Helens. Understanding these effects requires quantitative methods: statistical analysis of data, probabilistic risk assessment models, and grain-size characterization across eruptions translate geological hazards into public health predictions. It also requires a deep understanding of microbial systems and how the exposure affects them.

==References==
<references />
Baxter, P. J., Ing, R., Falk, H., & Plikaytis, B. (1983). Mount St. Helens eruptions: The acute respiratory effects of volcanic ash in a North American community. Archives of Environmental Health, 38(3), 138–143. https://doi.org/10.1080/00039896.1983.10543892

Durant, A. J., Bonadonna, C., & Horwell, C. J. (2010). Atmospheric and Environmental Impacts of Volcanic Particulates. Elements, 6(4), 235–240. https://doi.org/10.2113/gselements.6.4.235

Fiantis, D., Ginting, F. I., Gusnidar, G., Nelson, M., & Van Ranst, E. (2019). ''Volcanic ash, soil formation, and ecosystem development.''

Horwell, C. J., & Baxter, P. J. (2006). The respiratory health hazards of volcanic ash: a review for volcanic risk mitigation. Bulletin of Volcanology, 69(1), 1–24. https://doi.org/10.1007/s00445-006-0052-y

Newhall, C. G., & Punongbayan, R. S. (1997). ''The cataclysmic 1991 eruption of Mount Pinatubo, Philippines''. U.S. Geological Survey Fact Sheet 113-97.

Maltz, M.R., Allen, M.F., Phillips, M.L., Hernandez, R.R., Shulman, H.B., Freund, L., Andrews, L.V., Botthoff, J.K., and Aronson, E.L. (2024). Microbial community structure in recovering forests of Mount St. Helens. Frontiers in Microbiomes, 3, 1399416. https://doi.org/10.3389/frmbi.2024.1399416

Monick, M. M., Baltrusaitis, J., Powers, L. S., Borcherding, J. A., Caraballo, J. C., Mudunkotuwa, I., Peate, D. W., Walters, K., Thompson, J. M., Grassian, V. H., Gudmundsson, G., & Comellas, A. P. (2013). Effects of Eyjafjallajökull Volcanic Ash on Innate Immune System Responses and Bacterial Growth in Vitro. ''Environmental Health Perspectives'', ''121''(6), 691–698. https://doi.org/10.1289/ehp.1206004.

Shezi, B., Mathee, A., Cele, N., Ndabandaba, S., & Street, R. A. (2020). Occupational Exposure to Fine Particulate Matter (PM4 and PM2.5) during Hand-Made Cookware Operation: Personal, Indoor and Outdoor Levels. International journal of environmental research and public health, 17(20), 7522. <nowiki>https://doi.org/10.3390/ijerph17207522</nowiki>

Stewart, C., Johnston, D. M., Leonard, G. S., Horwell, C. J., Thordarson, T., & Cronin, S. J. (2006). ''Contamination of water supplies by volcanic ashfall: A literature review and simple impact modelling.''

U.S. Geological Survey. (n.d.). ''Volcanic ash impacts & mitigation: Eyes and skin''. U.S. Department of the Interior. <nowiki>https://volcanoes.usgs.gov/volcanic_ash/eye_skin.html</nowiki>

U.S. Geological Survey. (2023). ''1980 Cataclysmic Eruption''. Retrieved from <nowiki>https://www.usgs.gov/volcanoes/mount-st.-helens/science/1980-cataclysmic-eruption</nowiki>

Canadian Lung Association. ''Your lungs'' [Image]. Canadian Lung Association. <nowiki>https://www.lung.ca/how-to-protect-your-lungs/your-lungs/</nowiki>

U.S. Geological Survey. (2017, December 13). ''Illustration of the basic process of magma formation, movement to the surface, and eruption through a volcanic vent'' [Illustration]. <nowiki>https://www.usgs.gov/media/images/illustration-basic-process-magma-formation-movement-s</nowiki>

U.S. Geological Survey. (2015, November 13). ''Scanning electron microscope image of volcanic ash'' [Photograph]. <nowiki>https://www.usgs.gov/media/images/scanning-electron-microscope-image-volcanic-ash</nowiki>

Fiantis, D., Ginting, F. I., Gusnidar, Nelson, M., & Minasny, B. (2019). ''Volcanic ash, insecurity for the people but securing fertile soil for the future''. ''Sustainability, 11''(11), 3072. <nowiki>https://doi.org/10.3390/su11113072</nowiki>

‌

‌{{Projectbox_EOSC311}}
[[Category:EOSC311]]

Course:EOSC311/2026/Volcanic Ash Composition and its effects on Human Health and Microbial Ecosystems

2026-06-18T03:29:48Z

RAJMEHRA: /* Interconnections Between Human Health and Microbial Ecosystem */

== Introduction ==
Volcanic eruptions are mighty natural forces that are able to cause vast changes in ecosystems and the atmosphere. Volcanoes, when they erupt, release large amounts of volcanic ash, volcanic gases, and fragments of rocks that are able to be spread over long distances through many mediums like wind and water, affecting not only local but also global scales. Most of the time, volcanoes are talked about from a geological perspective, but the impacts of volcanoes go beyond simple things like land creation. Volcanic emissions can have an influence on air, water, and soil quality that can have an impact on both human health and the microbial ecosystem. This project looks at the connections between volcanic geology, human health and microbiology by exploring how volcanic ash materials have an impact on respiratory and immune systems, as well as microbial ecosystems.

==Volcanic Ash Composition==

=== 2.1 Formation of Volcanic Ash ===
[[File:VolcanoImage.jpg|thumb|The process by which volcanic ash forms, starting from magma ascending from the mantle to the surface of the Earth. Source: U.S. Geological Survey (Public Domain).]]
Magma is molten rock found beneath the Earth's surface that contains dissolved gases, including water vapor, carbon dioxide (CO₂), and sulfur dioxide (SO₂). As magma rises toward the surface, pressure decreases, causing these gases to escape and form bubbles known as vesicles, similar to how a carbonated drink fizzes when opened. When magma rises quickly, pressure builds up inside these bubbles until they burst, breaking the magma into fine particles known as volcanic ash (Durant et al., 2010). The composition of the magma affects how explosive the eruption is — magmas with high silica content tend to erupt more explosively, producing larger amounts of ash.
=== 2.2 Particle Size and Structure ===
During an explosive volcanic eruption, rocks, mineral fragments, and/or ash are ejected into the air; these are known as pyroclasts. [[File:Respirable Material Content in Volcanic Ash from Major Eruptions.jpg|thumb|400px|Table 1. Respirable material (<4 μm) content in ash from nine historical eruptions. Adapted from Horwell & Baxter (2006).]] Volcanic ash is defined as pyroclasts with a diameter of 2mm or less, an important factor in determining how hazardous the ash is to human health. The size is measured using aerodynamic diameter, and particles are classified into two key health-relevant categories: thoracic particles (PM10), which are less than 10 μm in diameter, and respirable particles (PM4), which are less than 4 μm in diameter (Horwell & Baxter, 2006). The percentage of respirable material in ash varies considerably depending on the volcano, the explosivity of the eruption, and the distance from the vent at which ash is collected (Horwell & Baxter, 2006).
[[File:VolcanicAsh.jpg|thumb|The shape and size of volcanic ash under a microscope with a 50 micrometre scale bar. Source: U.S. Geological Survey (Public Domain).]]
As shown in Table 1, the proportion of respirable material varies across eruptions, with no clear relationship to the Volcanic Explosivity Index (VEI). For example, Pinatubo's 1991 eruption had the highest VEI of the group (6) but a comparatively low respirable fraction (9.8%), while Mount St. Helens and Vesuvius, both with a VEI of 5, produced different proportions (11.7% and 16.9%, respectively). This suggests that the explosivity of an eruption alone does not determine how hazardous its ash will be to human health; other factors, such as magma composition and fragmentation style, likely play a larger role in generating fine, respirable particles.

Fine ash particles tend to fall in loose clusters of less than 100 μm, which break apart easily when they hit the ground or when they get disturbed by external factors, such as wind, passing vehicles, or everyday human activity (Horwell & Baxter, 2006). This means that ash that has already settled on the ground can be lifted back into the air and inhaled all over again, making exposure an ongoing cycle even after an eruption has ended. The irregular shape of these particles also makes them more physically damaging once inhaled, as their sharp edges can irritate and damage the lining of the airways (Horwell & Baxter, 2006). Together, these structural properties, combined with how small respirable particles are, make volcanic ash particularly harmful to the respiratory system.

=== 2.3 Chemical and Mineral Composition ===
Volcanic ash is not made up from a single uniform material; its chemical and mineral composition varies depending on the type of magma that erupted and the nature of the eruption. Ash is made up of three main components: glass, which is a quenched (rapidly cooled) melt; lithic fragments, which are pieces of pre-existing rock from the volcanic vent; and crystals, which are minerals that formed within the magma before the eruption (Durant et al., 2010). The crystal component can include minerals such as quartz, feldspar, pyroxenes, amphiboles, and olivine, with the exact proportions depending on the magma composition.

One of the most important and dangerous components of volcanic ash is crystalline silica, which can appear as quartz, cristobalite, or tridymite (Horwell & Baxter, 2006). Cristobalite is considered the most toxic of these forms and is particularly common in volcanoes. It forms through a process called devitrification, the conversion of volcanic glass into crystalline material (Horwell & Baxter, 2006).

Aside from crystalline silica, volcanic ash also carries a range of trace elements and chemical species on its surface (Durant et al., 2010). During an eruption, gases such as fluorine, sulfur dioxide, and hydrogen chloride interact with ash particles, leaving chemical coatings on the surface of the ash (Durant et al., 2010). These surface chemicals can be rapidly released when ash comes into contact with water, contaminating water supplies and soil environments. The presence of iron on ash surfaces is also significant, as it can generate harmful free radicals when it interacts with the lung, potentially causing cell damage even in ash that contains little to no crystalline silica (Horwell & Baxter, 2006).

== Notable Volcanic Eruptions ==

=== 3.1 Mount St. Helens ===
[[File:Vhp img571.jpg|thumb|Mout St. Helens eruption on May 18, 1980, showing the volcanic ash plume produced during the eruption. Source: U.S. Geological Survey (Public Domain).]]
The eruption of Mount St. Helen in Washington, USA, on May 19, 1980, is considered one of the most significant volcanic eruptions in modern history. Following a magnitude 5.1 earthquake, the volcano experienced a lateral blast that destroyed large areas surrounding the mountain. The eruption produced approximately 540 million tons of volcanic ash, which spread across much of the United States and even circled the globe within weeks. The eruption produced a large ash cloud that caused transportation disruptions, environmental damage, and respiratory health concerns (U.S. Geological Survey [USGS], 2023). The event demonstrated how volcanic ash can affect areas far beyond the immediate vicinity of a volcano and remains an important case study for volcanic hazard research.

=== 3.2 Comparison of Major Ash- Producing Eruption ===
Several volcanic eruptions have produced significant amounts of ash, including Mount St. Helens (1980), Mount Pinatubo (1991), and Eyjafjallajökull (2010). While Mount St. Helens caused major regional impacts, Mount Pinatubo had global climate effects due to the large volume of ash and gas released into the atmosphere. In contrast Eyjafjallajökull primarily disrupted air travel across Europe. These eruptions highlight the diverse environmental health and economic impacts that volcanic ash can produce (Newhall & Punongbayan, 1997).

== Effects on Human Health ==

=== 4.1 Respiratory Effects ===
[[File:LungDiagram.jpg|thumb|The human respiratory system, specifically the Alveoli. Source: Canadian Lung Association]]
The respiratory systems are direct targets for volcanic ash due to the ease of inhalation of these tiny particles and their sheer abundance when released. Respirable particles are of greatest concern. These respirable particles, due to their size of around 1/20th the width of a human hair, are capable of being suspended in the air for an extensive amount of time (Shezi et al., 2020). Because of this size, they are fine enough to penetrate deep into the alveolar region of the lungs, where they have the greatest toxic potential (Horwell & Baxter, 2006).

Once these particles reach these alveloar regions, they interact with the cells of the immune system. Resident macrophages and mast cells act as the first line of defense, the primary response, to the inhaled particles. These immune cells are working hard, engulfing these particles, in a process named phagocytosis. The issue is that, when volcanoes release volcanic ash, it does not release only a few particles. The large quantities of ash that are present in the air after an eruption, and the amount of particles inhaled at once, make it difficult for macrophages and mast cells to remove all of them. Due to this, there is a release of cytokines that aim to recruit other immune cells to initiate the second line of defense, but this results in '''something''' inflammation. This inflammatory response that occurs leads to unwanted effects of swelling or irritation in the lungs that causes coughing or shortness of breath (Horwell & Baxter, 2006).

In addition to these respirable particles, exposure to crystalline silica has been studied throughout occupational medicine and has been determined as a cause of silicosis, a serious fibrotic lung disease, and prolonged exposure may also increase the risk of lung cancer (Horwell & Baxter, 2006). This makes the crystalline silica content of ash one of the most critical factors in assessing its health hazard. Repeated exposure to these particles (like seen in people from these volcanic regions that we mentioned above?) can cause chronic respiratory damage.

=== 4.2 Eye and Skin Irritation ===
Volcanic ash also has the ability to impact the eyes and skin. Volcanic ash frequently contains sharp objects that are able to scratch sensitive surfaces when they come into contact. The eyes being exposed to these volcanic ash particles is said to cause unfavourable symptoms like corneal abrasions or scratches, which can cause severe eye pain, conjunctivitis, and more. The skin is also another surface that volcanic ash can attack. When ash comes into contact with the skin, it can cause irritation and reddening of the skin (U.S. Geological Survey).

=== 4.3 Immune Systems ===
The impacts of volcanic ash exposure are noticeable on both the respiratory and eye and skin levels. But the impacts of volcanic ash are able to go beyond and are shown to damage the immune system as a whole. As mentioned before, the primary and secondary responses are how the body is able to fight off bacteria that manage to enter to prevent infections from occurring. What is interesting is that it has been shown that the properties of volcanic ash may play a role in interfering with these systems (Monick et al., 2013).

Macrophages, the first line of defense, play a role in engulfing foreign particles in a process named phagocytosis. Research shows that volcanic ash is actually able to impair macrophages from performing their task, resulting in a reduced ability to remove these foreign particles (Monick et al., 2013). This reduced ability allows for more particles to be present in the body, increasing the chances of infection and other negative effects.

With volcanic ash carrying a range of trace elements like iron, it can actually provide a source of nutrients that bacteria can use to grow and survive inside the body (Monick et al., 2013).

== Effects on Microbial Ecosystem ==

=== 5.1 Soil Microbial Communities ===
[[File:Soilrecovery.jpg|thumb|363x363px|The process by which volcanic ash impacts soil environments over time. Source: (Fiantis et al., 2019).]]
Volcanic ash can significantly affect soil microbial communities by altering soil chemistry, pH, moisture retention, and nutrient availability. Immediately after an eruption, a thick layer of ash may reduce microbial activity by covering existing soil and limiting access to oxygen and different organic matter. As a result, the abundance and diversity of microorganisms often decrease in the short term (Fiantis et al., 2019).

However, volcanic ash also contains minerals such as iron, magnesium, potassium, and phosphorus that can gradually improve soil fertility. As weathering occurs, these nutrients are released into the soil and become available to microorganisms. Certain bacteria and fungi are able to colonize newly formed volcanic deposits and play an important role in breaking down minerals, cycling nutrients, and supporting soil development. Over time, microbial communities help create conditions that allow plants and other organisms to establish themselves, contributing to ecosystem recovery (Fiantis et al., 2019).

Volcanic ash can have both positive and negative impacts on soil microbial ecosystems, depending on whether the effects are considered in the short term or the long term.

=== 5.2 Water Contamination ===
Volcanic ash can enter rivers, lakes and ground water through rainfall. Ash particles may increase water turbidity and alter water chemistry, affecting microorganisms that live in aquatic environments. Also, high concentrations of ash can reduce light penetration and sirupt microbial processes that are important for maintaining water quality and ecosystem health (Stewart et al, 2006).

Furthermore, volcanic ash may change the chemical composition of water by releasing minerals and other substances. These changes can alter the balance of microbial communities, causing some species to decline while others become more abundant. As a result normal nutrient cycling and other ecological processes carried out by microorganisms may be disrupted until the ecosystem gradually recovers (Stewart et al., 2006).

=== 5.3 Recovery and Adaptation ===
Although volcanic eruptions can initially disrupt microbial ecosystems, many microorganisms are capable of adapting to the new environmental conditions. Over time, microbial communities recolonize ash- covered areas and contribute to soil formation and nutrient cycling. This recovery process helps establish conditions that support plant growth and the gradual restoration of affected ecosystems (Fiantis et al., 2019).

== Interconnections Between Human Health and Microbial Ecosystem ==
[[File:Volcanic_ash_infographic.jpg|thumb|516x516px|Volcanic ash and its connections infographic. Source: ChatGPT + Raj]]
When volcanic ash is deposited onto soil and water environments, it does not settle as an inert layer. Instead, it restructures the chemical and biological conditions of the microbial communities in that area. Ash alters the carbon and nitrogen concentrations in the soil, changes the pH, and introduces new minerals and trace elements, thereby affecting which microorganisms survive and thrive (Maltz et al., 2024). Various studies were conducted following the 1980 eruption of Mount St. Helens. These studies showed that microbial communities remained fundamentally restructured for decades, with bacterial and fungal composition varying significantly with ashfall intensity and soil chemistry (Maltz et al., 2024). Along with these studies, research on volcanic ash fertilization was also being conducted. These studies showed that once ash concentrations pass a certain threshold, the soil microbiome shifts. Some bacteria that may help plants grow actually increase, while others decline. This suggests ash doesn't just kill off microbial life, it reorganizes it in complex ways (Staudigel et al., 2025). These shifts matter because soil microorganisms are responsible for nearly all biogeochemical transformations, including nutrient cycling, soil formation, and organic matter decomposition, meaning that disruptions to microbial communities have cascading effects on the broader ecosystem (Staudigel et al., 2025).

These environmental changes caused by ashfall do not stay contained in the soil. They also extend into water systems, such as rivers, lakes, and reservoirs, and ultimately reach human homes and human systems. When ash falls into water supplies, it increases acidity and releases soluble contaminants, including fluoride, iron, sulphate, and chloride, into drinking water (Stewart et al., 2006). It also increases turbidity, which is dangerous because the ash particles present interfere with the disinfection process, allowing harmful bacteria to survive in the water (Stewart et al., 2006). This raises the risk of waterborne disease outbreaks (Stewart et al., 2006). Aside from water contamination, the restructuring of soil microbial communities also affects food systems. Changes in soil chemistry disrupt nutrient cycling, which reduces soil fertility and can lower crop yields. On top of this, volcanic air pollution has been linked to respiratory illness, cardiovascular effects, and increased healthcare visits in exposed populations (Stewart et al., 2022). This shows that the path from environmental disruption to human health outcomes works through several pathways at once, not just one (Stewart et al., 2022). Together, these interconnections show that the health impacts of volcanic ash cannot be understood by looking at geology, microbiology, or human health on their own; they are fundamentally linked.
== Conclusions ==
Understanding volcanic ash requires integrating geology, microbiology, and statistics, as each discipline provides insights into how eruptions affect ecosystems and human health. This project demonstrated that volcanic eruptions extend far beyond a single geological area; their impacts travel through surrounding ecosystems and human populations in ways that can only be fully understood through an integrated approach.

==References==
<references />
Baxter, P. J., Ing, R., Falk, H., & Plikaytis, B. (1983). Mount St. Helens eruptions: The acute respiratory effects of volcanic ash in a North American community. Archives of Environmental Health, 38(3), 138–143. https://doi.org/10.1080/00039896.1983.10543892

Durant, A. J., Bonadonna, C., & Horwell, C. J. (2010). Atmospheric and Environmental Impacts of Volcanic Particulates. Elements, 6(4), 235–240. https://doi.org/10.2113/gselements.6.4.235

Fiantis, D., Ginting, F. I., Gusnidar, G., Nelson, M., & Van Ranst, E. (2019). ''Volcanic ash, soil formation, and ecosystem development.''

Horwell, C. J., & Baxter, P. J. (2006). The respiratory health hazards of volcanic ash: a review for volcanic risk mitigation. Bulletin of Volcanology, 69(1), 1–24. https://doi.org/10.1007/s00445-006-0052-y

Newhall, C. G., & Punongbayan, R. S. (1997). ''The cataclysmic 1991 eruption of Mount Pinatubo, Philippines''. U.S. Geological Survey Fact Sheet 113-97.

Maltz, M.R., Allen, M.F., Phillips, M.L., Hernandez, R.R., Shulman, H.B., Freund, L., Andrews, L.V., Botthoff, J.K., and Aronson, E.L. (2024). Microbial community structure in recovering forests of Mount St. Helens. Frontiers in Microbiomes, 3, 1399416. https://doi.org/10.3389/frmbi.2024.1399416

Monick, M. M., Baltrusaitis, J., Powers, L. S., Borcherding, J. A., Caraballo, J. C., Mudunkotuwa, I., Peate, D. W., Walters, K., Thompson, J. M., Grassian, V. H., Gudmundsson, G., & Comellas, A. P. (2013). Effects of Eyjafjallajökull Volcanic Ash on Innate Immune System Responses and Bacterial Growth in Vitro. ''Environmental Health Perspectives'', ''121''(6), 691–698. https://doi.org/10.1289/ehp.1206004.

Shezi, B., Mathee, A., Cele, N., Ndabandaba, S., & Street, R. A. (2020). Occupational Exposure to Fine Particulate Matter (PM4 and PM2.5) during Hand-Made Cookware Operation: Personal, Indoor and Outdoor Levels. International journal of environmental research and public health, 17(20), 7522. <nowiki>https://doi.org/10.3390/ijerph17207522</nowiki>

Stewart, C., Johnston, D. M., Leonard, G. S., Horwell, C. J., Thordarson, T., & Cronin, S. J. (2006). ''Contamination of water supplies by volcanic ashfall: A literature review and simple impact modelling.''

U.S. Geological Survey. (n.d.). ''Volcanic ash impacts & mitigation: Eyes and skin''. U.S. Department of the Interior. <nowiki>https://volcanoes.usgs.gov/volcanic_ash/eye_skin.html</nowiki>

U.S. Geological Survey. (2023). ''1980 Cataclysmic Eruption''. Retrieved from <nowiki>https://www.usgs.gov/volcanoes/mount-st.-helens/science/1980-cataclysmic-eruption</nowiki>

Canadian Lung Association. ''Your lungs'' [Image]. Canadian Lung Association. <nowiki>https://www.lung.ca/how-to-protect-your-lungs/your-lungs/</nowiki>

U.S. Geological Survey. (2017, December 13). ''Illustration of the basic process of magma formation, movement to the surface, and eruption through a volcanic vent'' [Illustration]. <nowiki>https://www.usgs.gov/media/images/illustration-basic-process-magma-formation-movement-s</nowiki>

U.S. Geological Survey. (2015, November 13). ''Scanning electron microscope image of volcanic ash'' [Photograph]. <nowiki>https://www.usgs.gov/media/images/scanning-electron-microscope-image-volcanic-ash</nowiki>

Fiantis, D., Ginting, F. I., Gusnidar, Nelson, M., & Minasny, B. (2019). ''Volcanic ash, insecurity for the people but securing fertile soil for the future''. ''Sustainability, 11''(11), 3072. <nowiki>https://doi.org/10.3390/su11113072</nowiki>

‌

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[[Category:EOSC311]]

File:Volcanic ash infographic.jpg

2026-06-18T03:29:05Z

RAJMEHRA: Uploaded own work with UploadWizard

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Course:EOSC311/2026/Volcanic Ash Composition and its effects on Human Health and Microbial Ecosystems

2026-06-18T03:12:34Z

RAJMEHRA: image

== Introduction ==
Volcanic eruptions are mighty natural forces that are able to cause vast changes in ecosystems and the atmosphere. Volcanoes, when they erupt, release large amounts of volcanic ash, volcanic gases, and fragments of rocks that are able to be spread over long distances through many mediums like wind and water, affecting not only local but also global scales. Most of the time, volcanoes are talked about from a geological perspective, but the impacts of volcanoes go beyond simple things like land creation. Volcanic emissions can have an influence on air, water, and soil quality that can have an impact on both human health and the microbial ecosystem. This project looks at the connections between volcanic geology, human health and microbiology by exploring how volcanic ash materials have an impact on respiratory and immune systems, as well as microbial ecosystems.

==Volcanic Ash Composition==

=== 2.1 Formation of Volcanic Ash ===
[[File:VolcanoImage.jpg|thumb|The process by which volcanic ash forms, starting from magma ascending from the mantle to the surface of the Earth. Source: U.S. Geological Survey (Public Domain).]]
Magma is molten rock found beneath the Earth's surface that contains dissolved gases, including water vapor, carbon dioxide (CO₂), and sulfur dioxide (SO₂). As magma rises toward the surface, pressure decreases, causing these gases to escape and form bubbles known as vesicles, similar to how a carbonated drink fizzes when opened. When magma rises quickly, pressure builds up inside these bubbles until they burst, breaking the magma into fine particles known as volcanic ash (Durant et al., 2010). The composition of the magma affects how explosive the eruption is — magmas with high silica content tend to erupt more explosively, producing larger amounts of ash.
=== 2.2 Particle Size and Structure ===
During an explosive volcanic eruption, rocks, mineral fragments, and/or ash are ejected into the air; these are known as pyroclasts. [[File:Respirable Material Content in Volcanic Ash from Major Eruptions.jpg|thumb|400px|Table 1. Respirable material (<4 μm) content in ash from nine historical eruptions. Adapted from Horwell & Baxter (2006).]] Volcanic ash is defined as pyroclasts with a diameter of 2mm or less, an important factor in determining how hazardous the ash is to human health. The size is measured using aerodynamic diameter, and particles are classified into two key health-relevant categories: thoracic particles (PM10), which are less than 10 μm in diameter, and respirable particles (PM4), which are less than 4 μm in diameter (Horwell & Baxter, 2006). The percentage of respirable material in ash varies considerably depending on the volcano, the explosivity of the eruption, and the distance from the vent at which ash is collected (Horwell & Baxter, 2006).
[[File:VolcanicAsh.jpg|thumb|The shape and size of volcanic ash under a microscope with a 50 micrometre scale bar. Source: U.S. Geological Survey (Public Domain).]]
As shown in Table 1, the proportion of respirable material varies across eruptions, with no clear relationship to the Volcanic Explosivity Index (VEI). For example, Pinatubo's 1991 eruption had the highest VEI of the group (6) but a comparatively low respirable fraction (9.8%), while Mount St. Helens and Vesuvius, both with a VEI of 5, produced different proportions (11.7% and 16.9%, respectively). This suggests that the explosivity of an eruption alone does not determine how hazardous its ash will be to human health; other factors, such as magma composition and fragmentation style, likely play a larger role in generating fine, respirable particles.

Fine ash particles tend to fall in loose clusters of less than 100 μm, which break apart easily when they hit the ground or when they get disturbed by external factors, such as wind, passing vehicles, or everyday human activity (Horwell & Baxter, 2006). This means that ash that has already settled on the ground can be lifted back into the air and inhaled all over again, making exposure an ongoing cycle even after an eruption has ended. The irregular shape of these particles also makes them more physically damaging once inhaled, as their sharp edges can irritate and damage the lining of the airways (Horwell & Baxter, 2006). Together, these structural properties, combined with how small respirable particles are, make volcanic ash particularly harmful to the respiratory system.

=== 2.3 Chemical and Mineral Composition ===
Volcanic ash is not made up from a single uniform material; its chemical and mineral composition varies depending on the type of magma that erupted and the nature of the eruption. Ash is made up of three main components: glass, which is a quenched (rapidly cooled) melt; lithic fragments, which are pieces of pre-existing rock from the volcanic vent; and crystals, which are minerals that formed within the magma before the eruption (Durant et al., 2010). The crystal component can include minerals such as quartz, feldspar, pyroxenes, amphiboles, and olivine, with the exact proportions depending on the magma composition.

One of the most important and dangerous components of volcanic ash is crystalline silica, which can appear as quartz, cristobalite, or tridymite (Horwell & Baxter, 2006). Cristobalite is considered the most toxic of these forms and is particularly common in volcanoes. It forms through a process called devitrification, the conversion of volcanic glass into crystalline material (Horwell & Baxter, 2006).

Aside from crystalline silica, volcanic ash also carries a range of trace elements and chemical species on its surface (Durant et al., 2010). During an eruption, gases such as fluorine, sulfur dioxide, and hydrogen chloride interact with ash particles, leaving chemical coatings on the surface of the ash (Durant et al., 2010). These surface chemicals can be rapidly released when ash comes into contact with water, contaminating water supplies and soil environments. The presence of iron on ash surfaces is also significant, as it can generate harmful free radicals when it interacts with the lung, potentially causing cell damage even in ash that contains little to no crystalline silica (Horwell & Baxter, 2006).

== Notable Volcanic Eruptions ==

=== 3.1 Mount St. Helens ===
[[File:Vhp img571.jpg|thumb|Mout St. Helens eruption on May 18, 1980, showing the volcanic ash plume produced during the eruption. Source: U.S. Geological Survey (Public Domain).]]
The eruption of Mount St. Helen in Washington, USA, on May 19, 1980, is considered one of the most significant volcanic eruptions in modern history. Following a magnitude 5.1 earthquake, the volcano experienced a lateral blast that destroyed large areas surrounding the mountain. The eruption produced approximately 540 million tons of volcanic ash, which spread across much of the United States and even circled the globe within weeks. The eruption produced a large ash cloud that caused transportation disruptions, environmental damage, and respiratory health concerns (U.S. Geological Survey [USGS], 2023). The event demonstrated how volcanic ash can affect areas far beyond the immediate vicinity of a volcano and remains an important case study for volcanic hazard research.

=== 3.2 Comparison of Major Ash- Producing Eruption ===
Several volcanic eruptions have produced significant amounts of ash, including Mount St. Helens (1980), Mount Pinatubo (1991), and Eyjafjallajökull (2010). While Mount St. Helens caused major regional impacts, Mount Pinatubo had global climate effects due to the large volume of ash and gas released into the atmosphere. In contrast Eyjafjallajökull primarily disrupted air travel across Europe. These eruptions highlight the diverse environmental health and economic impacts that volcanic ash can produce (Newhall & Punongbayan, 1997).

== Effects on Human Health ==

=== 4.1 Respiratory Effects ===
[[File:LungDiagram.jpg|thumb|The human respiratory system, specifically the Alveoli. Source: Canadian Lung Association]]
The respiratory systems are direct targets for volcanic ash due to the ease of inhalation of these tiny particles and their sheer abundance when released. Respirable particles are of greatest concern. These respirable particles, due to their size of around 1/20th the width of a human hair, are capable of being suspended in the air for an extensive amount of time (Shezi et al., 2020). Because of this size, they are fine enough to penetrate deep into the alveolar region of the lungs, where they have the greatest toxic potential (Horwell & Baxter, 2006).

Once these particles reach these alveloar regions, they interact with the cells of the immune system. Resident macrophages and mast cells act as the first line of defense, the primary response, to the inhaled particles. These immune cells are working hard, engulfing these particles, in a process named phagocytosis. The issue is that, when volcanoes release volcanic ash, it does not release only a few particles. The large quantities of ash that are present in the air after an eruption, and the amount of particles inhaled at once, make it difficult for macrophages and mast cells to remove all of them. Due to this, there is a release of cytokines that aim to recruit other immune cells to initiate the second line of defense, but this results in '''something''' inflammation. This inflammatory response that occurs leads to unwanted effects of swelling or irritation in the lungs that causes coughing or shortness of breath (Horwell & Baxter, 2006).

In addition to these respirable particles, exposure to crystalline silica has been studied throughout occupational medicine and has been determined as a cause of silicosis, a serious fibrotic lung disease, and prolonged exposure may also increase the risk of lung cancer (Horwell & Baxter, 2006). This makes the crystalline silica content of ash one of the most critical factors in assessing its health hazard. Repeated exposure to these particles (like seen in people from these volcanic regions that we mentioned above?) can cause chronic respiratory damage.

=== 4.2 Eye and Skin Irritation ===
Volcanic ash also has the ability to impact the eyes and skin. Volcanic ash frequently contains sharp objects that are able to scratch sensitive surfaces when they come into contact. The eyes being exposed to these volcanic ash particles is said to cause unfavourable symptoms like corneal abrasions or scratches, which can cause severe eye pain, conjunctivitis, and more. The skin is also another surface that volcanic ash can attack. When ash comes into contact with the skin, it can cause irritation and reddening of the skin (U.S. Geological Survey).

=== 4.3 Immune Systems ===
The impacts of volcanic ash exposure are noticeable on both the respiratory and eye and skin levels. But the impacts of volcanic ash are able to go beyond and are shown to damage the immune system as a whole. As mentioned before, the primary and secondary responses are how the body is able to fight off bacteria that manage to enter to prevent infections from occurring. What is interesting is that it has been shown that the properties of volcanic ash may play a role in interfering with these systems (Monick et al., 2013).

Macrophages, the first line of defense, play a role in engulfing foreign particles in a process named phagocytosis. Research shows that volcanic ash is actually able to impair macrophages from performing their task, resulting in a reduced ability to remove these foreign particles (Monick et al., 2013). This reduced ability allows for more particles to be present in the body, increasing the chances of infection and other negative effects.

With volcanic ash carrying a range of trace elements like iron, it can actually provide a source of nutrients that bacteria can use to grow and survive inside the body (Monick et al., 2013).

== Effects on Microbial Ecosystem ==

=== 5.1 Soil Microbial Communities ===
[[File:Soilrecovery.jpg|thumb|363x363px|The process by which volcanic ash impacts soil environments over time. Source: (Fiantis et al., 2019).]]
Volcanic ash can significantly affect soil microbial communities by altering soil chemistry, pH, moisture retention, and nutrient availability. Immediately after an eruption, a thick layer of ash may reduce microbial activity by covering existing soil and limiting access to oxygen and different organic matter. As a result, the abundance and diversity of microorganisms often decrease in the short term (Fiantis et al., 2019).

However, volcanic ash also contains minerals such as iron, magnesium, potassium, and phosphorus that can gradually improve soil fertility. As weathering occurs, these nutrients are released into the soil and become available to microorganisms. Certain bacteria and fungi are able to colonize newly formed volcanic deposits and play an important role in breaking down minerals, cycling nutrients, and supporting soil development. Over time, microbial communities help create conditions that allow plants and other organisms to establish themselves, contributing to ecosystem recovery (Fiantis et al., 2019).

Volcanic ash can have both positive and negative impacts on soil microbial ecosystems, depending on whether the effects are considered in the short term or the long term.

=== 5.2 Water Contamination ===
Volcanic ash can enter rivers, lakes and ground water through rainfall. Ash particles may increase water turbidity and alter water chemistry, affecting microorganisms that live in aquatic environments. Also, high concentrations of ash can reduce light penetration and sirupt microbial processes that are important for maintaining water quality and ecosystem health (Stewart et al, 2006).

Furthermore, volcanic ash may change the chemical composition of water by releasing minerals and other substances. These changes can alter the balance of microbial communities, causing some species to decline while others become more abundant. As a result normal nutrient cycling and other ecological processes carried out by microorganisms may be disrupted until the ecosystem gradually recovers (Stewart et al., 2006).

=== 5.3 Recovery and Adaptation ===
Although volcanic eruptions can initially disrupt microbial ecosystems, many microorganisms are capable of adapting to the new environmental conditions. Over time, microbial communities recolonize ash- covered areas and contribute to soil formation and nutrient cycling. This recovery process helps establish conditions that support plant growth and the gradual restoration of affected ecosystems (Fiantis et al., 2019).

== Interconnections Between Human Health and Microbial Ecosystem ==

When volcanic ash is deposited onto soil and water environments, it does not settle as an inert layer. Instead, it restructures the chemical and biological conditions of the microbial communities in that area. Ash alters the carbon and nitrogen concentrations in the soil, changes the pH, and introduces new minerals and trace elements, thereby affecting which microorganisms survive and thrive (Maltz et al., 2024). Various studies were conducted following the 1980 eruption of Mount St. Helens. These studies showed that microbial communities remained fundamentally restructured for decades, with bacterial and fungal composition varying significantly with ashfall intensity and soil chemistry (Maltz et al., 2024). Along with these studies, research on volcanic ash fertilization was also being conducted. These studies showed that once ash concentrations pass a certain threshold, the soil microbiome shifts. Some bacteria that may help plants grow actually increase, while others decline. This suggests ash doesn't just kill off microbial life, it reorganizes it in complex ways (Staudigel et al., 2025). These shifts matter because soil microorganisms are responsible for nearly all biogeochemical transformations, including nutrient cycling, soil formation, and organic matter decomposition, meaning that disruptions to microbial communities have cascading effects on the broader ecosystem (Staudigel et al., 2025).

These environmental changes caused by ashfall do not stay contained in the soil. They also extend into water systems, such as rivers, lakes, and reservoirs, and ultimately reach human homes and human systems. When ash falls into water supplies, it increases acidity and releases soluble contaminants, including fluoride, iron, sulphate, and chloride, into drinking water (Stewart et al., 2006). It also increases turbidity, which is dangerous because the ash particles present interfere with the disinfection process, allowing harmful bacteria to survive in the water (Stewart et al., 2006). This raises the risk of waterborne disease outbreaks (Stewart et al., 2006). Aside from water contamination, the restructuring of soil microbial communities also affects food systems. Changes in soil chemistry disrupt nutrient cycling, which reduces soil fertility and can lower crop yields. On top of this, volcanic air pollution has been linked to respiratory illness, cardiovascular effects, and increased healthcare visits in exposed populations (Stewart et al., 2022). This shows that the path from environmental disruption to human health outcomes works through several pathways at once, not just one (Stewart et al., 2022). Together, these interconnections show that the health impacts of volcanic ash cannot be understood by looking at geology, microbiology, or human health on their own; they are fundamentally linked.

== Conclusions ==

==References==
<references />
Baxter, P. J., Ing, R., Falk, H., & Plikaytis, B. (1983). Mount St. Helens eruptions: The acute respiratory effects of volcanic ash in a North American community. Archives of Environmental Health, 38(3), 138–143. https://doi.org/10.1080/00039896.1983.10543892

Durant, A. J., Bonadonna, C., & Horwell, C. J. (2010). Atmospheric and Environmental Impacts of Volcanic Particulates. Elements, 6(4), 235–240. https://doi.org/10.2113/gselements.6.4.235

Fiantis, D., Ginting, F. I., Gusnidar, G., Nelson, M., & Van Ranst, E. (2019). ''Volcanic ash, soil formation, and ecosystem development.''

Horwell, C. J., & Baxter, P. J. (2006). The respiratory health hazards of volcanic ash: a review for volcanic risk mitigation. Bulletin of Volcanology, 69(1), 1–24. https://doi.org/10.1007/s00445-006-0052-y

Newhall, C. G., & Punongbayan, R. S. (1997). ''The cataclysmic 1991 eruption of Mount Pinatubo, Philippines''. U.S. Geological Survey Fact Sheet 113-97.

Maltz, M.R., Allen, M.F., Phillips, M.L., Hernandez, R.R., Shulman, H.B., Freund, L., Andrews, L.V., Botthoff, J.K., and Aronson, E.L. (2024). Microbial community structure in recovering forests of Mount St. Helens. Frontiers in Microbiomes, 3, 1399416. https://doi.org/10.3389/frmbi.2024.1399416

Monick, M. M., Baltrusaitis, J., Powers, L. S., Borcherding, J. A., Caraballo, J. C., Mudunkotuwa, I., Peate, D. W., Walters, K., Thompson, J. M., Grassian, V. H., Gudmundsson, G., & Comellas, A. P. (2013). Effects of Eyjafjallajökull Volcanic Ash on Innate Immune System Responses and Bacterial Growth in Vitro. ''Environmental Health Perspectives'', ''121''(6), 691–698. https://doi.org/10.1289/ehp.1206004.

Shezi, B., Mathee, A., Cele, N., Ndabandaba, S., & Street, R. A. (2020). Occupational Exposure to Fine Particulate Matter (PM4 and PM2.5) during Hand-Made Cookware Operation: Personal, Indoor and Outdoor Levels. International journal of environmental research and public health, 17(20), 7522. <nowiki>https://doi.org/10.3390/ijerph17207522</nowiki>

Stewart, C., Johnston, D. M., Leonard, G. S., Horwell, C. J., Thordarson, T., & Cronin, S. J. (2006). ''Contamination of water supplies by volcanic ashfall: A literature review and simple impact modelling.''

U.S. Geological Survey. (n.d.). ''Volcanic ash impacts & mitigation: Eyes and skin''. U.S. Department of the Interior. <nowiki>https://volcanoes.usgs.gov/volcanic_ash/eye_skin.html</nowiki>

U.S. Geological Survey. (2023). ''1980 Cataclysmic Eruption''. Retrieved from <nowiki>https://www.usgs.gov/volcanoes/mount-st.-helens/science/1980-cataclysmic-eruption</nowiki>

Canadian Lung Association. ''Your lungs'' [Image]. Canadian Lung Association. <nowiki>https://www.lung.ca/how-to-protect-your-lungs/your-lungs/</nowiki>

U.S. Geological Survey. (2017, December 13). ''Illustration of the basic process of magma formation, movement to the surface, and eruption through a volcanic vent'' [Illustration]. <nowiki>https://www.usgs.gov/media/images/illustration-basic-process-magma-formation-movement-s</nowiki>

U.S. Geological Survey. (2015, November 13). ''Scanning electron microscope image of volcanic ash'' [Photograph]. <nowiki>https://www.usgs.gov/media/images/scanning-electron-microscope-image-volcanic-ash</nowiki>

Fiantis, D., Ginting, F. I., Gusnidar, Nelson, M., & Minasny, B. (2019). ''Volcanic ash, insecurity for the people but securing fertile soil for the future''. ''Sustainability, 11''(11), 3072. <nowiki>https://doi.org/10.3390/su11113072</nowiki>

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Course:EOSC311/2026/Volcanic Ash Composition and its effects on Human Health and Microbial Ecosystems

2026-06-18T03:02:27Z

RAJMEHRA: citations

== Introduction ==
Volcanic eruptions are mighty natural forces that are able to cause vast changes in ecosystems and the atmosphere. Volcanoes, when they erupt, release large amounts of volcanic ash, volcanic gases, and fragments of rocks that are able to be spread over long distances through many mediums like wind and water, affecting not only local but also global scales. Most of the time, volcanoes are talked about from a geological perspective, but the impacts of volcanoes go beyond simple things like land creation. Volcanic emissions can have an influence on air, water, and soil quality that can have an impact on both human health and the microbial ecosystem. This project looks at the connections between volcanic geology, human health and microbiology by exploring how volcanic ash materials have an impact on respiratory and immune systems, as well as microbial ecosystems.

==Volcanic Ash Composition==

=== 2.1 Formation of Volcanic Ash ===
[[File:VolcanoImage.jpg|thumb|The process by which volcanic ash forms, starting from magma ascending from the mantle to the surface of the Earth. Source: U.S. Geological Survey (Public Domain).]]
Magma is molten rock found beneath the Earth's surface that contains dissolved gases, including water vapor, carbon dioxide (CO₂), and sulfur dioxide (SO₂). As magma rises toward the surface, pressure decreases, causing these gases to escape and form bubbles known as vesicles, similar to how a carbonated drink fizzes when opened. When magma rises quickly, pressure builds up inside these bubbles until they burst, breaking the magma into fine particles known as volcanic ash (Durant et al., 2010). The composition of the magma affects how explosive the eruption is — magmas with high silica content tend to erupt more explosively, producing larger amounts of ash.
=== 2.2 Particle Size and Structure ===
During an explosive volcanic eruption, rocks, mineral fragments, and/or ash are ejected into the air; these are known as pyroclasts. Volcanic ash is defined as pyroclasts with a diameter of 2mm or less, an important factor in determining how hazardous the ash is to human health. The size is measured using aerodynamic diameter, and particles are classified into two key health-relevant categories: thoracic particles (PM10), which are less than 10 μm in diameter, and respirable particles (PM4), which are less than 4 μm in diameter (Horwell & Baxter, 2006). The percentage of respirable material in ash varies considerably depending on the volcano, the explosivity of the eruption, and the distance from the vent at which ash is collected (Horwell & Baxter, 2006).
[[File:VolcanicAsh.jpg|thumb|The shape and size of volcanic ash under a microscope with a 50 micrometre scale bar. Source: U.S. Geological Survey (Public Domain).]]
Fine ash particles tend to fall in loose clusters of less than 100 μm, which break apart easily when they hit the ground or when they get disturbed by external factors, such as wind, passing vehicles, or everyday human activity (Horwell & Baxter, 2006). This means that ash that has already settled on the ground can be lifted back into the air and inhaled all over again, making exposure an ongoing cycle even after an eruption has ended. The irregular shape of these particles also makes them more physically damaging once inhaled, as their sharp edges can irritate and damage the lining of the airways (Horwell & Baxter, 2006). Together, these structural properties, combined with how small respirable particles are, make volcanic ash particularly harmful to the respiratory system.

=== 2.3 Chemical and Mineral Composition ===
Volcanic ash is not made up from a single uniform material; its chemical and mineral composition varies depending on the type of magma that erupted and the nature of the eruption. Ash is made up of three main components: glass, which is a quenched (rapidly cooled) melt; lithic fragments, which are pieces of pre-existing rock from the volcanic vent; and crystals, which are minerals that formed within the magma before the eruption (Durant et al., 2010). The crystal component can include minerals such as quartz, feldspar, pyroxenes, amphiboles, and olivine, with the exact proportions depending on the magma composition.

One of the most important and dangerous components of volcanic ash is crystalline silica, which can appear as quartz, cristobalite, or tridymite (Horwell & Baxter, 2006). Cristobalite is considered the most toxic of these forms and is particularly common in volcanoes. It forms through a process called devitrification, the conversion of volcanic glass into crystalline material (Horwell & Baxter, 2006).

Aside from crystalline silica, volcanic ash also carries a range of trace elements and chemical species on its surface (Durant et al., 2010). During an eruption, gases such as fluorine, sulfur dioxide, and hydrogen chloride interact with ash particles, leaving chemical coatings on the surface of the ash (Durant et al., 2010). These surface chemicals can be rapidly released when ash comes into contact with water, contaminating water supplies and soil environments. The presence of iron on ash surfaces is also significant, as it can generate harmful free radicals when it interacts with the lung, potentially causing cell damage even in ash that contains little to no crystalline silica (Horwell & Baxter, 2006).

== Notable Volcanic Eruptions ==

=== 3.1 Mount St. Helens ===
[[File:Vhp img571.jpg|thumb|Mout St. Helens eruption on May 18, 1980, showing the volcanic ash plume produced during the eruption. Source: U.S. Geological Survey (Public Domain).]]
The eruption of Mount St. Helen in Washington, USA, on May 19, 1980, is considered one of the most significant volcanic eruptions in modern history. Following a magnitude 5.1 earthquake, the volcano experienced a lateral blast that destroyed large areas surrounding the mountain. The eruption produced approximately 540 million tons of volcanic ash, which spread across much of the United States and even circled the globe within weeks. The eruption produced a large ash cloud that caused transportation disruptions, environmental damage, and respiratory health concerns (U.S. Geological Survey [USGS], 2023). The event demonstrated how volcanic ash can affect areas far beyond the immediate vicinity of a volcano and remains an important case study for volcanic hazard research.

=== 3.2 Comparison of Major Ash- Producing Eruption ===
Several volcanic eruptions have produced significant amounts of ash, including Mount St. Helens (1980), Mount Pinatubo (1991), and Eyjafjallajökull (2010). While Mount St. Helens caused major regional impacts, Mount Pinatubo had global climate effects due to the large volume of ash and gas released into the atmosphere. In contrast Eyjafjallajökull primarily disrupted air travel across Europe. These eruptions highlight the diverse environmental health and economic impacts that volcanic ash can produce (Newhall & Punongbayan, 1997).

== Effects on Human Health ==

=== 4.1 Respiratory Effects ===
[[File:LungDiagram.jpg|thumb|The human respiratory system, specifically the Alveoli. Source: Canadian Lung Association]]
The respiratory systems are direct targets for volcanic ash due to the ease of inhalation of these tiny particles and their sheer abundance when released. Respirable particles are of greatest concern. These respirable particles, due to their size of around 1/20th the width of a human hair, are capable of being suspended in the air for an extensive amount of time (Shezi et al., 2020). Because of this size, they are fine enough to penetrate deep into the alveolar region of the lungs, where they have the greatest toxic potential (Horwell & Baxter, 2006).

Once these particles reach these alveloar regions, they interact with the cells of the immune system. Resident macrophages and mast cells act as the first line of defense, the primary response, to the inhaled particles. These immune cells are working hard, engulfing these particles, in a process named phagocytosis. The issue is that, when volcanoes release volcanic ash, it does not release only a few particles. The large quantities of ash that are present in the air after an eruption, and the amount of particles inhaled at once, make it difficult for macrophages and mast cells to remove all of them. Due to this, there is a release of cytokines that aim to recruit other immune cells to initiate the second line of defense, but this results in '''something''' inflammation. This inflammatory response that occurs leads to unwanted effects of swelling or irritation in the lungs that causes coughing or shortness of breath (Horwell & Baxter, 2006).

In addition to these respirable particles, exposure to crystalline silica has been studied throughout occupational medicine and has been determined as a cause of silicosis, a serious fibrotic lung disease, and prolonged exposure may also increase the risk of lung cancer (Horwell & Baxter, 2006). This makes the crystalline silica content of ash one of the most critical factors in assessing its health hazard. Repeated exposure to these particles (like seen in people from these volcanic regions that we mentioned above?) can cause chronic respiratory damage.

=== 4.2 Eye and Skin Irritation ===
Volcanic ash also has the ability to impact the eyes and skin. Volcanic ash frequently contains sharp objects that are able to scratch sensitive surfaces when they come into contact. The eyes being exposed to these volcanic ash particles is said to cause unfavourable symptoms like corneal abrasions or scratches, which can cause severe eye pain, conjunctivitis, and more. The skin is also another surface that volcanic ash can attack. When ash comes into contact with the skin, it can cause irritation and reddening of the skin (U.S. Geological Survey).

=== 4.3 Immune Systems ===
The impacts of volcanic ash exposure are noticeable on both the respiratory and eye and skin levels. But the impacts of volcanic ash are able to go beyond and are shown to damage the immune system as a whole. As mentioned before, the primary and secondary responses are how the body is able to fight off bacteria that manage to enter to prevent infections from occurring. What is interesting is that it has been shown that the properties of volcanic ash may play a role in interfering with these systems (Monick et al., 2013).

Macrophages, the first line of defense, play a role in engulfing foreign particles in a process named phagocytosis. Research shows that volcanic ash is actually able to impair macrophages from performing their task, resulting in a reduced ability to remove these foreign particles (Monick et al., 2013). This reduced ability allows for more particles to be present in the body, increasing the chances of infection and other negative effects.

With volcanic ash carrying a range of trace elements like iron, it can actually provide a source of nutrients that bacteria can use to grow and survive inside the body (Monick et al., 2013).

== Effects on Microbial Ecosystem ==

=== 5.1 Soil Microbial Communities ===
Volcanic ash can significantly affect soil microbial communities by altering soil chemistry, pH, moisture retention, and nutrient availability. Immediately after an eruption, thick layer of ash may reduce microbial activity by covering existing soil and limiting access to oxygen and different organic matter. As a result, the abundance and diversity of microorganisms often decrease in the short term (Fiantis et al., 2019).

However, volcanic ash also contains minerals such as iron, magnesium, potassium, and phosphorus that can gradually improve soil fertility. As weathering occurs, these nutrients are released into the soil and become available to microorganisms. Certain bacteria and fungi are able to colonize newly formed volcanic deposits and play an important role in breaking down minerals, cycling nutrients, and supporting soil development. Over time, microbial communities help create conditions that allow plants and other organisms to establish themselves, contributing to ecosystem recovery (Fiantis et al., 2019).

Volcanic ash can have both positive and negative impacts on soil microbial ecosystems, depending on whether the effects are considered in the short term or the long term.

=== 5.2 Water Contamination ===
Volcanic ash can enter rivers, lakes and ground water through rainfall. Ash particles may increase water turbidity and alter water chemistry, affecting microorganisms that live in aquatic environments. Also, high concentrations of ash can reduce light penetration and sirupt microbial processes that are important for maintaining water quality and ecosystem health (Stewart et al, 2006).

Furthermore, volcanic ash may change the chemical composition of water by releasing minerals and other substances. These changes can alter the balance of microbial communities, causing some species to decline while others become more abundant. As a result normal nutrient cycling and other ecological processes carried out by microorganisms may be disrupted until the ecosystem gradually recovers (Stewart et al., 2006).

=== 5.3 Recovery and Adaptation ===
Although volcanic eruptions can initially disrupt microbial ecosystems, many microorganisms are capable of adapting to the new environmental conditions. Over time, microbial communities recolonize ash- covered areas and contribute to soil formation and nutrient cycling. This recovery process helps establish conditions that support plant growth and the gradual restoration of affected ecosystems (Fiantis et al., 2019).

== Interconnections Between Human Health and Microbial Ecosystem ==

When volcanic ash is deposited onto soil and water environments, it does not settle as an inert layer. Instead, it restructures the chemical and biological conditions of the microbial communities in that area. Ash alters the carbon and nitrogen concentrations in the soil, changes the pH, and introduces new minerals and trace elements, thereby affecting which microorganisms survive and thrive (Maltz et al., 2024). Various studies were conducted following the 1980 eruption of Mount St. Helens. These studies showed that microbial communities remained fundamentally restructured for decades, with bacterial and fungal composition varying significantly with ashfall intensity and soil chemistry (Maltz et al., 2024). Along with these studies, research on volcanic ash fertilization was also being conducted. These studies showed that once ash concentrations pass a certain threshold, the soil microbiome shifts. Some bacteria that may help plants grow actually increase, while others decline. This suggests ash doesn't just kill off microbial life, it reorganizes it in complex ways (Staudigel et al., 2025). These shifts matter because soil microorganisms are responsible for nearly all biogeochemical transformations, including nutrient cycling, soil formation, and organic matter decomposition, meaning that disruptions to microbial communities have cascading effects on the broader ecosystem (Staudigel et al., 2025).

These environmental changes caused by ashfall do not stay contained in the soil. They also extend into water systems, such as rivers, lakes, and reservoirs, and ultimately reach human homes and human systems. When ash falls into water supplies, it increases acidity and releases soluble contaminants, including fluoride, iron, sulphate, and chloride, into drinking water (Stewart et al., 2006). It also increases turbidity, which is dangerous because the ash particles present interfere with the disinfection process, allowing harmful bacteria to survive in the water (Stewart et al., 2006). This raises the risk of waterborne disease outbreaks (Stewart et al., 2006). Aside from water contamination, the restructuring of soil microbial communities also affects food systems. Changes in soil chemistry disrupt nutrient cycling, which reduces soil fertility and can lower crop yields. On top of this, volcanic air pollution has been linked to respiratory illness, cardiovascular effects, and increased healthcare visits in exposed populations (Stewart et al., 2022). This shows that the path from environmental disruption to human health outcomes works through several pathways at once, not just one (Stewart et al., 2022). Together, these interconnections show that the health impacts of volcanic ash cannot be understood by looking at geology, microbiology, or human health on their own; they are fundamentally linked.

== Conclusions ==

==References==
<references />
Baxter, P. J., Ing, R., Falk, H., & Plikaytis, B. (1983). Mount St. Helens eruptions: The acute respiratory effects of volcanic ash in a North American community. Archives of Environmental Health, 38(3), 138–143. https://doi.org/10.1080/00039896.1983.10543892

Durant, A. J., Bonadonna, C., & Horwell, C. J. (2010). Atmospheric and Environmental Impacts of Volcanic Particulates. Elements, 6(4), 235–240. https://doi.org/10.2113/gselements.6.4.235

Fiantis, D., Ginting, F. I., Gusnidar, G., Nelson, M., & Van Ranst, E. (2019). ''Volcanic ash, soil formation, and ecosystem development.''

Horwell, C. J., & Baxter, P. J. (2006). The respiratory health hazards of volcanic ash: a review for volcanic risk mitigation. Bulletin of Volcanology, 69(1), 1–24. https://doi.org/10.1007/s00445-006-0052-y

Newhall, C. G., & Punongbayan, R. S. (1997). ''The cataclysmic 1991 eruption of Mount Pinatubo, Philippines''. U.S. Geological Survey Fact Sheet 113-97.

Maltz, M.R., Allen, M.F., Phillips, M.L., Hernandez, R.R., Shulman, H.B., Freund, L., Andrews, L.V., Botthoff, J.K., and Aronson, E.L. (2024). Microbial community structure in recovering forests of Mount St. Helens. Frontiers in Microbiomes, 3, 1399416. https://doi.org/10.3389/frmbi.2024.1399416

Monick, M. M., Baltrusaitis, J., Powers, L. S., Borcherding, J. A., Caraballo, J. C., Mudunkotuwa, I., Peate, D. W., Walters, K., Thompson, J. M., Grassian, V. H., Gudmundsson, G., & Comellas, A. P. (2013). Effects of Eyjafjallajökull Volcanic Ash on Innate Immune System Responses and Bacterial Growth in Vitro. ''Environmental Health Perspectives'', ''121''(6), 691–698. https://doi.org/10.1289/ehp.1206004.

Shezi, B., Mathee, A., Cele, N., Ndabandaba, S., & Street, R. A. (2020). Occupational Exposure to Fine Particulate Matter (PM4 and PM2.5) during Hand-Made Cookware Operation: Personal, Indoor and Outdoor Levels. International journal of environmental research and public health, 17(20), 7522. <nowiki>https://doi.org/10.3390/ijerph17207522</nowiki>

Stewart, C., Johnston, D. M., Leonard, G. S., Horwell, C. J., Thordarson, T., & Cronin, S. J. (2006). ''Contamination of water supplies by volcanic ashfall: A literature review and simple impact modelling.''

U.S. Geological Survey. (n.d.). ''Volcanic ash impacts & mitigation: Eyes and skin''. U.S. Department of the Interior. <nowiki>https://volcanoes.usgs.gov/volcanic_ash/eye_skin.html</nowiki>

U.S. Geological Survey. (2023). ''1980 Cataclysmic Eruption''. Retrieved from <nowiki>https://www.usgs.gov/volcanoes/mount-st.-helens/science/1980-cataclysmic-eruption</nowiki>

Canadian Lung Association. ''Your lungs'' [Image]. Canadian Lung Association. <nowiki>https://www.lung.ca/how-to-protect-your-lungs/your-lungs/</nowiki>

U.S. Geological Survey. (2017, December 13). ''Illustration of the basic process of magma formation, movement to the surface, and eruption through a volcanic vent'' [Illustration]. <nowiki>https://www.usgs.gov/media/images/illustration-basic-process-magma-formation-movement-s</nowiki>

U.S. Geological Survey. (2015, November 13). ''Scanning electron microscope image of volcanic ash'' [Photograph]. <nowiki>https://www.usgs.gov/media/images/scanning-electron-microscope-image-volcanic-ash</nowiki>

‌

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File:LungDiagram.jpg

2026-06-18T02:58:32Z

RAJMEHRA: Uploaded a work by Canadian Lung Association from https://www.lung.ca/how-to-protect-your-lungs/your-lungs/ with UploadWizard

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Course:EOSC311/2026/Volcanic Ash Composition and its effects on Human Health and Microbial Ecosystems

2026-06-18T02:53:03Z

RAJMEHRA: image

== Introduction ==
Volcanic eruptions are mighty natural forces that are able to cause vast changes in ecosystems and the atmosphere. Volcanoes, when they erupt, release large amounts of volcanic ash, volcanic gases, and fragments of rocks that are able to be spread over long distances through many mediums like wind and water, affecting not only local but also global scales. Most of the time, volcanoes are talked about from a geological perspective, but the impacts of volcanoes go beyond simple things like land creation. Volcanic emissions can have an influence on air, water, and soil quality that can have an impact on both human health and the microbial ecosystem. This project looks at the connections between volcanic geology, human health and microbiology by exploring how volcanic ash materials have an impact on respiratory and immune systems, as well as microbial ecosystems.

==Volcanic Ash Composition==

=== 2.1 Formation of Volcanic Ash ===
[[File:VolcanoImage.jpg|thumb|The process by which volcanic ash forms, starting from magma ascending from the mantle to the surface of the Earth. Source: U.S. Geological Survey (Public Domain).]]
Magma is molten rock found beneath the Earth's surface that contains dissolved gases, including water vapor, carbon dioxide (CO₂), and sulfur dioxide (SO₂). As magma rises toward the surface, pressure decreases, causing these gases to escape and form bubbles known as vesicles, similar to how a carbonated drink fizzes when opened. When magma rises quickly, pressure builds up inside these bubbles until they burst, breaking the magma into fine particles known as volcanic ash (Durant et al., 2010). The composition of the magma affects how explosive the eruption is — magmas with high silica content tend to erupt more explosively, producing larger amounts of ash.
=== 2.2 Particle Size and Structure ===
During an explosive volcanic eruption, rocks, mineral fragments, and/or ash are ejected into the air; these are known as pyroclasts. Volcanic ash is defined as pyroclasts with a diameter of 2mm or less, an important factor in determining how hazardous the ash is to human health. The size is measured using aerodynamic diameter, and particles are classified into two key health-relevant categories: thoracic particles (PM10), which are less than 10 μm in diameter, and respirable particles (PM4), which are less than 4 μm in diameter (Horwell & Baxter, 2006). The percentage of respirable material in ash varies considerably depending on the volcano, the explosivity of the eruption, and the distance from the vent at which ash is collected (Horwell & Baxter, 2006).
[[File:VolcanicAsh.jpg|thumb|The shape and size of volcanic ash under a microscope with a 50 micrometre scale bar. Source: U.S. Geological Survey (Public Domain).]]
Fine ash particles tend to fall in loose clusters of less than 100 μm, which break apart easily when they hit the ground or when they get disturbed by external factors, such as wind, passing vehicles, or everyday human activity (Horwell & Baxter, 2006). This means that ash that has already settled on the ground can be lifted back into the air and inhaled all over again, making exposure an ongoing cycle even after an eruption has ended. The irregular shape of these particles also makes them more physically damaging once inhaled, as their sharp edges can irritate and damage the lining of the airways (Horwell & Baxter, 2006). Together, these structural properties, combined with how small respirable particles are, make volcanic ash particularly harmful to the respiratory system.

=== 2.3 Chemical and Mineral Composition ===
Volcanic ash is not made up from a single uniform material; its chemical and mineral composition varies depending on the type of magma that erupted and the nature of the eruption. Ash is made up of three main components: glass, which is a quenched (rapidly cooled) melt; lithic fragments, which are pieces of pre-existing rock from the volcanic vent; and crystals, which are minerals that formed within the magma before the eruption (Durant et al., 2010). The crystal component can include minerals such as quartz, feldspar, pyroxenes, amphiboles, and olivine, with the exact proportions depending on the magma composition.

One of the most important and dangerous components of volcanic ash is crystalline silica, which can appear as quartz, cristobalite, or tridymite (Horwell & Baxter, 2006). Cristobalite is considered the most toxic of these forms and is particularly common in volcanoes. It forms through a process called devitrification, the conversion of volcanic glass into crystalline material (Horwell & Baxter, 2006).

Aside from crystalline silica, volcanic ash also carries a range of trace elements and chemical species on its surface (Durant et al., 2010). During an eruption, gases such as fluorine, sulfur dioxide, and hydrogen chloride interact with ash particles, leaving chemical coatings on the surface of the ash (Durant et al., 2010). These surface chemicals can be rapidly released when ash comes into contact with water, contaminating water supplies and soil environments. The presence of iron on ash surfaces is also significant, as it can generate harmful free radicals when it interacts with the lung, potentially causing cell damage even in ash that contains little to no crystalline silica (Horwell & Baxter, 2006).

== Notable Volcanic Eruptions ==

=== 3.1 Mount St. Helens ===
[[File:Vhp img571.jpg|thumb|Mout St. Helens eruption on May 18, 1980, showing the volcanic ash plume produced during the eruption. Source: U.S. Geological Survey (Public Domain).]]
The eruption of Mount St. Helen in Washington, USA, on May 19, 1980, is considered one of the most significant volcanic eruptions in modern history. Following a magnitude 5.1 earthquake, the volcano experienced a lateral blast that destroyed large areas surrounding the mountain. The eruption produced approximately 540 million tons of volcanic ash, which spread across much of the United States and even circled the globe within weeks. The eruption produced a large ash cloud that caused transportation disruptions, environmental damage, and respiratory health concerns (U.S. Geological Survey [USGS], 2023). The event demonstrated how volcanic ash can affect areas far beyond the immediate vicinity of a volcano and remains an important case study for volcanic hazard research.

=== 3.2 Comparison of Major Ash- Producing Eruption ===
Several volcanic eruptions have produced significant amounts of ash, including Mount St. Helens (1980), Mount Pinatubo (1991), and Eyjafjallajökull (2010). While Mount St. Helens caused major regional impacts, Mount Pinatubo had global climate effects due to the large volume of ash and gas released into the atmosphere. In contrast Eyjafjallajökull primarily disrupted air travel across Europe. These eruptions highlight the diverse environmental health and economic impacts that volcanic ash can produce (Newhall & Punongbayan, 1997).

== Effects on Human Health ==

=== 4.1 Respiratory Effects ===
The respiratory systems are direct targets for volcanic ash due to the ease of inhalation of these tiny particles and their sheer abundance when released. Respirable particles are of greatest concern. These respirable particles, due to their size of around 1/20th the width of a human hair, are capable of being suspended in the air for an extensive amount of time (Shezi et al., 2020). Because of this size, they are fine enough to penetrate deep into the alveolar region of the lungs, where they have the greatest toxic potential (Horwell & Baxter, 2006).

Once these particles reach these alveloar regions, they interact with the cells of the immune system. Resident macrophages and mast cells act as the first line of defense, the primary response, to the inhaled particles. These immune cells are working hard, engulfing these particles, in a process named phagocytosis. The issue is that, when volcanoes release volcanic ash, it does not release only a few particles. The large quantities of ash that are present in the air after an eruption, and the amount of particles inhaled at once, make it difficult for macrophages and mast cells to remove all of them. Due to this, there is a release of cytokines that aim to recruit other immune cells to initiate the second line of defense, but this results in '''something''' inflammation. This inflammatory response that occurs leads to unwanted effects of swelling or irritation in the lungs that causes coughing or shortness of breath (Horwell & Baxter, 2006).

In addition to these respirable particles, exposure to crystalline silica has been studied throughout occupational medicine and has been determined as a cause of silicosis, a serious fibrotic lung disease, and prolonged exposure may also increase the risk of lung cancer (Horwell & Baxter, 2006). This makes the crystalline silica content of ash one of the most critical factors in assessing its health hazard. Repeated exposure to these particles (like seen in people from these volcanic regions that we mentioned above?) can cause chronic respiratory damage.

=== 4.2 Eye and Skin Irritation ===
Volcanic ash also has the ability to impact the eyes and skin. Volcanic ash frequently contains sharp objects that are able to scratch sensitive surfaces when they come into contact. The eyes being exposed to these volcanic ash particles is said to cause unfavourable symptoms like corneal abrasions or scratches, which can cause severe eye pain, conjunctivitis, and more. The skin is also another surface that volcanic ash can attack. When ash comes into contact with the skin, it can cause irritation and reddening of the skin (U.S. Geological Survey).

=== 4.3 Immune Systems ===
The impacts of volcanic ash exposure are noticeable on both the respiratory and eye and skin levels. But the impacts of volcanic ash are able to go beyond and are shown to damage the immune system as a whole. As mentioned before, the primary and secondary responses are how the body is able to fight off bacteria that manage to enter to prevent infections from occurring. What is interesting is that it has been shown that the properties of volcanic ash may play a role in interfering with these systems (Monick et al., 2013).

Macrophages, the first line of defense, play a role in engulfing foreign particles in a process named phagocytosis. Research shows that volcanic ash is actually able to impair macrophages from performing their task, resulting in a reduced ability to remove these foreign particles (Monick et al., 2013). This reduced ability allows for more particles to be present in the body, increasing the chances of infection and other negative effects.

With volcanic ash carrying a range of trace elements like iron, it can actually provide a source of nutrients that bacteria can use to grow and survive inside the body (Monick et al., 2013).

== Effects on Microbial Ecosystem ==

=== 5.1 Soil Microbial Communities ===
Volcanic ash can significantly affect soil microbial communities by altering soil chemistry, pH, moisture retention, and nutrient availability. Immediately after an eruption, thick layer of ash may reduce microbial activity by covering existing soil and limiting access to oxygen and different organic matter. As a result, the abundance and diversity of microorganisms often decrease in the short term (Fiantis et al., 2019).

However, volcanic ash also contains minerals such as iron, magnesium, potassium, and phosphorus that can gradually improve soil fertility. As weathering occurs, these nutrients are released into the soil and become available to microorganisms. Certain bacteria and fungi are able to colonize newly formed volcanic deposits and play an important role in breaking down minerals, cycling nutrients, and supporting soil development. Over time, microbial communities help create conditions that allow plants and other organisms to establish themselves, contributing to ecosystem recovery (Fiantis et al., 2019).

Volcanic ash can have both positive and negative impacts on soil microbial ecosystems, depending on whether the effects are considered in the short term or the long term.

=== 5.2 Water Contamination ===
Volcanic ash can enter rivers, lakes and ground water through rainfall. Ash particles may increase water turbidity and alter water chemistry, affecting microorganisms that live in aquatic environments. Also, high concentrations of ash can reduce light penetration and sirupt microbial processes that are important for maintaining water quality and ecosystem health (Stewart et al, 2006).

Furthermore, volcanic ash may change the chemical composition of water by releasing minerals and other substances. These changes can alter the balance of microbial communities, causing some species to decline while others become more abundant. As a result normal nutrient cycling and other ecological processes carried out by microorganisms may be disrupted until the ecosystem gradually recovers (Stewart et al., 2006).

=== 5.3 Recovery and Adaptation ===
Although volcanic eruptions can initially disrupt microbial ecosystems, many microorganisms are capable of adapting to the new environmental conditions. Over time, microbial communities recolonize ash- covered areas and contribute to soil formation and nutrient cycling. This recovery process helps establish conditions that support plant growth and the gradual restoration of affected ecosystems (Fiantis et al., 2019).

== Interconnections Between Human Health and Microbial Ecosystem ==

When volcanic ash is deposited onto soil and water environments, it does not settle as an inert layer. Instead, it restructures the chemical and biological conditions of the microbial communities in that area. Ash alters the carbon and nitrogen concentrations in the soil, changes the pH, and introduces new minerals and trace elements, thereby affecting which microorganisms survive and thrive (Maltz et al., 2024). Various studies were conducted following the 1980 eruption of Mount St. Helens. These studies showed that microbial communities remained fundamentally restructured for decades, with bacterial and fungal composition varying significantly with ashfall intensity and soil chemistry (Maltz et al., 2024). Along with these studies, research on volcanic ash fertilization was also being conducted. These studies showed that once ash concentrations pass a certain threshold, the soil microbiome shifts. Some bacteria that may help plants grow actually increase, while others decline. This suggests ash doesn't just kill off microbial life, it reorganizes it in complex ways (Staudigel et al., 2025). These shifts matter because soil microorganisms are responsible for nearly all biogeochemical transformations, including nutrient cycling, soil formation, and organic matter decomposition, meaning that disruptions to microbial communities have cascading effects on the broader ecosystem (Staudigel et al., 2025).

These environmental changes caused by ashfall do not stay contained in the soil. They also extend into water systems, such as rivers, lakes, and reservoirs, and ultimately reach human homes and human systems. When ash falls into water supplies, it increases acidity and releases soluble contaminants, including fluoride, iron, sulphate, and chloride, into drinking water (Stewart et al., 2006). It also increases turbidity, which is dangerous because the ash particles present interfere with the disinfection process, allowing harmful bacteria to survive in the water (Stewart et al., 2006). This raises the risk of waterborne disease outbreaks (Stewart et al., 2006). Aside from water contamination, the restructuring of soil microbial communities also affects food systems. Changes in soil chemistry disrupt nutrient cycling, which reduces soil fertility and can lower crop yields. On top of this, volcanic air pollution has been linked to respiratory illness, cardiovascular effects, and increased healthcare visits in exposed populations (Stewart et al., 2022). This shows that the path from environmental disruption to human health outcomes works through several pathways at once, not just one (Stewart et al., 2022). Together, these interconnections show that the health impacts of volcanic ash cannot be understood by looking at geology, microbiology, or human health on their own; they are fundamentally linked.

== Conclusions ==

==References==
<references />
Baxter, P. J., Ing, R., Falk, H., & Plikaytis, B. (1983). Mount St. Helens eruptions: The acute respiratory effects of volcanic ash in a North American community. Archives of Environmental Health, 38(3), 138–143. https://doi.org/10.1080/00039896.1983.10543892

Durant, A. J., Bonadonna, C., & Horwell, C. J. (2010). Atmospheric and Environmental Impacts of Volcanic Particulates. Elements, 6(4), 235–240. https://doi.org/10.2113/gselements.6.4.235

Fiantis, D., Ginting, F. I., Gusnidar, G., Nelson, M., & Van Ranst, E. (2019). ''Volcanic ash, soil formation, and ecosystem development.''

Horwell, C. J., & Baxter, P. J. (2006). The respiratory health hazards of volcanic ash: a review for volcanic risk mitigation. Bulletin of Volcanology, 69(1), 1–24. https://doi.org/10.1007/s00445-006-0052-y

Newhall, C. G., & Punongbayan, R. S. (1997). ''The cataclysmic 1991 eruption of Mount Pinatubo, Philippines''. U.S. Geological Survey Fact Sheet 113-97.

Maltz, M.R., Allen, M.F., Phillips, M.L., Hernandez, R.R., Shulman, H.B., Freund, L., Andrews, L.V., Botthoff, J.K., and Aronson, E.L. (2024). Microbial community structure in recovering forests of Mount St. Helens. Frontiers in Microbiomes, 3, 1399416. https://doi.org/10.3389/frmbi.2024.1399416

Monick, M. M., Baltrusaitis, J., Powers, L. S., Borcherding, J. A., Caraballo, J. C., Mudunkotuwa, I., Peate, D. W., Walters, K., Thompson, J. M., Grassian, V. H., Gudmundsson, G., & Comellas, A. P. (2013). Effects of Eyjafjallajökull Volcanic Ash on Innate Immune System Responses and Bacterial Growth in Vitro. ''Environmental Health Perspectives'', ''121''(6), 691–698. https://doi.org/10.1289/ehp.1206004.

Shezi, B., Mathee, A., Cele, N., Ndabandaba, S., & Street, R. A. (2020). Occupational Exposure to Fine Particulate Matter (PM4 and PM2.5) during Hand-Made Cookware Operation: Personal, Indoor and Outdoor Levels. International journal of environmental research and public health, 17(20), 7522. <nowiki>https://doi.org/10.3390/ijerph17207522</nowiki>

Stewart, C., Johnston, D. M., Leonard, G. S., Horwell, C. J., Thordarson, T., & Cronin, S. J. (2006). ''Contamination of water supplies by volcanic ashfall: A literature review and simple impact modelling.''

U.S. Geological Survey. (n.d.). ''Volcanic ash impacts & mitigation: Eyes and skin''. U.S. Department of the Interior. <nowiki>https://volcanoes.usgs.gov/volcanic_ash/eye_skin.html</nowiki>

U.S. Geological Survey. (2023). ''1980 Cataclysmic Eruption''. Retrieved from <nowiki>https://www.usgs.gov/volcanoes/mount-st.-helens/science/1980-cataclysmic-eruption</nowiki>

‌

‌{{Projectbox_EOSC311}}
[[Category:EOSC311]]

File:VolcanicAsh.jpg

2026-06-18T02:51:39Z

RAJMEHRA: Uploaded a work by U.S. Geological Survey from https://www.usgs.gov/media/images/scanning-electron-microscope-image-volcanic-ash with UploadWizard

=={{int:filedesc}}==
{{Information
|description={{en|1=VolcanicAsh}}
|date=2026-06-17
|source=https://www.usgs.gov/media/images/scanning-electron-microscope-image-volcanic-ash
|author=U.S. Geological Survey
|permission=
|other versions=
}}

=={{int:license-header}}==
{{cc-by-sa-4.0}}

Course:EOSC311/2026/Volcanic Ash Composition and its effects on Human Health and Microbial Ecosystems

2026-06-18T02:45:13Z

RAJMEHRA: image

== Introduction ==
Volcanic eruptions are mighty natural forces that are able to cause vast changes in ecosystems and the atmosphere. Volcanoes, when they erupt, release large amounts of volcanic ash, volcanic gases, and fragments of rocks that are able to be spread over long distances through many mediums like wind and water, affecting not only local but also global scales. Most of the time, volcanoes are talked about from a geological perspective, but the impacts of volcanoes go beyond simple things like land creation. Volcanic emissions can have an influence on air, water, and soil quality that can have an impact on both human health and the microbial ecosystem. This project looks at the connections between volcanic geology, human health and microbiology by exploring how volcanic ash materials have an impact on respiratory and immune systems, as well as microbial ecosystems.

==Volcanic Ash Composition==

=== 2.1 Formation of Volcanic Ash ===
[[File:VolcanoImage.jpg|thumb|The process by which volcanic ash forms, starting from magma ascending from the mantle to the surface of the Earth. Source: U.S. Geological Survey (Public Domain).]]
Magma is molten rock found beneath the Earth's surface that contains dissolved gases, including water vapor, carbon dioxide (CO₂), and sulfur dioxide (SO₂). As magma rises toward the surface, pressure decreases, causing these gases to escape and form bubbles known as vesicles, similar to how a carbonated drink fizzes when opened. When magma rises quickly, pressure builds up inside these bubbles until they burst, breaking the magma into fine particles known as volcanic ash (Durant et al., 2010). The composition of the magma affects how explosive the eruption is — magmas with high silica content tend to erupt more explosively, producing larger amounts of ash.
=== 2.2 Particle Size and Structure ===
During an explosive volcanic eruption, rocks, mineral fragments, and/or ash are ejected into the air; these are known as pyroclasts. Volcanic ash is defined as pyroclasts with a diameter of 2mm or less, an important factor in determining how hazardous the ash is to human health. The size is measured using aerodynamic diameter, and particles are classified into two key health-relevant categories: thoracic particles (PM10), which are less than 10 μm in diameter, and respirable particles (PM4), which are less than 4 μm in diameter (Horwell & Baxter, 2006). The percentage of respirable material in ash varies considerably depending on the volcano, the explosivity of the eruption, and the distance from the vent at which ash is collected (Horwell & Baxter, 2006).

Fine ash particles tend to fall in loose clusters of less than 100 μm, which break apart easily when they hit the ground or when they get disturbed by external factors, such as wind, passing vehicles, or everyday human activity (Horwell & Baxter, 2006). This means that ash that has already settled on the ground can be lifted back into the air and inhaled all over again, making exposure an ongoing cycle even after an eruption has ended. The irregular shape of these particles also makes them more physically damaging once inhaled, as their sharp edges can irritate and damage the lining of the airways (Horwell & Baxter, 2006). Together, these structural properties, combined with how small respirable particles are, make volcanic ash particularly harmful to the respiratory system.

=== 2.3 Chemical and Mineral Composition ===
Volcanic ash is not made up from a single uniform material; its chemical and mineral composition varies depending on the type of magma that erupted and the nature of the eruption. Ash is made up of three main components: glass, which is a quenched (rapidly cooled) melt; lithic fragments, which are pieces of pre-existing rock from the volcanic vent; and crystals, which are minerals that formed within the magma before the eruption (Durant et al., 2010). The crystal component can include minerals such as quartz, feldspar, pyroxenes, amphiboles, and olivine, with the exact proportions depending on the magma composition.

One of the most important and dangerous components of volcanic ash is crystalline silica, which can appear as quartz, cristobalite, or tridymite (Horwell & Baxter, 2006). Cristobalite is considered the most toxic of these forms and is particularly common in volcanoes. It forms through a process called devitrification, the conversion of volcanic glass into crystalline material (Horwell & Baxter, 2006).

Aside from crystalline silica, volcanic ash also carries a range of trace elements and chemical species on its surface (Durant et al., 2010). During an eruption, gases such as fluorine, sulfur dioxide, and hydrogen chloride interact with ash particles, leaving chemical coatings on the surface of the ash (Durant et al., 2010). These surface chemicals can be rapidly released when ash comes into contact with water, contaminating water supplies and soil environments. The presence of iron on ash surfaces is also significant, as it can generate harmful free radicals when it interacts with the lung, potentially causing cell damage even in ash that contains little to no crystalline silica (Horwell & Baxter, 2006).

== Notable Volcanic Eruptions ==

=== 3.1 Mount St. Helens ===
[[File:Vhp img571.jpg|thumb|Mout St. Helens eruption on May 18, 1980, showing the volcanic ash plume produced during the eruption. Source: U.S. Geological Survey (Public Domain).]]
The eruption of Mount St. Helen in Washington, USA, on May 19, 1980, is considered one of the most significant volcanic eruptions in modern history. Following a magnitude 5.1 earthquake, the volcano experienced a lateral blast that destroyed large areas surrounding the mountain. The eruption produced approximately 540 million tons of volcanic ash, which spread across much of the United States and even circled the globe within weeks. The eruption produced a large ash cloud that caused transportation disruptions, environmental damage, and respiratory health concerns (U.S. Geological Survey [USGS], 2023). The event demonstrated how volcanic ash can affect areas far beyond the immediate vicinity of a volcano and remains an important case study for volcanic hazard research.

=== 3.2 Comparison of Major Ash- Producing Eruption ===
Several volcanic eruptions have produced significant amounts of ash, including Mount St. Helens (1980), Mount Pinatubo (1991), and Eyjafjallajökull (2010). While Mount St. Helens caused major regional impacts, Mount Pinatubo had global climate effects due to the large volume of ash and gas released into the atmosphere. In contrast Eyjafjallajökull primarily disrupted air travel across Europe. These eruptions highlight the diverse environmental health and economic impacts that volcanic ash can produce (Newhall & Punongbayan, 1997).

== Effects on Human Health ==

=== 4.1 Respiratory Effects ===
The respiratory systems are direct targets for volcanic ash due to the ease of inhalation of these tiny particles and their sheer abundance when released. Respirable particles are of greatest concern. These respirable particles, due to their size of around 1/20th the width of a human hair, are capable of being suspended in the air for an extensive amount of time (Shezi et al., 2020). Because of this size, they are fine enough to penetrate deep into the alveolar region of the lungs, where they have the greatest toxic potential (Horwell & Baxter, 2006).

Once these particles reach these alveloar regions, they interact with the cells of the immune system. Resident macrophages and mast cells act as the first line of defense, the primary response, to the inhaled particles. These immune cells are working hard, engulfing these particles, in a process named phagocytosis. The issue is that, when volcanoes release volcanic ash, it does not release only a few particles. The large quantities of ash that are present in the air after an eruption, and the amount of particles inhaled at once, make it difficult for macrophages and mast cells to remove all of them. Due to this, there is a release of cytokines that aim to recruit other immune cells to initiate the second line of defense, but this results in '''something''' inflammation. This inflammatory response that occurs leads to unwanted effects of swelling or irritation in the lungs that causes coughing or shortness of breath (Horwell & Baxter, 2006).

In addition to these respirable particles, exposure to crystalline silica has been studied throughout occupational medicine and has been determined as a cause of silicosis, a serious fibrotic lung disease, and prolonged exposure may also increase the risk of lung cancer (Horwell & Baxter, 2006). This makes the crystalline silica content of ash one of the most critical factors in assessing its health hazard. Repeated exposure to these particles (like seen in people from these volcanic regions that we mentioned above?) can cause chronic respiratory damage.

=== 4.2 Eye and Skin Irritation ===
Volcanic ash also has the ability to impact the eyes and skin. Volcanic ash frequently contains sharp objects that are able to scratch sensitive surfaces when they come into contact. The eyes being exposed to these volcanic ash particles is said to cause unfavourable symptoms like corneal abrasions or scratches, which can cause severe eye pain, conjunctivitis, and more. The skin is also another surface that volcanic ash can attack. When ash comes into contact with the skin, it can cause irritation and reddening of the skin (U.S. Geological Survey).

=== 4.3 Immune Systems ===
The impacts of volcanic ash exposure are noticeable on both the respiratory and eye and skin levels. But the impacts of volcanic ash are able to go beyond and are shown to damage the immune system as a whole. As mentioned before, the primary and secondary responses are how the body is able to fight off bacteria that manage to enter to prevent infections from occurring. What is interesting is that it has been shown that the properties of volcanic ash may play a role in interfering with these systems (Monick et al., 2013).

Macrophages, the first line of defense, play a role in engulfing foreign particles in a process named phagocytosis. Research shows that volcanic ash is actually able to impair macrophages from performing their task, resulting in a reduced ability to remove these foreign particles (Monick et al., 2013). This reduced ability allows for more particles to be present in the body, increasing the chances of infection and other negative effects.

With volcanic ash carrying a range of trace elements like iron, it can actually provide a source of nutrients that bacteria can use to grow and survive inside the body (Monick et al., 2013).

== Effects on Microbial Ecosystem ==

=== 5.1 Soil Microbial Communities ===
Volcanic ash can significantly affect soil microbial communities by altering soil chemistry, pH, moisture retention, and nutrient availability. Immediately after an eruption, thick layer of ash may reduce microbial activity by covering existing soil and limiting access to oxygen and different organic matter. As a result, the abundance and diversity of microorganisms often decrease in the short term (Fiantis et al., 2019).

However, volcanic ash also contains minerals such as iron, magnesium, potassium, and phosphorus that can gradually improve soil fertility. As weathering occurs, these nutrients are released into the soil and become available to microorganisms. Certain bacteria and fungi are able to colonize newly formed volcanic deposits and play an important role in breaking down minerals, cycling nutrients, and supporting soil development. Over time, microbial communities help create conditions that allow plants and other organisms to establish themselves, contributing to ecosystem recovery (Fiantis et al., 2019).

Volcanic ash can have both positive and negative impacts on soil microbial ecosystems, depending on whether the effects are considered in the short term or the long term.

=== 5.2 Water Contamination ===
Volcanic ash can enter rivers, lakes and ground water through rainfall. Ash particles may increase water turbidity and alter water chemistry, affecting microorganisms that live in aquatic environments. Also, high concentrations of ash can reduce light penetration and sirupt microbial processes that are important for maintaining water quality and ecosystem health (Stewart et al, 2006).

Furthermore, volcanic ash may change the chemical composition of water by releasing minerals and other substances. These changes can alter the balance of microbial communities, causing some species to decline while others become more abundant. As a result normal nutrient cycling and other ecological processes carried out by microorganisms may be disrupted until the ecosystem gradually recovers (Stewart et al., 2006).

=== 5.3 Recovery and Adaptation ===
Although volcanic eruptions can initially disrupt microbial ecosystems, many microorganisms are capable of adapting to the new environmental conditions. Over time, microbial communities recolonize ash- covered areas and contribute to soil formation and nutrient cycling. This recovery process helps establish conditions that support plant growth and the gradual restoration of affected ecosystems (Fiantis et al., 2019).

== Interconnections Between Human Health and Microbial Ecosystem ==

When volcanic ash is deposited onto soil and water environments, it does not settle as an inert layer. Instead, it restructures the chemical and biological conditions of the microbial communities in that area. Ash alters the carbon and nitrogen concentrations in the soil, changes the pH, and introduces new minerals and trace elements, thereby affecting which microorganisms survive and thrive (Maltz et al., 2024). Various studies were conducted following the 1980 eruption of Mount St. Helens. These studies showed that microbial communities remained fundamentally restructured for decades, with bacterial and fungal composition varying significantly with ashfall intensity and soil chemistry (Maltz et al., 2024). Along with these studies, research on volcanic ash fertilization was also being conducted. These studies showed that once ash concentrations pass a certain threshold, the soil microbiome shifts. Some bacteria that may help plants grow actually increase, while others decline. This suggests ash doesn't just kill off microbial life, it reorganizes it in complex ways (Staudigel et al., 2025). These shifts matter because soil microorganisms are responsible for nearly all biogeochemical transformations, including nutrient cycling, soil formation, and organic matter decomposition, meaning that disruptions to microbial communities have cascading effects on the broader ecosystem (Staudigel et al., 2025).

These environmental changes caused by ashfall do not stay contained in the soil. They also extend into water systems, such as rivers, lakes, and reservoirs, and ultimately reach human homes and human systems. When ash falls into water supplies, it increases acidity and releases soluble contaminants, including fluoride, iron, sulphate, and chloride, into drinking water (Stewart et al., 2006). It also increases turbidity, which is dangerous because the ash particles present interfere with the disinfection process, allowing harmful bacteria to survive in the water (Stewart et al., 2006). This raises the risk of waterborne disease outbreaks (Stewart et al., 2006). Aside from water contamination, the restructuring of soil microbial communities also affects food systems. Changes in soil chemistry disrupt nutrient cycling, which reduces soil fertility and can lower crop yields. On top of this, volcanic air pollution has been linked to respiratory illness, cardiovascular effects, and increased healthcare visits in exposed populations (Stewart et al., 2022). This shows that the path from environmental disruption to human health outcomes works through several pathways at once, not just one (Stewart et al., 2022). Together, these interconnections show that the health impacts of volcanic ash cannot be understood by looking at geology, microbiology, or human health on their own; they are fundamentally linked.

== Conclusions ==

==References==
<references />
Baxter, P. J., Ing, R., Falk, H., & Plikaytis, B. (1983). Mount St. Helens eruptions: The acute respiratory effects of volcanic ash in a North American community. Archives of Environmental Health, 38(3), 138–143. https://doi.org/10.1080/00039896.1983.10543892

Durant, A. J., Bonadonna, C., & Horwell, C. J. (2010). Atmospheric and Environmental Impacts of Volcanic Particulates. Elements, 6(4), 235–240. https://doi.org/10.2113/gselements.6.4.235

Fiantis, D., Ginting, F. I., Gusnidar, G., Nelson, M., & Van Ranst, E. (2019). ''Volcanic ash, soil formation, and ecosystem development.''

Horwell, C. J., & Baxter, P. J. (2006). The respiratory health hazards of volcanic ash: a review for volcanic risk mitigation. Bulletin of Volcanology, 69(1), 1–24. https://doi.org/10.1007/s00445-006-0052-y

Newhall, C. G., & Punongbayan, R. S. (1997). ''The cataclysmic 1991 eruption of Mount Pinatubo, Philippines''. U.S. Geological Survey Fact Sheet 113-97.

Maltz, M.R., Allen, M.F., Phillips, M.L., Hernandez, R.R., Shulman, H.B., Freund, L., Andrews, L.V., Botthoff, J.K., and Aronson, E.L. (2024). Microbial community structure in recovering forests of Mount St. Helens. Frontiers in Microbiomes, 3, 1399416. https://doi.org/10.3389/frmbi.2024.1399416

Monick, M. M., Baltrusaitis, J., Powers, L. S., Borcherding, J. A., Caraballo, J. C., Mudunkotuwa, I., Peate, D. W., Walters, K., Thompson, J. M., Grassian, V. H., Gudmundsson, G., & Comellas, A. P. (2013). Effects of Eyjafjallajökull Volcanic Ash on Innate Immune System Responses and Bacterial Growth in Vitro. ''Environmental Health Perspectives'', ''121''(6), 691–698. https://doi.org/10.1289/ehp.1206004.

Shezi, B., Mathee, A., Cele, N., Ndabandaba, S., & Street, R. A. (2020). Occupational Exposure to Fine Particulate Matter (PM4 and PM2.5) during Hand-Made Cookware Operation: Personal, Indoor and Outdoor Levels. International journal of environmental research and public health, 17(20), 7522. <nowiki>https://doi.org/10.3390/ijerph17207522</nowiki>

Stewart, C., Johnston, D. M., Leonard, G. S., Horwell, C. J., Thordarson, T., & Cronin, S. J. (2006). ''Contamination of water supplies by volcanic ashfall: A literature review and simple impact modelling.''

U.S. Geological Survey. (n.d.). ''Volcanic ash impacts & mitigation: Eyes and skin''. U.S. Department of the Interior. <nowiki>https://volcanoes.usgs.gov/volcanic_ash/eye_skin.html</nowiki>

U.S. Geological Survey. (2023). ''1980 Cataclysmic Eruption''. Retrieved from <nowiki>https://www.usgs.gov/volcanoes/mount-st.-helens/science/1980-cataclysmic-eruption</nowiki>

‌

‌{{Projectbox_EOSC311}}
[[Category:EOSC311]]

File:VolcanoImage.jpg

2026-06-18T02:43:19Z

RAJMEHRA: Uploaded a work by U.S. Geological Survey from https://www.usgs.gov/media/images/illustration-basic-process-magma-formation-movement-s with UploadWizard

=={{int:filedesc}}==
{{Information
|description={{en|1=Volcano}}
|date=2026-06-17
|source=https://www.usgs.gov/media/images/illustration-basic-process-magma-formation-movement-s
|author=U.S. Geological Survey
|permission=
|other versions=
}}

=={{int:license-header}}==
{{cc-by-sa-4.0}}

Course:EOSC311/2026/Volcanic Ash Composition and its effects on Human Health and Microbial Ecosystems

2026-06-18T02:33:13Z

RAJMEHRA: no image

== Introduction ==
Volcanic eruptions are mighty natural forces that are able to cause vast changes in ecosystems and the atmosphere. Volcanoes, when they erupt, release large amounts of volcanic ash, volcanic gases, and fragments of rocks that are able to be spread over long distances through many mediums like wind and water, affecting not only local but also global scales. Most of the time, volcanoes are talked about from a geological perspective, but the impacts of volcanoes go beyond simple things like land creation. Volcanic emissions can have an influence on air, water, and soil quality that can have an impact on both human health and the microbial ecosystem. This project looks at the connections between volcanic geology, human health and microbiology by exploring how volcanic ash materials have an impact on respiratory and immune systems, as well as microbial ecosystems.

==Volcanic Ash Composition==

=== 2.1 Formation of Volcanic Ash ===
Magma is molten rock found beneath the Earth's surface that contains dissolved gases, including water vapor, carbon dioxide (CO₂), and sulfur dioxide (SO₂). As magma rises toward the surface, pressure decreases, causing these gases to escape and form bubbles known as vesicles, similar to how a carbonated drink fizzes when opened. When magma rises quickly, pressure builds up inside these bubbles until they burst, breaking the magma into fine particles known as volcanic ash (Durant et al., 2010). The composition of the magma affects how explosive the eruption is — magmas with high silica content tend to erupt more explosively, producing larger amounts of ash.
=== 2.2 Particle Size and Structure ===
During an explosive volcanic eruption, rocks, mineral fragments, and/or ash are ejected into the air; these are known as pyroclasts. Volcanic ash is defined as pyroclasts with a diameter of 2mm or less, an important factor in determining how hazardous the ash is to human health. The size is measured using aerodynamic diameter, and particles are classified into two key health-relevant categories: thoracic particles (PM10), which are less than 10 μm in diameter, and respirable particles (PM4), which are less than 4 μm in diameter (Horwell & Baxter, 2006). The percentage of respirable material in ash varies considerably depending on the volcano, the explosivity of the eruption, and the distance from the vent at which ash is collected (Horwell & Baxter, 2006).

Fine ash particles tend to fall in loose clusters of less than 100 μm, which break apart easily when they hit the ground or when they get disturbed by external factors, such as wind, passing vehicles, or everyday human activity (Horwell & Baxter, 2006). This means that ash that has already settled on the ground can be lifted back into the air and inhaled all over again, making exposure an ongoing cycle even after an eruption has ended. The irregular shape of these particles also makes them more physically damaging once inhaled, as their sharp edges can irritate and damage the lining of the airways (Horwell & Baxter, 2006). Together, these structural properties, combined with how small respirable particles are, make volcanic ash particularly harmful to the respiratory system.

=== 2.3 Chemical and Mineral Composition ===
Volcanic ash is not made up from a single uniform material; its chemical and mineral composition varies depending on the type of magma that erupted and the nature of the eruption. Ash is made up of three main components: glass, which is a quenched (rapidly cooled) melt; lithic fragments, which are pieces of pre-existing rock from the volcanic vent; and crystals, which are minerals that formed within the magma before the eruption (Durant et al., 2010). The crystal component can include minerals such as quartz, feldspar, pyroxenes, amphiboles, and olivine, with the exact proportions depending on the magma composition.

One of the most important and dangerous components of volcanic ash is crystalline silica, which can appear as quartz, cristobalite, or tridymite (Horwell & Baxter, 2006). Cristobalite is considered the most toxic of these forms and is particularly common in volcanoes. It forms through a process called devitrification, the conversion of volcanic glass into crystalline material (Horwell & Baxter, 2006).

Aside from crystalline silica, volcanic ash also carries a range of trace elements and chemical species on its surface (Durant et al., 2010). During an eruption, gases such as fluorine, sulfur dioxide, and hydrogen chloride interact with ash particles, leaving chemical coatings on the surface of the ash (Durant et al., 2010). These surface chemicals can be rapidly released when ash comes into contact with water, contaminating water supplies and soil environments. The presence of iron on ash surfaces is also significant, as it can generate harmful free radicals when it interacts with the lung, potentially causing cell damage even in ash that contains little to no crystalline silica (Horwell & Baxter, 2006).

== Notable Volcanic Eruptions ==

=== 3.1 Mount St. Helens ===
[[File:Vhp img571.jpg|thumb|Mout St. Helens eruption on May 18, 1980, showing the volcanic ash plume produced during the eruption. Source: U.S. Geological Survey (Public Domain).]]
The eruption of Mount St. Helen in Washington, USA, on May 19, 1980, is considered one of the most significant volcanic eruptions in modern history. Following a magnitude 5.1 earthquake, the volcano experienced a lateral blast that destroyed large areas surrounding the mountain. The eruption produced approximately 540 million tons of volcanic ash, which spread across much of the United States and even circled the globe within weeks. The eruption produced a large ash cloud that caused transportation disruptions, environmental damage, and respiratory health concerns (U.S. Geological Survey [USGS], 2023). The event demonstrated how volcanic ash can affect areas far beyond the immediate vicinity of a volcano and remains an important case study for volcanic hazard research.

=== 3.2 Comparison of Major Ash- Producing Eruption ===
Several volcanic eruptions have produced significant amounts of ash, including Mount St. Helens (1980), Mount Pinatubo (1991), and Eyjafjallajökull (2010). While Mount St. Helens caused major regional impacts, Mount Pinatubo had global climate effects due to the large volume of ash and gas released into the atmosphere. In contrast Eyjafjallajökull primarily disrupted air travel across Europe. These eruptions highlight the diverse environmental health and economic impacts that volcanic ash can produce (Newhall & Punongbayan, 1997).

== Effects on Human Health ==

=== 4.1 Respiratory Effects ===
The respiratory systems are direct targets for volcanic ash due to the ease of inhalation of these tiny particles and their sheer abundance when released. Respirable particles are of greatest concern. These respirable particles, due to their size of around 1/20th the width of a human hair, are capable of being suspended in the air for an extensive amount of time (Shezi et al., 2020). Because of this size, they are fine enough to penetrate deep into the alveolar region of the lungs, where they have the greatest toxic potential (Horwell & Baxter, 2006).

Once these particles reach these alveloar regions, they interact with the cells of the immune system. Resident macrophages and mast cells act as the first line of defense, the primary response, to the inhaled particles. These immune cells are working hard, engulfing these particles, in a process named phagocytosis. The issue is that, when volcanoes release volcanic ash, it does not release only a few particles. The large quantities of ash that are present in the air after an eruption, and the amount of particles inhaled at once, make it difficult for macrophages and mast cells to remove all of them. Due to this, there is a release of cytokines that aim to recruit other immune cells to initiate the second line of defense, but this results in '''something''' inflammation. This inflammatory response that occurs leads to unwanted effects of swelling or irritation in the lungs that causes coughing or shortness of breath (Horwell & Baxter, 2006).

In addition to these respirable particles, exposure to crystalline silica has been studied throughout occupational medicine and has been determined as a cause of silicosis, a serious fibrotic lung disease, and prolonged exposure may also increase the risk of lung cancer (Horwell & Baxter, 2006). This makes the crystalline silica content of ash one of the most critical factors in assessing its health hazard. Repeated exposure to these particles (like seen in people from these volcanic regions that we mentioned above?) can cause chronic respiratory damage.

=== 4.2 Eye and Skin Irritation ===
Volcanic ash also has the ability to impact the eyes and skin. Volcanic ash frequently contains sharp objects that are able to scratch sensitive surfaces when they come into contact. The eyes being exposed to these volcanic ash particles is said to cause unfavourable symptoms like corneal abrasions or scratches, which can cause severe eye pain, conjunctivitis, and more. The skin is also another surface that volcanic ash can attack. When ash comes into contact with the skin, it can cause irritation and reddening of the skin (U.S. Geological Survey).

=== 4.3 Immune Systems ===
The impacts of volcanic ash exposure are noticeable on both the respiratory and eye and skin levels. But the impacts of volcanic ash are able to go beyond and are shown to damage the immune system as a whole. As mentioned before, the primary and secondary responses are how the body is able to fight off bacteria that manage to enter to prevent infections from occurring. What is interesting is that it has been shown that the properties of volcanic ash may play a role in interfering with these systems (Monick et al., 2013).

Macrophages, the first line of defense, play a role in engulfing foreign particles in a process named phagocytosis. Research shows that volcanic ash is actually able to impair macrophages from performing their task, resulting in a reduced ability to remove these foreign particles (Monick et al., 2013). This reduced ability allows for more particles to be present in the body, increasing the chances of infection and other negative effects.

With volcanic ash carrying a range of trace elements like iron, it can actually provide a source of nutrients that bacteria can use to grow and survive inside the body (Monick et al., 2013).

== Effects on Microbial Ecosystem ==

=== 5.1 Soil Microbial Communities ===
Volcanic ash can significantly affect soil microbial communities by altering soil chemistry, pH, moisture retention, and nutrient availability. Immediately after an eruption, thick layer of ash may reduce microbial activity by covering existing soil and limiting access to oxygen and different organic matter. As a result, the abundance and diversity of microorganisms often decrease in the short term (Fiantis et al., 2019).

However, volcanic ash also contains minerals such as iron, magnesium, potassium, and phosphorus that can gradually improve soil fertility. As weathering occurs, these nutrients are released into the soil and become available to microorganisms. Certain bacteria and fungi are able to colonize newly formed volcanic deposits and play an important role in breaking down minerals, cycling nutrients, and supporting soil development. Over time, microbial communities help create conditions that allow plants and other organisms to establish themselves, contributing to ecosystem recovery (Fiantis et al., 2019).

Volcanic ash can have both positive and negative impacts on soil microbial ecosystems, depending on whether the effects are considered in the short term or the long term.

=== 5.2 Water Contamination ===
Volcanic ash can enter rivers, lakes and ground water through rainfall. Ash particles may increase water turbidity and alter water chemistry, affecting microorganisms that live in aquatic environments. Also, high concentrations of ash can reduce light penetration and sirupt microbial processes that are important for maintaining water quality and ecosystem health (Stewart et al, 2006).

Furthermore, volcanic ash may change the chemical composition of water by releasing minerals and other substances. These changes can alter the balance of microbial communities, causing some species to decline while others become more abundant. As a result normal nutrient cycling and other ecological processes carried out by microorganisms may be disrupted until the ecosystem gradually recovers (Stewart et al., 2006).

=== 5.3 Recovery and Adaptation ===
Although volcanic eruptions can initially disrupt microbial ecosystems, many microorganisms are capable of adapting to the new environmental conditions. Over time, microbial communities recolonize ash- covered areas and contribute to soil formation and nutrient cycling. This recovery process helps establish conditions that support plant growth and the gradual restoration of affected ecosystems (Fiantis et al., 2019).

== Interconnections Between Human Health and Microbial Ecosystem ==

When volcanic ash is deposited onto soil and water environments, it does not settle as an inert layer. Instead, it restructures the chemical and biological conditions of the microbial communities in that area. Ash alters the carbon and nitrogen concentrations in the soil, changes the pH, and introduces new minerals and trace elements, thereby affecting which microorganisms survive and thrive (Maltz et al., 2024). Various studies were conducted following the 1980 eruption of Mount St. Helens. These studies showed that microbial communities remained fundamentally restructured for decades, with bacterial and fungal composition varying significantly with ashfall intensity and soil chemistry (Maltz et al., 2024). Along with these studies, research on volcanic ash fertilization was also being conducted. These studies showed that once ash concentrations pass a certain threshold, the soil microbiome shifts. Some bacteria that may help plants grow actually increase, while others decline. This suggests ash doesn't just kill off microbial life, it reorganizes it in complex ways (Staudigel et al., 2025). These shifts matter because soil microorganisms are responsible for nearly all biogeochemical transformations, including nutrient cycling, soil formation, and organic matter decomposition, meaning that disruptions to microbial communities have cascading effects on the broader ecosystem (Staudigel et al., 2025).

These environmental changes caused by ashfall do not stay contained in the soil. They also extend into water systems, such as rivers, lakes, and reservoirs, and ultimately reach human homes and human systems. When ash falls into water supplies, it increases acidity and releases soluble contaminants, including fluoride, iron, sulphate, and chloride, into drinking water (Stewart et al., 2006). It also increases turbidity, which is dangerous because the ash particles present interfere with the disinfection process, allowing harmful bacteria to survive in the water (Stewart et al., 2006). This raises the risk of waterborne disease outbreaks (Stewart et al., 2006). Aside from water contamination, the restructuring of soil microbial communities also affects food systems. Changes in soil chemistry disrupt nutrient cycling, which reduces soil fertility and can lower crop yields. On top of this, volcanic air pollution has been linked to respiratory illness, cardiovascular effects, and increased healthcare visits in exposed populations (Stewart et al., 2022). This shows that the path from environmental disruption to human health outcomes works through several pathways at once, not just one (Stewart et al., 2022). Together, these interconnections show that the health impacts of volcanic ash cannot be understood by looking at geology, microbiology, or human health on their own; they are fundamentally linked.

== Conclusions ==

==References==
<references />
Baxter, P. J., Ing, R., Falk, H., & Plikaytis, B. (1983). Mount St. Helens eruptions: The acute respiratory effects of volcanic ash in a North American community. Archives of Environmental Health, 38(3), 138–143. https://doi.org/10.1080/00039896.1983.10543892

Durant, A. J., Bonadonna, C., & Horwell, C. J. (2010). Atmospheric and Environmental Impacts of Volcanic Particulates. Elements, 6(4), 235–240. https://doi.org/10.2113/gselements.6.4.235

Fiantis, D., Ginting, F. I., Gusnidar, G., Nelson, M., & Van Ranst, E. (2019). ''Volcanic ash, soil formation, and ecosystem development.''

Horwell, C. J., & Baxter, P. J. (2006). The respiratory health hazards of volcanic ash: a review for volcanic risk mitigation. Bulletin of Volcanology, 69(1), 1–24. https://doi.org/10.1007/s00445-006-0052-y

Newhall, C. G., & Punongbayan, R. S. (1997). ''The cataclysmic 1991 eruption of Mount Pinatubo, Philippines''. U.S. Geological Survey Fact Sheet 113-97.

Maltz, M.R., Allen, M.F., Phillips, M.L., Hernandez, R.R., Shulman, H.B., Freund, L., Andrews, L.V., Botthoff, J.K., and Aronson, E.L. (2024). Microbial community structure in recovering forests of Mount St. Helens. Frontiers in Microbiomes, 3, 1399416. https://doi.org/10.3389/frmbi.2024.1399416

Monick, M. M., Baltrusaitis, J., Powers, L. S., Borcherding, J. A., Caraballo, J. C., Mudunkotuwa, I., Peate, D. W., Walters, K., Thompson, J. M., Grassian, V. H., Gudmundsson, G., & Comellas, A. P. (2013). Effects of Eyjafjallajökull Volcanic Ash on Innate Immune System Responses and Bacterial Growth in Vitro. ''Environmental Health Perspectives'', ''121''(6), 691–698. https://doi.org/10.1289/ehp.1206004.

Shezi, B., Mathee, A., Cele, N., Ndabandaba, S., & Street, R. A. (2020). Occupational Exposure to Fine Particulate Matter (PM4 and PM2.5) during Hand-Made Cookware Operation: Personal, Indoor and Outdoor Levels. International journal of environmental research and public health, 17(20), 7522. <nowiki>https://doi.org/10.3390/ijerph17207522</nowiki>

Stewart, C., Johnston, D. M., Leonard, G. S., Horwell, C. J., Thordarson, T., & Cronin, S. J. (2006). ''Contamination of water supplies by volcanic ashfall: A literature review and simple impact modelling.''

U.S. Geological Survey. (n.d.). ''Volcanic ash impacts & mitigation: Eyes and skin''. U.S. Department of the Interior. <nowiki>https://volcanoes.usgs.gov/volcanic_ash/eye_skin.html</nowiki>

U.S. Geological Survey. (2023). ''1980 Cataclysmic Eruption''. Retrieved from <nowiki>https://www.usgs.gov/volcanoes/mount-st.-helens/science/1980-cataclysmic-eruption</nowiki>

‌

‌{{Projectbox_EOSC311}}
[[Category:EOSC311]]

Course:EOSC311/2026/Volcanic Ash Composition and its effects on Human Health and Microbial Ecosystems

2026-06-18T02:32:53Z

RAJMEHRA: image

== Introduction ==
Volcanic eruptions are mighty natural forces that are able to cause vast changes in ecosystems and the atmosphere. Volcanoes, when they erupt, release large amounts of volcanic ash, volcanic gases, and fragments of rocks that are able to be spread over long distances through many mediums like wind and water, affecting not only local but also global scales. Most of the time, volcanoes are talked about from a geological perspective, but the impacts of volcanoes go beyond simple things like land creation. Volcanic emissions can have an influence on air, water, and soil quality that can have an impact on both human health and the microbial ecosystem. This project looks at the connections between volcanic geology, human health and microbiology by exploring how volcanic ash materials have an impact on respiratory and immune systems, as well as microbial ecosystems.

==Volcanic Ash Composition==

=== 2.1 Formation of Volcanic Ash ===
Magma is molten rock found beneath the Earth's surface that contains dissolved gases, including water vapor, carbon dioxide (CO₂), and sulfur dioxide (SO₂). As magma rises toward the surface, pressure decreases, causing these gases to escape and form bubbles known as vesicles, similar to how a carbonated drink fizzes when opened. When magma rises quickly, pressure builds up inside these bubbles until they burst, breaking the magma into fine particles known as volcanic ash (Durant et al., 2010). The composition of the magma affects how explosive the eruption is — magmas with high silica content tend to erupt more explosively, producing larger amounts of ash.
[[File:Volcano1762026.png|thumb|The process by which magma ascends from Earth's mantle and erupts at the surface. Source: Source: U.S. Geological Survey (Public Domain).]]

=== 2.2 Particle Size and Structure ===
During an explosive volcanic eruption, rocks, mineral fragments, and/or ash are ejected into the air; these are known as pyroclasts. Volcanic ash is defined as pyroclasts with a diameter of 2mm or less, an important factor in determining how hazardous the ash is to human health. The size is measured using aerodynamic diameter, and particles are classified into two key health-relevant categories: thoracic particles (PM10), which are less than 10 μm in diameter, and respirable particles (PM4), which are less than 4 μm in diameter (Horwell & Baxter, 2006). The percentage of respirable material in ash varies considerably depending on the volcano, the explosivity of the eruption, and the distance from the vent at which ash is collected (Horwell & Baxter, 2006).

Fine ash particles tend to fall in loose clusters of less than 100 μm, which break apart easily when they hit the ground or when they get disturbed by external factors, such as wind, passing vehicles, or everyday human activity (Horwell & Baxter, 2006). This means that ash that has already settled on the ground can be lifted back into the air and inhaled all over again, making exposure an ongoing cycle even after an eruption has ended. The irregular shape of these particles also makes them more physically damaging once inhaled, as their sharp edges can irritate and damage the lining of the airways (Horwell & Baxter, 2006). Together, these structural properties, combined with how small respirable particles are, make volcanic ash particularly harmful to the respiratory system.

=== 2.3 Chemical and Mineral Composition ===
Volcanic ash is not made up from a single uniform material; its chemical and mineral composition varies depending on the type of magma that erupted and the nature of the eruption. Ash is made up of three main components: glass, which is a quenched (rapidly cooled) melt; lithic fragments, which are pieces of pre-existing rock from the volcanic vent; and crystals, which are minerals that formed within the magma before the eruption (Durant et al., 2010). The crystal component can include minerals such as quartz, feldspar, pyroxenes, amphiboles, and olivine, with the exact proportions depending on the magma composition.

One of the most important and dangerous components of volcanic ash is crystalline silica, which can appear as quartz, cristobalite, or tridymite (Horwell & Baxter, 2006). Cristobalite is considered the most toxic of these forms and is particularly common in volcanoes. It forms through a process called devitrification, the conversion of volcanic glass into crystalline material (Horwell & Baxter, 2006).

Aside from crystalline silica, volcanic ash also carries a range of trace elements and chemical species on its surface (Durant et al., 2010). During an eruption, gases such as fluorine, sulfur dioxide, and hydrogen chloride interact with ash particles, leaving chemical coatings on the surface of the ash (Durant et al., 2010). These surface chemicals can be rapidly released when ash comes into contact with water, contaminating water supplies and soil environments. The presence of iron on ash surfaces is also significant, as it can generate harmful free radicals when it interacts with the lung, potentially causing cell damage even in ash that contains little to no crystalline silica (Horwell & Baxter, 2006).

== Notable Volcanic Eruptions ==

=== 3.1 Mount St. Helens ===
[[File:Vhp img571.jpg|thumb|Mout St. Helens eruption on May 18, 1980, showing the volcanic ash plume produced during the eruption. Source: U.S. Geological Survey (Public Domain).]]
The eruption of Mount St. Helen in Washington, USA, on May 19, 1980, is considered one of the most significant volcanic eruptions in modern history. Following a magnitude 5.1 earthquake, the volcano experienced a lateral blast that destroyed large areas surrounding the mountain. The eruption produced approximately 540 million tons of volcanic ash, which spread across much of the United States and even circled the globe within weeks. The eruption produced a large ash cloud that caused transportation disruptions, environmental damage, and respiratory health concerns (U.S. Geological Survey [USGS], 2023). The event demonstrated how volcanic ash can affect areas far beyond the immediate vicinity of a volcano and remains an important case study for volcanic hazard research.

=== 3.2 Comparison of Major Ash- Producing Eruption ===
Several volcanic eruptions have produced significant amounts of ash, including Mount St. Helens (1980), Mount Pinatubo (1991), and Eyjafjallajökull (2010). While Mount St. Helens caused major regional impacts, Mount Pinatubo had global climate effects due to the large volume of ash and gas released into the atmosphere. In contrast Eyjafjallajökull primarily disrupted air travel across Europe. These eruptions highlight the diverse environmental health and economic impacts that volcanic ash can produce (Newhall & Punongbayan, 1997).

== Effects on Human Health ==

=== 4.1 Respiratory Effects ===
The respiratory systems are direct targets for volcanic ash due to the ease of inhalation of these tiny particles and their sheer abundance when released. Respirable particles are of greatest concern. These respirable particles, due to their size of around 1/20th the width of a human hair, are capable of being suspended in the air for an extensive amount of time (Shezi et al., 2020). Because of this size, they are fine enough to penetrate deep into the alveolar region of the lungs, where they have the greatest toxic potential (Horwell & Baxter, 2006).

Once these particles reach these alveloar regions, they interact with the cells of the immune system. Resident macrophages and mast cells act as the first line of defense, the primary response, to the inhaled particles. These immune cells are working hard, engulfing these particles, in a process named phagocytosis. The issue is that, when volcanoes release volcanic ash, it does not release only a few particles. The large quantities of ash that are present in the air after an eruption, and the amount of particles inhaled at once, make it difficult for macrophages and mast cells to remove all of them. Due to this, there is a release of cytokines that aim to recruit other immune cells to initiate the second line of defense, but this results in '''something''' inflammation. This inflammatory response that occurs leads to unwanted effects of swelling or irritation in the lungs that causes coughing or shortness of breath (Horwell & Baxter, 2006).

In addition to these respirable particles, exposure to crystalline silica has been studied throughout occupational medicine and has been determined as a cause of silicosis, a serious fibrotic lung disease, and prolonged exposure may also increase the risk of lung cancer (Horwell & Baxter, 2006). This makes the crystalline silica content of ash one of the most critical factors in assessing its health hazard. Repeated exposure to these particles (like seen in people from these volcanic regions that we mentioned above?) can cause chronic respiratory damage.

=== 4.2 Eye and Skin Irritation ===
Volcanic ash also has the ability to impact the eyes and skin. Volcanic ash frequently contains sharp objects that are able to scratch sensitive surfaces when they come into contact. The eyes being exposed to these volcanic ash particles is said to cause unfavourable symptoms like corneal abrasions or scratches, which can cause severe eye pain, conjunctivitis, and more. The skin is also another surface that volcanic ash can attack. When ash comes into contact with the skin, it can cause irritation and reddening of the skin (U.S. Geological Survey).

=== 4.3 Immune Systems ===
The impacts of volcanic ash exposure are noticeable on both the respiratory and eye and skin levels. But the impacts of volcanic ash are able to go beyond and are shown to damage the immune system as a whole. As mentioned before, the primary and secondary responses are how the body is able to fight off bacteria that manage to enter to prevent infections from occurring. What is interesting is that it has been shown that the properties of volcanic ash may play a role in interfering with these systems (Monick et al., 2013).

Macrophages, the first line of defense, play a role in engulfing foreign particles in a process named phagocytosis. Research shows that volcanic ash is actually able to impair macrophages from performing their task, resulting in a reduced ability to remove these foreign particles (Monick et al., 2013). This reduced ability allows for more particles to be present in the body, increasing the chances of infection and other negative effects.

With volcanic ash carrying a range of trace elements like iron, it can actually provide a source of nutrients that bacteria can use to grow and survive inside the body (Monick et al., 2013).

== Effects on Microbial Ecosystem ==

=== 5.1 Soil Microbial Communities ===
Volcanic ash can significantly affect soil microbial communities by altering soil chemistry, pH, moisture retention, and nutrient availability. Immediately after an eruption, thick layer of ash may reduce microbial activity by covering existing soil and limiting access to oxygen and different organic matter. As a result, the abundance and diversity of microorganisms often decrease in the short term (Fiantis et al., 2019).

However, volcanic ash also contains minerals such as iron, magnesium, potassium, and phosphorus that can gradually improve soil fertility. As weathering occurs, these nutrients are released into the soil and become available to microorganisms. Certain bacteria and fungi are able to colonize newly formed volcanic deposits and play an important role in breaking down minerals, cycling nutrients, and supporting soil development. Over time, microbial communities help create conditions that allow plants and other organisms to establish themselves, contributing to ecosystem recovery (Fiantis et al., 2019).

Volcanic ash can have both positive and negative impacts on soil microbial ecosystems, depending on whether the effects are considered in the short term or the long term.

=== 5.2 Water Contamination ===
Volcanic ash can enter rivers, lakes and ground water through rainfall. Ash particles may increase water turbidity and alter water chemistry, affecting microorganisms that live in aquatic environments. Also, high concentrations of ash can reduce light penetration and sirupt microbial processes that are important for maintaining water quality and ecosystem health (Stewart et al, 2006).

Furthermore, volcanic ash may change the chemical composition of water by releasing minerals and other substances. These changes can alter the balance of microbial communities, causing some species to decline while others become more abundant. As a result normal nutrient cycling and other ecological processes carried out by microorganisms may be disrupted until the ecosystem gradually recovers (Stewart et al., 2006).

=== 5.3 Recovery and Adaptation ===
Although volcanic eruptions can initially disrupt microbial ecosystems, many microorganisms are capable of adapting to the new environmental conditions. Over time, microbial communities recolonize ash- covered areas and contribute to soil formation and nutrient cycling. This recovery process helps establish conditions that support plant growth and the gradual restoration of affected ecosystems (Fiantis et al., 2019).

== Interconnections Between Human Health and Microbial Ecosystem ==

When volcanic ash is deposited onto soil and water environments, it does not settle as an inert layer. Instead, it restructures the chemical and biological conditions of the microbial communities in that area. Ash alters the carbon and nitrogen concentrations in the soil, changes the pH, and introduces new minerals and trace elements, thereby affecting which microorganisms survive and thrive (Maltz et al., 2024). Various studies were conducted following the 1980 eruption of Mount St. Helens. These studies showed that microbial communities remained fundamentally restructured for decades, with bacterial and fungal composition varying significantly with ashfall intensity and soil chemistry (Maltz et al., 2024). Along with these studies, research on volcanic ash fertilization was also being conducted. These studies showed that once ash concentrations pass a certain threshold, the soil microbiome shifts. Some bacteria that may help plants grow actually increase, while others decline. This suggests ash doesn't just kill off microbial life, it reorganizes it in complex ways (Staudigel et al., 2025). These shifts matter because soil microorganisms are responsible for nearly all biogeochemical transformations, including nutrient cycling, soil formation, and organic matter decomposition, meaning that disruptions to microbial communities have cascading effects on the broader ecosystem (Staudigel et al., 2025).

These environmental changes caused by ashfall do not stay contained in the soil. They also extend into water systems, such as rivers, lakes, and reservoirs, and ultimately reach human homes and human systems. When ash falls into water supplies, it increases acidity and releases soluble contaminants, including fluoride, iron, sulphate, and chloride, into drinking water (Stewart et al., 2006). It also increases turbidity, which is dangerous because the ash particles present interfere with the disinfection process, allowing harmful bacteria to survive in the water (Stewart et al., 2006). This raises the risk of waterborne disease outbreaks (Stewart et al., 2006). Aside from water contamination, the restructuring of soil microbial communities also affects food systems. Changes in soil chemistry disrupt nutrient cycling, which reduces soil fertility and can lower crop yields. On top of this, volcanic air pollution has been linked to respiratory illness, cardiovascular effects, and increased healthcare visits in exposed populations (Stewart et al., 2022). This shows that the path from environmental disruption to human health outcomes works through several pathways at once, not just one (Stewart et al., 2022). Together, these interconnections show that the health impacts of volcanic ash cannot be understood by looking at geology, microbiology, or human health on their own; they are fundamentally linked.

== Conclusions ==

==References==
<references />
Baxter, P. J., Ing, R., Falk, H., & Plikaytis, B. (1983). Mount St. Helens eruptions: The acute respiratory effects of volcanic ash in a North American community. Archives of Environmental Health, 38(3), 138–143. https://doi.org/10.1080/00039896.1983.10543892

Durant, A. J., Bonadonna, C., & Horwell, C. J. (2010). Atmospheric and Environmental Impacts of Volcanic Particulates. Elements, 6(4), 235–240. https://doi.org/10.2113/gselements.6.4.235

Fiantis, D., Ginting, F. I., Gusnidar, G., Nelson, M., & Van Ranst, E. (2019). ''Volcanic ash, soil formation, and ecosystem development.''

Horwell, C. J., & Baxter, P. J. (2006). The respiratory health hazards of volcanic ash: a review for volcanic risk mitigation. Bulletin of Volcanology, 69(1), 1–24. https://doi.org/10.1007/s00445-006-0052-y

Newhall, C. G., & Punongbayan, R. S. (1997). ''The cataclysmic 1991 eruption of Mount Pinatubo, Philippines''. U.S. Geological Survey Fact Sheet 113-97.

Maltz, M.R., Allen, M.F., Phillips, M.L., Hernandez, R.R., Shulman, H.B., Freund, L., Andrews, L.V., Botthoff, J.K., and Aronson, E.L. (2024). Microbial community structure in recovering forests of Mount St. Helens. Frontiers in Microbiomes, 3, 1399416. https://doi.org/10.3389/frmbi.2024.1399416

Monick, M. M., Baltrusaitis, J., Powers, L. S., Borcherding, J. A., Caraballo, J. C., Mudunkotuwa, I., Peate, D. W., Walters, K., Thompson, J. M., Grassian, V. H., Gudmundsson, G., & Comellas, A. P. (2013). Effects of Eyjafjallajökull Volcanic Ash on Innate Immune System Responses and Bacterial Growth in Vitro. ''Environmental Health Perspectives'', ''121''(6), 691–698. https://doi.org/10.1289/ehp.1206004.

Shezi, B., Mathee, A., Cele, N., Ndabandaba, S., & Street, R. A. (2020). Occupational Exposure to Fine Particulate Matter (PM4 and PM2.5) during Hand-Made Cookware Operation: Personal, Indoor and Outdoor Levels. International journal of environmental research and public health, 17(20), 7522. <nowiki>https://doi.org/10.3390/ijerph17207522</nowiki>

Stewart, C., Johnston, D. M., Leonard, G. S., Horwell, C. J., Thordarson, T., & Cronin, S. J. (2006). ''Contamination of water supplies by volcanic ashfall: A literature review and simple impact modelling.''

U.S. Geological Survey. (n.d.). ''Volcanic ash impacts & mitigation: Eyes and skin''. U.S. Department of the Interior. <nowiki>https://volcanoes.usgs.gov/volcanic_ash/eye_skin.html</nowiki>

U.S. Geological Survey. (2023). ''1980 Cataclysmic Eruption''. Retrieved from <nowiki>https://www.usgs.gov/volcanoes/mount-st.-helens/science/1980-cataclysmic-eruption</nowiki>

‌

‌{{Projectbox_EOSC311}}
[[Category:EOSC311]]

File:Volcano1762026.png

2026-06-18T02:31:26Z

RAJMEHRA: Uploaded a work by U.S. Geological Survey from https://www.usgs.gov/media/images/illustration-basic-process-magma-formation-movement-s with UploadWizard

Course:EOSC311/2026/Volcanic Ash Composition and its effects on Human Health and Microbial Ecosystems

2026-06-16T02:11:18Z

RAJMEHRA: 4.3

Course:EOSC311/2026/Volcanic Ash Composition and its effects on Human Health and Microbial Ecosystems

2026-06-16T01:50:24Z

RAJMEHRA: /* 4.2 Eye and Skin Irritation */

Course:EOSC311/2026/Volcanic Ash Composition and its effects on Human Health and Microbial Ecosystems

2026-06-14T00:55:10Z

RAJMEHRA: /* 4.1 Respiratory Effects */