Course:CONS200/2023/The Environmental Impacts of Sunscreen on Hawaii’s Coral Reefs

Background

Healthy Coral Reef

Coral Reefs

Coral reefs are underwater ecosystems that are comprised of coral skeletons that have been deposited over time. They are made of coral polyps, which are organisms that have a fixed base, a tubelike body, and tentacles for catching prey, that secrete calcium carbonate beneath their bodies creating a foundation for young coral to settle upon. Additionally, algae, seaweed, sponges, and other species contribute to creating coral reefs by adding foundations for new coral to develop. Coral reefs are often located primarily in the tropics near the equator where waters are warmer, as they have a narrow temperature range of 20°C to 23°C (73°F to 84°F). Coral reefs also require clear and shallow waters and usually do not grow in depths over 46 meters or in waters with sediments, chemical, or nutrient pollution as they interfere with the physiological processes required for coral survival.

Ecological Relevance

Coral reefs are among the most biodiverse ecosystems on the planet, providing habitats for a vast array of marine life, including fish, sea turtles, and invertebrates. High biodiversity within coral reefs allows for these ecosystems to be resilient in regard to both disturbances and environmental changes. Coral reefs offer significant coastal protection against waves and flooding. With increased storm abundance and flooding potential occurring due to climate change coastal communities have begun to rely on coral reefs to decrease these natural disturbances. Coral is also fundamental on a social level as it stimulates the local economies through tourism and fishing as well as acts as an essential food source and resource for Hawaiian communities. Coral reefs are incredibly sensitive to environmental changes and disturbances. Coral reef populations are threatened by global climate change and human pollution, including chemical pollution caused by sunscreen. Climate change causes increases in ocean temperatures which results in coral bleaching events and higher disease rates.

Contamination

OB-3 (Oxybenzone)

Coral Bleaching Phenomenon, often the result of over-exposure to OB-3 Contaminants

Oxybenzone (OB-3), is a common ingredient found in sunscreens, with the purpose of protecting wearer’s against UV light. In recent years, OB-3 is emerging as a contaminant of concern in marine environments. As a photo-toxicant, the negative effects are more pronounced in the light, however, in a study investigating effect of OB-3 on coral, the coral was left in a deformed, sessile condition after exposure in both the light and the darkness.

Each year, between 6,000 and 14,000 tons of sunscreen, most of which contain OB-3, are estimated to be released into coral reefs. Approximately 14,000 tons of sunscreen are estimated to be released into coral reefs annually, with up to 10% composed of OB-3. This puts at least 10% of global reefs at risk and about 40% of coastal reefs at risk of exposure.

Exposure to OB-3 chemicals resulted in changes in morphology in coral planulae. Healthy coral have an elongated “cucumber-like” morphology, and in the study by Downs et al. in 2018, the control group exhibited this healthy morphology. Within the first 4 hours of exposure, the planulae displayed a significant reduction in ciliary movement and the morphology was that of a deformed “dewdrop.” After 8 hours of OB-3 exposure, a complete reduction of movement was observed, with planulae becoming deformed and taking on a white opaque coloration. In other words, after 8 hours of exposure to OB-3, coral planulae were bleaching, a process that means the coral lose their symbiotic dinoflagellate zooxanthellae and photosynthetic pigments. Furthermore, exposure of coral planulae to OB-3 may result in an increased sensitivity to temperature stress, resulting in bleaching at a lower temperature than unexposed corals. Coral cells were found to be more sensitive than planulae across many concentrations of OB-3 making cell mortality a potential indicator of reproductive failures.

In addition to being a photo-toxicant, OB-3 is a genotoxicant meaning exposure can cause alterations at a genetic level. A positive relationship between DNA-AP lesions and oxybenzone concentration has been determined.

Over-Tourism

Tourism as a Source of Contamination

Unsustainable tourism practices (tourism degrading primary natural resources) are a prominent source of OB-3 contamination. Areas of high ecological sensitivity tend to witness increased tourism intensity, with UV filter contamination being commonly observed as “sunscreen sheens” on the surface of water bodies. Economic incentives of maintaining high tourism rates of these areas are unmistakable, with coral reefs responsible for approximately 36 billion dollars of revenue in 2017 in the U.S.A. Alongside the United States numbers, the United Nations Tourism Organization estimated a figure of 1.3 billion tourists visiting “coastal attractions” in 2017, with this figure expected to exceed 1.8 billion by 2030. While unsustainable tourism and over-tourism provide exceptional short term economic incentives, the long term effects of these industries will lead to a loss of tourism, economic value, and tax revenue. Tourists partaking in recreational swimming and beach activities often apply UV protectants, as advised by the U.S. Food and Drug Administration. It is recommended to apply approximately 36g of sun-protectant every 90 minutes, resulting in significant discharge of sunscreen, particularly in highly populated tourist destinations. Levels of OB-3 contamination display seasonal variation, with concentrations exceeding a 25% increase in the summer season, suggesting a link between human recreational activities and contamination of water bodies.

Wastewater Treatment

Wastewater treatment plants, a crucial aspect in municipal water recycling, demonstrate difficulty in treating OB-3 chemicals. Studies conducted in Korea, China, the United States, Japan, and Thailand all attest to this, displaying detectable levels of OB-3 in raw and treated water. A notable property of UV filters is a low solubility in water, preventing OB-3 from being successfully removed during the treatment process. With such low treatability, it is not puzzling that OB-3 contaminants have been observed not only within natural water sources, but chlorinated sources such as public pools. This contamination of controlled water sources poses its own risk, as these UV filters react with chlorinated water creating hazardous byproducts known as brominated transformation products. Thus, wastewater treatment plants have shown little effectiveness in sufficiently treating water contaminated with OB-3.

Hanauma Bay

Context

Map of Oahu, Hanauma Bay located in bottom right

Hanauma Bay, Oahu, is Hawaii’s most popular swimming destination. With annual visitors ranging from 2.8 - 3.5 million between 1980 and 2010, the bay saw an average of 3,000 - 4,000 visitors daily, peaking at 10,000-13,000. Prohibiting visitors from visiting for the period of March 2020 - December 2020, the park re-opened in 2021 permitting no more than 1000 visitors per day. Designated as Hawaii’s first Marine Life Conservation District in 1967,and located within the U.S. Hawaiian Islands Humpback Whale National Marine Sanctuary, Hanauma Bay is a critical coral reef habitat. Classified as Class AA waters under Hawaii’s Clean Water Act,Hanauma Bay’s water must “remain in their natural pristine state as nearly as possible with an absolute minimum of pollution or alteration of water quality from any human-caused source or actions.”

Case Study

Tourists swimming in Hanauma Bay

Hanauma Bay is a prime example of OB-3 contamination. Of 10 sampling locations within Hanauma Bay, OB-3 was detected in 100% of water samples. These contaminants may remain present within the bay for up to 50 hours following a single exposure event.

While a threat is posed by active swimmers, sunscreen not expelled during swimming may also contaminate the bay’s water due to beach showers,rainfall run-off, and surprisingly marine plastic debris. OB-3’s induction of an increased sensitivity to heat stress commonly results in a bleaching response below commonly recorded temperatures. Below the normal bleaching temperature of 30.3 °C,Hanauma Bay showcased bleaching at temperatures of 29.8 °C in 2015. These measurements were not isolated to Hanauma Bay, as other tourism-intense coastlines observe elevated bleaching. One coral species of note, P. damicornis, is an organism of abundance in fringing reef areas of Hawaii. This presence is expected to be notable in high numbers within Hanauma Bay, however, both formal and impromptu surveys conclude the species may be extinct within the bay.  

Hawaii's Climate

Hawaii’s seasonal climate plays a role in contamination events as well. Conditions in May-August pose a dry climate, with only 0.5cm of precipitation monthly. Following this season, September through November introduce the rainy season, with precipitation increasing to 1.25cm in November. This dry season causes an accumulation of contaminants in sands in proximity to beach showers. September showcases the highest concentration of contaminants, aligning with the period of highest observation of bleaching in coral. November exhibited the lowest concentration of contaminants, matched with a lower tourism rate and increased water flow due to increased precipitation.

Proposed Questions

These results have posed multiple questions to researchers. Discourse surrounding the proposal of bay closures have arisen, with questions arising regarding closure lengths and the amount of time required to ensure contaminants do not reach a hazardous level. The concept of intermittent closures was proposed; the idea of the bay closing regularly to prevent increased exposure to OB-3. This method of intermittent closure could be designed to align with periods of low oceanic flushing and water exchange. Human safety within Hanauma Bay has been acknowledged as an area that must be researched further, with unanswered questions surrounding the detrimental effects of contaminated water. Studies dating back to the 20th century describe the ability of OB-3 and adjacent benzophenones to absorb through human skin, remaining at notable levels for up to 2 weeks post exposure. The effects on both embryonic and larval fish development are a main note of concern for researchers studying Hanauma Bay, with the question of OB-3’s impact on the health of pregnant individuals and children partaking in recreational activities within Hanauma Bay.

Social Concern

The contamination of coral reefs by sunscreen chemicals has become a public concern and advocacy groups have called for increased regulation of sunscreen products to protect coral reef ecosystems. In response, Hawaii has implemented a ban on the sale of sunscreen products containing OB-3 and octinoxate. Other regions and countries, such as the US Virgin Islands and Palau, have also implemented similar bans.

Social Awareness

Although Hawaii has implemented a ban on sunscreens containing OB-3 the extensive tourist populations on the islands result in substantial rates of internationally bought sunscreen use. As most of the sunscreens used by tourists are not bought on the island they are not subject to the ban and thus often contain OB-3. A study conducted in 2020 found that 75% of users on Oahu and Hawaii Island were aware of the risks of OB-3 on coral reefs over 60% still participated in the use of sunscreens that contained these chemicals.

Although the sunscreen ban has reduced the use of chemical sunscreen containing OB-3 it has not eliminated their use. Therefore, additional measures are needed to better control the use of these sunscreens. One proposed idea is to increase the labeling standards on sunscreens and at beaches. This would allow consumers the opportunity and knowledge to change their sunscreen choices to become better for the coral reefs.

Policy

Hawaii made history by passing Senate Bill No. 2571 in 2018, coming into effect in 2021, becoming the first U.S. state to ban the sale and distribution of sunscreens containing the chemicals OB-3 and octinoxate, which have been found to be harmful to coral reefs and marine ecosystems. This move was met with mixed reactions, with some advocating for reef-safe sunscreen ingredients, while others expressed concerns about the potential impact on public health and sunscreen efficacy. Its synonyms include benzophenone-3, Escalol 567, Eusolex 4360, KAHSCREEN BZ-3, and Uvasorb MET/C. Under Senate Bill No. 2571, "SPF sunscreen protection personal care products" include lotion, paste, salve, ointment, cream, solid stick applicator, brush applicator, roll-on applicator, aerosol spray, non-aerosol spray pump, and automated and manual mist spray. Additionally, the prohibition has prompted discussions of similar legislation in other regions with fragile coral reef ecosystems.

The ban on OB-3 and octinoxate in sunscreen products is an important step toward protecting coral reef ecosystems. However, further research and policy action may be necessary to address the broader issue of contaminants in coral reef ecosystems and their impact on marine life.

It is demonstrated the deleterious effects of OB-3 on coral planulae and primordial cells grown in culture. Significant concentrations of OB-3 were detected in the water of Hawaii and the U.S. Virgin Islands, indicating the pervasive prevalence of this toxic chemical. Another study revealed that sunscreens containing these compounds cause coral bleaching by promoting viral infections in coral reefs.

NOAA also acknowledged the danger that sunscreen chemicals pose to coral reefs. In their report, they cited studies indicating that OB-3 and octinoxate can deform coral larvae, rendering them incapable of swimming, settling, or forming new colonies. This disruption to the coral reefs' life cycle causes a decline in their overall health and resilience.

Conclusion

Coral Reefs are an integral part of marine ecosystems and are facing severe ecological impacts due to exposure to OB-3, a chemical present in common sunscreen products. Repeated exposure to OB-3 chemicals poses a threat to ecological integrity of Hawaiian Coral Reefs. This contamination stems from the use of topical sunscreens and other personal care products worn by tourists and swimmers containing OB-3. OB-3 causes significant damage to coral, specifically juvenile, causing bleaching, increased temperature sensitivity, reproductive damage, and impacts to mobility. In addition to exposure from swimmers, sunscreen has entered marine ecosystems through beach showers, rain run-off, and wastewater. In accordance with rising social concern promoted by advocacy groups, Hawaii passed Senate Bill No. 2571, prohibiting the sale of products containing OB-3 from 2021 onwards. Sunscreen pollution poses a significant threat to Hawaii's coral reefs, which are already under pressure from climate change and other stressors. While the issue has gained attention in recent years, more research is needed to fully understand the extent of the problem and identify effective solutions that balance environmental and public health concerns.