Course:FNH200/Lessons/Lesson 12/Page 12.1

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12.1 What are Toxicants?

Terms to remember

  • Toxicants
  • Toxicity
  • Hazard
  • Risk
  • Cholinesterase inhibitors & solanine
  • Cyanogenic glycosides & amygdalin
  • Mycotoxins & aflatoxins
  • Histamine & "scombroid poisoning"
  • Saxitoxin and "paralytic shellfish poisoning"
  • Domoic acid & "amnesic shellfish poisoning'
  • Tetrodotoxin & "puffer fish poisoning"
  • Food infection, food intoxication
  • Incident & Outbreak
  • Pathogens: Escherichia coli O157:H7, Clostridium botulinum, Salmonella, Listeria monocytogenes
  • Temperature danger Zone (TDZ)

In earlier lessons, we discussed the chemical nature of foods. The chemical constituents together are responsible for the structure, texture or consistency, colour, flavour, smell and nutritional value of a food. Food may also contain other chemical entities which are less useful to us or might even pose a health risk to us. These chemicals often have a very important role in the metabolism or function of the plant or animal tissues which make up our food. It must be remembered that while we consume various plants and animal products, their structure and composition is not primarily to serve as human food, but to exist as growing and living biological entities. Some potentially harmful chemicals in these plant and animal products are said to be environmental toxicants or even contaminants. They are not normally part of the chemical mix of food for humans, but by various means have found their way into our food supply.

In order to appreciate better the role of toxicants in the safety of our food supply, it is necessary to discuss a number of concepts and define some of the terms.

  • Toxicant - a poison or a poisonous agent.
    • The term toxicant is derived from the Latin toxicum (meaning "poison") and the Greek toxikon ("arrow poison"). The term toxic conveys the meaning that something is harmful, destructive or deadly.
    • Poisons are chemicals that, in very small quantities, produce illness or death. Legally, a poison is defined as a chemical that has a lethal dose of 50 milligrams or less of chemical per kilogram of body weight.
    • Fifty mg/kg is equal to approximately three-fourths of a teaspoon for an average adult and about one-eighth of a teaspoon for an average two-year-old child (Reference: M.A. Ottoboni. 1997.The Dose Makes the Poison: A Plain Language Guide to Toxicology. 2nd edition. NewYork: Wiley)
    • When we refer to toxicants in food, we are generally referring to substances responsible for a whole spectrum of possible results, ranging from relatively minor discomfort or sickness to poisoning that can lead to death.
  • Toxicity - the intrinsic or inherent capacity of a substance to damage a biological system (produce injury) when tested by itself.
    • Substances vary in their toxicity, as reflected in their dose-response curves.
    • A toxicant can have an effect on several different functions within an individual. The individuals can vary among themselves with regard to the sensitivity of their different functions.
  • Hazard - A thing or action that can cause adverse health effects in animals (including fish), plants or humans. The capacity to produce injury under the circumstances of exposure.
    • Hazard is a much more complex concept than toxicity because it includes a consideration of conditions of use; in other words, two components are involved in assessing a hazard:
      • 1. the inherent capacity to cause harm (toxicity), and
      • 2. the ease or probability of contact between the substance and the target object.
    • These two components together describe the chance or probability that a substance will do harm. Dr. Ottoboni (cited below) provides two examples to make this clear.

"An extremely toxic chemical, such as strychnine, when sealed in an unopenable vial, can be handled freely by people with no chance that a poisoning will occur. Its toxicity has not changed, but it presents no hazard because no contact can be established between the chemical and people. Conversely, a chemical that is not highly toxic, such as boric acid, can be very hazardous when used in a manner that makes it readily available for accidental ingestion." Dr. Ottoboni

Risk - a function of the probability of an adverse health effect and the magnitude of that effect, consequential to a hazard; the likelihood of the occurrence and the magnitude of the consequences of an adverse event.