1. Toxicology please grab a notes sheet

2. Toxicology: the study of the adverse effects of chemicals on health. Toxicity: how harmful something is. Depends on: Dose: the amount of a potentially harmful substance that is ingested, inhaled, or absorbed through the skin Frequency : how often you are exposed Genetic make up of those exposed Health of those exposed Genetic make up

3. Other factors include: Solubility (water or oil/fat) Persistence : how long the chemical remains in the environment Bioaccumulation (small dose build up in individuals over time) Biomagnification (build up as passes through food chain) Chemical interactions (antagonistic or synergistic) – Antagonistic = chemicals work against each other to lessen the effect – Synergistic = chemicals work together to intensify the effect

4. Bioaccumulation and Biomagnification Bioaccumulation results when the concentration of a chemical in specific organs or tissues is higher than would normally be expected. Biomagnification involves magnification of concentrations as they pass through the food chains and webs. The pesticide DDT becomes increasingly concentrated high in the food chain because it is stored in fatty tissue and not easily broken down or excreted.

5. Effects/Response Acute effects: immediate/rapid effect of short-term exposure. E.g. dizziness, rash, death Chronic effects: long-lasting effects from repeated exposures (sometimes from one exposure) E.g. asthma, kidney damage, heart disease

6. Should we be concerned about trace levels of toxic chemicals in the environment and our bodies? It depends on the chemical and the concentration! Most chemicals have a safe or threshold level of exposure below which their harmful effects are insignificant Our bodies have mechanisms for handing toxins – liver enzymes, cell repair mechanisms, cell regrowth

7. Example: Which are you more likely to die from?

8. Three methods of determining toxicity: 1. Case reports (usually to physicians) about health effects after exposure to a chemical; 2. epidemiology, involving studies of populations exposed to certain chemicals or diseases 3. laboratory investigations (usually with test animals); -LD 50 is the median lethal dose, the amount of a chemical received that kills 50% of animals (usually rats or mice) in a test population - poison is legally defined as a chemical that has an LD 50 of 50 milligrams or less per kilogram of body weight.

9. Not all toxins are lethal Some toxins don’t kill but still have harmfujl effects. We call these sublethal effects Instead of LD 50 we use the ED 50 (effective dose) that causes 50% of test subjects to experience the harmful effects

10. Dose–Response Curves Dose–response curves show the adverse effects of various doses of a toxic agent on a test population by plotting harmful effect as a function of dose. Threshold Level = dose where effects are first observed. No effects are seen below this level even though the subjects are exposed to the chemical. If the effect was NOT lethal, then it would be percent showing the effect (not mortality) and ED 50 (not LD 50 )

11. Chemical Hazards toxic chemicals are generally defined as substances that are fatal to over 50% of test animals at a given concentration. hazardous chemicals cause harm by -being flammable or explosive (e.g., gasoline); -irritating or damaging the skin or lungs (e.g., strong acids or alkalines such as oven cleaners); -interfering with or preventing oxygen uptake and distribution (e.g., carbon monoxide, CO); -inducing allergic reactions of the immune system (allergens).

12. mutagens are agents, chemicals and radiation, that cause mutations (changes in DNA) teratogens are agents (chemicals, radiation, or viruses) that cause birth defects; -e.g., PCBs, steroid hormones, heavy metals; alcohol, chemicals in cigarettes carcinogens are agents (chemicals, radiation, or viruses) that cause cancer (uncontrolled cell division) -over 100 types of cancer (depending on cells involved); -e.g., cigarette smoke.

13. Thalidomide- a teratogen Medication that was initially used in Europe for morning sickness/nausea in the 1950s during pregnancy because it was tested for safety in animals and showed no harm. Unfortunately thalomide caused birth defects (like shortened limbs) in tens of thousands of newborns.

14. Hormonally active agents (HAAs) aka Endocrine Disruptors Work by interfering with hormone receptors in the body: Examples: PCB’s, organophosphate pesticides, industrial solvents are known hormone mimics (frogs with extra legs, males with ovaries, etc.) Hormone Receptor Cell Normal Hormone Process Normal Mimic Hormone Blocker Estrogen- like chemicalAntiandrogen chemical

15. Neurotoxins chemicals that disrupt the nervous system in animals. Examples: insecticides interfere with insect nerve signals; also mercury, lead

16. Why Do We Know So Little about the Harmful Effects of Chemicals?  Severe limitations estimating toxicity levels and risks - we don’t usually test PEOPLE!  Acceptable levels vary between 1/100 and 1/1000 of the estimated harmful levels  10% of at least 75,000 chemicals in commercial use have been screened for toxicity  Only 2% has been tested to determine whether they are carcinogens, teratogens, or mutagens  Currently, federal and state governments do not regulate 99.5% of commercially used chemicals in the U.S.

17. the Precautionary Principle: if we don’t know whether a chemical is hazardous, then assume it is and take steps to reduce the risk  Those introducing a new chemical or new technology would have to follow new strategies A new product is considered harmful until it can be proved to be safe Existing chemicals and technologies that appear to cause significant harm must be removed Global treaty to phase out 12 most persistent pollutants detrimental to life: –DDT –Dioxin –Furans –Other persistent pesticides Treaty went into effect in 2004 and is called: Stockholm Convention on Persistent Organic Pollutants