Chapter 8: Environmental Health and Toxicology

1. Chapter 8: Environmental Health and Toxicology The Environment is Out to Kill You

2. 8.1 Environmental Health • The global disease burden is changing • Infectious and emergent diseases still kill millions of people • Conservation medicine combines ecology and health care • Resistance to drugs, antibiotics, and pesticides is increasing • Who should pay for health care?

3. Pathogens • Prions (Mad Cow, Kreuzfeld-Jacob) • Viruses (Ebola, AIDS, smallpox, common cold, influenza, herpes) • Bacteria (cholera, typhoid, plague) • Protista (malaria, sleeping sickness, Giardia) • Fungi (athlete’s foot, yeast infections, Candida) • Multicellular Organisms (tapeworms, trichinosis, schistosomes)

4. Prions • Only known infectious agents without DNA • Misconfigured protein molecules • Bind to normal proteins and convert them to misconfigured form • All known prion diseases attack the brain • No known cure; invariably fatal; very nasty

5. Viruses • Viruses are non-living but reproducing • Viruses invade cells and use cell reproduction mechanisms to reproduce • Retroviruses permanently insert new DNA into cell (AIDS) • Viruses cannot be attacked in cells • Being non-living, can’t be killed by antibiotics in blood stream • Only defenses are immunization or prevention • Antibiotics do not work against viruses

6. Promiscuous Antibiotics • Used improperly against viral infections • Essentially given as placebos • Sugar pills would be more ethical • Legitimate users do not use properly • Used as prophylactic measure in factory farms • Creation of resistant micro-organisms • Waste antibiotics get into environment

7. 8.2 Toxicology • How do toxins affect us? • What Can You Do? Tips for Staying Healthy • How does diet influence health?

8. Chemical Hazards • Allergens (trigger immune response) • Neurotoxins (damage nervous system: mercury, pesticides, lead) • Mutagens (alter genes) • Teratogens (cause birth defects: alcohol, thalidomide) • Carcinogens (nickel, tobacco, radon) • Hormone mimics (PCB’s)

9. 8.3 Movement, Distribution, And Fate Of Toxins • Solubility and mobility determine where and when chemicals move • Exposure and susceptibility determine how we respond • Bioaccumulation and biomagnification increase concentrations of chemicals • Persistence makes some materials a greater threat • Chemical interactions can increase toxicity

10. 8.4 Mechanisms For Minimizing Toxic Effects • Metabolic degradation and excretion eliminate toxins • Repair mechanisms mend damage

11. 8.5 Measuring Toxicity • We usually test toxins on lab animals • “All that proves is rats shouldn’t smoke” • Reality: Animal tests predict human toxicity well • There is a wide range of toxicity • Acute and chronic doses and effects differ • Detectable levels aren’t always dangerous • With enough equipment and money, we can detect individual molecules

12. Response to Exposure

13. Response to Exposure

14. Chemicals in Concert • Antagonistic (Vitamin A, E against carcinogens) • Additive (Effects combine) • Synergistic (Effects multiply: alcohol + drugs, smoking + asbestos) • Sensitization or Desensitization

15. Factors in Toxicity • Chemical composition • Dose • Acute versus Chronic Exposure • Solubility and Mobility • Nature of exposure • Ability to metabolize, sequester, or excrete • Tendency to bioaccumulate • General Health

16. 8.6 Risk Assessment And Acceptance • Risk perception isn’t always rational • Risk acceptance depends on many factors • Some 1:1,000,000 Risks • Smoking 1.4 cigarettes (cancer, heart disease) • Two days in large city (air pollution) • 10 miles by bicycle (accident) • 1000 miles by jet (accident) • One chest X-ray (cancer) • 5 years on boundary of nuclear plant (cancer) • 100 charcoal broiled steaks (cancer)

17. Weapons of Mass Destruction • Weapons capable of inflicting large numbers of casualties or affecting a large area in a single event • Nuclear • Chemical • Biological • Any time you pack a large amount of energy into a small space, you have a potential weapon

18. Chemical Weapons • Riot Control (Tear Gas) • Choking (Cl, phosgene CCl2O) • Blood (HCN) • Nerve (Sarin) • Blister (Mustard Gas) • Hallucinogens (researched, never used) • Incapacitating (researched, never used) • Defoliants (Agent Orange, Vietnam)

19. Chemical Weapons in War • World War I • Tear Gas • Chlorine • Mustard Gas • Japanese in China: 1930's - WWII • Not used by other parties in WWII • Yemen 1960's • "Yellow Rain:" SE Asia, 1970's (Discredited) • Iraq against Kurds, Iran, 1980's • US renounced first use but reserves right to retaliate

20. Use of Chemical Weapons • Gases disperse too quickly • Usually delivered as aerosols • Dependent on weather conditions • Wind, rain, heat are unfavorable • Most historical uses against unprotected targets • Trained soldiers have protection • Reduces efficiency of both sides • Psychological effect

21. Effects of Chemical Weapons • Nerve Agents • Long Term: Nerve Disorders, Brain Damage • Blister Agents • Short Term: Severe Burns • Long Term: Skin Cancers and Lesions, Lung Damage • Most Chemical Agents Easily Decomposed • Long Term Effects of Low-Level Exposure Unknown • Gulf War Syndrome, Agent Orange

22. Biological Weapons • No known modern historical military uses • US has stated will not use • Limitations • Should be self-limiting • Need fairly quick action • Anthrax and Smallpox given most speculation • Plant pathogens • Wheat Rust, Hoof-and-Mouth • Drug Interdiction?