Chapter 17 Human Health and Environmental Risks

1. Chapter 17 Human Health and Environmental Risks

2. Three categories of human health risks • Physical – excessive exposure to UV radiation or radon • Biological - associated with disease • Chemical – naturally occurring as well as synthetically produced

3. Leading causes of death in the world

4. Biological Risks • Infectious diseases- those caused by infectious agents, known as pathogens. • Chronic disease- slowly impairs the functioning of a person’s body. • Acute disease- rapidly impairs the functioning of a person’s body. • Epidemic – rapid increase • Pandemic – epidemic over a large geographic area

5. Leading Health Risks

6. Historical Diseases • Plague – aka bubonic plague or black death • Caused by bacteria spread by fleas • Most recent pandemic in Asia in early 1900’s • Malaria • Caused by a parasitic protist carried by mosquitoes • Tuberculosis • Caused by airborne bacteria • Serious problem today is drug-resistant strains

7. Emergent Diseases • HIV/AIDS – spread by contact with infected bodily fluids • Ebola – extremely high death rate • Mad Cow Disease – caused by prions; spread to humans through ingestion of infected meat • Bird Flu – aka H1N1; spread from infected domesticated birds • West Nile Virus – spread from wild birds to humans via mosquitoes

8. Transmission of pathogens

9. Chemical Risks • Neurotoxins- chemicals that disrupt the nervous system – some insecticides, lead, mercury • Carcinogens- chemicals that cause cancer – asbestos, radon, formaldehyde, tobacco • Teratogens- chemicals that interfere with the normal development of embryos or fetuses – thalidomide, alcohol • Allergens- chemicals that cause allergic reactions – peanuts, milk, penicillin, codeine • Endocrine disruptors- chemicals that interfere with the normal functioning of hormones in an animal’s body - hormones

10. Dose-Response Studies • LD50- lethal dose that kills 50% of the individuals • Studies are conducted on animals and extrapolated to humans • ED50- effective dose that causes 50% of the animals to display the harmful but nonlethal effect • Sublethal effects – is the chemical a teratogen, carcinogen, neurotoxin?

11. LD50 Study

12. Synergistic interactions- when two risks come together and cause more harm that one would. • Example: the health impact of a carcinogen such as asbestos can be much higher if an individual also smokes tobacco.

13. Routes of Chemical Exposure

14. Bioaccumulation • An increased concentration of a chemical within an organism over time • Usually occurs with fat-soluble substances • Classic example: DDT

15. Biomagnification in the food chain - DDT

16. Persistence • How long a chemical remains in the environment

17. Risk Analysis

18. Probability of death in U.S.

19. Qualitative Risk Assessment • Making a judgment of the relative risks of various decisions • Probability- the statistical likelihood of an event occurring and the probability of that event causing harm

20. Quantitative Risk Assessment • The approach to conducting a quantitative risk assessment is: • Risk= probability of being exposed to a hazard X probability of being harmed if exposed

21. Stockholm Convention • In 2001, a group of 127 nations gathered in Stockholm, Sweden, to reach an agreement on restricting the global use of some chemicals • 12 chemicals were to be banned, phased out, or reduced • These include DDT, PCBs, and certain chemicals that are by-products of manufacturing processes.