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.