Chapter 18

1. Chapter 18 Environmental Hazards and Human Health

2. RISKS AND HAZARDS • Risk is a measure of the likelihood that you will suffer harm from a hazard. • We can suffer from: • Biological hazards: from more than 1,400 pathogens. • Chemical hazards: in air, water, soil, and food. • Physical hazards: fire, earthquake, volcanic eruption… • Cultural hazards: smoking, poor diet, unsafe sex, drugs, unsafe working conditions, and poverty.

3. BIOLOGICAL HAZARDS: DISEASE IN DEVELOPED AND DEVELOPING COUNTRIES • Transmissible or infectious • Diseases caused by living organisms • bacteria • viruses • Spread from person to person • Nontransmissible disease • Diseases not caused by living organisms • Cannot spread from one person to another

4. HIV/AIDS Epidemic • 2005 about 42 million people worldwide (1.1 million in the U.S.) were infected with HIV (WHO) • No vaccine and no cure for HIV • Drugs help some infected people live longer, but only a fraction can afford them.

5. The Global HIV/AIDS Epidemic • AIDS has reduced the life expectancy of sub-Saharan Africa from 62 to 47 years – 40 years in the seven countries most severely affected by AIDS. • Virus itself is not deadly • cripples the immune system • Kaposi’s sarcoma (right) Projected age structure of Botswana's population in 2020. Figure 18-2

6. Transmissible Disease • Pathway for infectious disease in humans. Figure 18-4

7. Transmissible Disease • WHO estimates that each year the world’s seven deadliest infections kill 13.6 million people – most of them the poor in developing countries. Figure 18-5

8. Growing Germ Resistance to Antibiotics • Rapidly reproducing, infectious bacteria are becoming genetically resistant to widely used antibiotics • Genetic resistance - overuse of antibiotics selects cells that are resistant • These reproduce and resistant populations result • Pesticide resistant vectors - overuse of pesticides which produce pesticide resistant insects that carry bacteria and viruses

9. Example: The Growing Global Threat from Tuberculosis • The highly infectious tuberculosis (TB) kills 1.7 million people per year and could kill 25 million people 2020. • Recent increases in TB are due to: • Lack of TB screening and control programs especially in developing countries due to expenses. • Genetic resistance to the most effective antibiotics.

10. Viral Diseases • Flu, HIV, and hepatitis B viruses infect and kill many more people each year than highly publicized West Nile and SARS viruses. • The influenza virus is the biggest killer virus worldwide. • Pigs, chickens, ducks, and geese are the major reservoirs of flu • Moves from one species to another mutating as it goes

11. Viral Diseases • HIV is the second biggest killer virus worldwide. Five major priorities to slow the spread of the disease are: • Prevent further spread. • Concentrate on “at risk” groups • Free HIV testing and pressure people to get tested. • Educational programs. • Free/low-cost drugs to slow disease progress.

12. Malaria – Death by Mosquito • Malaria kills about 2 million people per year and has probably killed more than all of the wars ever fought. Figure 18-7

13. Malaria – Death by Mosquito • Estimated that spending $2-3 billion on malaria treatment may save more than 1 million lives per year. • Spraying DDT inside homes greatly reduces the number of malaria cases. • Under international treaty enacted in 2002, DDT is being phased out in developing countries. Figure 18-6

14. CHEMICAL HAZARDS • A toxic chemical can cause temporary or permanent harm or death. • Mutagens are chemicals or forms of radiation that cause or increase the frequency of mutations in DNA. • Teratogens are chemicals that cause harm or birth defects to a fetus or embryo. • Carcinogens are chemicals or types of radiation that can cause or promote cancer.

15. CHEMICAL HAZARDS • A hazardous chemical can harm humans or other animals because it: • Is flammable • Is explosive • An irritant • Interferes with oxygen uptake • Induce allergic reactions.

16. Effects of Chemicals on the Immune, Nervous, and Endocrine Systems • Long-term exposure to some chemicals at low doses may disrupt the body’s: • Immune system: specialized cells and tissues that protect the body against disease and harmful substances. • Nervous system: brain, spinal cord, and peripheral nerves. • Endocrine system: complex network of glands that release minute amounts of hormones into the bloodstream.

17. Effects of Chemicals on the Immune, Nervous, and Endocrine Systems • Molecules of certain synthetic chemicals have shapes similar to those of natural hormones and can adversely affect the endocrine system. Figure 18-9

18. A Black Day in Bhopal, India • The world’s worst industrial accident occurred in 1984 at a pesticide plant in Bhopal, India. • Explosion at Union Carbide pesticide plant in an underground storage tank • released highly toxic methyl isocyanate (MIC) gas. • 15,000-22,000 people died • Indian officials claim that simple upgrades could have prevented the tragedy.

19. TOXICOLOGY: ASSESSING CHEMICAL HAZARDS • Factors determining the harm caused by exposure to a chemical include: • The amount of exposure (dose). • The frequency of exposure. • The person who is exposed. • The effectiveness of the body’s detoxification systems. • One’s genetic makeup.

20. TOXICOLOGY: ASSESSING CHEMICAL HAZARDS • Typical variations in sensitivity to a toxic chemical within a population, mostly because of genetic variation. Figure 18-10

21. TOXICOLOGY: ASSESSING CHEMICAL HAZARDS • Estimating human exposure to chemicals and their effects is very difficult because of the many and often poorly understood variables involved. Figure 18-11

22. TOXICOLOGY: ASSESSING CHEMICAL HAZARDS • Children are more susceptible to the effects of toxic substances because: • Children breathe more air, drink more water, and eat more food per unit of body weight than adults. • They are exposed to toxins when they put their fingers or other objects in their mouths. • Children usually have less well-developed immune systems and detoxification processes than adults.

23. TOXICOLOGY: ASSESSING CHEMICAL HAZARDS • Under existing laws, most chemicals are considered innocent until proven guilty, and estimating their toxicity is difficult, uncertain, and expensive. • Federal and state governments do not regulate about 99.5% of the commercially used chemicals in the U.S.

24. Protecting Children from Toxic Chemicals • The U.S. Environmental Protection Agency proposed that regulators should assume children have 10 X the exposure risk of adults to cancer-causing chemicals. • Some health scientists suggest we should assume a risk 100 X that of adults.

25. RISK ANALYSIS • Scientists have developed ways to evaluate and compare risks, decide how much risk is acceptable, and find affordable ways to reduce it. Figure 18-12

26. RISK ANALYSIS • Estimating risks from using many technologies is difficult due to unpredictability of human behavior, chance, and sabotage. • Reliability of a system is multiplicative: • If a nuclear power plant is 95% reliable and human reliability is 75%, then the overall reliability is (0.95 X 0.75 = 0.71) 71%.

27. RISK ANALYSIS • Annual deaths in the U.S. from tobacco use and other causes in 2003. Figure 18-A

28. RISK ANALYSIS • Number of deaths per year in the world from various causes. Parentheses show deaths in terms of the number of fully loaded 400-passenger jumbo jets crashing every day of the year with no survivors. Figure 18-13

29. Perceiving Risk • Most individuals evaluate the relative risk they face based on: • Degree of control. • Fear of unknown. • Whether we voluntarily take the risk. • Whether risk is catastrophic. • Unfair distribution of risk. • Sometimes misleading information, denial, and irrational fears can cloud judgment.

30. RISK ANALYSIS • Comparisons of risks people face expressed in terms of shorter average life span. Figure 18-14