1. Environmental Hazards and Human Health
Chapter 18
Environmental Hazards and Human Health

2. Chapter Overview Questions
What types of hazards do people face?
What types of disease (biological hazards) threaten people in developing countries and developed countries?
What chemical hazards do people face?
How can risks be estimated and recognized?

3. Updates Online
The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at to access InfoTrac articles.
InfoTrac: Report Shows 2005 to Be 'Least Bad Year' of AIDS Epidemic. Lawrence K. Altman. The New York Times, May 31, 2006 pA6(L).
InfoTrac: Concern Grows Over Increase In Diabetes Around World. Marc Santora. The New York Times, June 11, 2006 pA27(L).
InfoTrac: Push for New Tactics as War on Malaria Falters. Celia W. Dugger. The New York Times, June 28, 2006 pA1(L).
The National Academies: Genetically Altered Bacteria Could Block Malaria Transmission
Science Daily: Study Shows Promise For Simplified Treatment Of HIV Infection
The Gates Foundation

4. Core Case Study: The Global HIV/AIDS Epidemic
According to the World Health Organization (WHO), in 2005 about 42 million people worldwide (1.1 million in the U.S.) were infected with HIV.
There is no vaccine for HIV – if you get AIDS, you will eventually die from it.
Drugs help some infected people live longer, but only a tiny fraction can afford them.

5. Core Case Study: 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.
Projected age structure of Botswana's population in 2020.
Figure 18-2

6. Core Case Study: The Global HIV/AIDS Epidemic
The virus itself is not deadly, but it cripples the immune system, leaving the body susceptible to infections such as Kaposi’s sarcoma (above).
Figure 18-1

7. 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: such as fire, earthquake, volcanic eruption…
Cultural hazards: such as smoking, poor diet, unsafe sex, drugs, unsafe working conditions, and poverty.

8. BIOLOGICAL HAZARDS: DISEASE IN DEVELOPED AND DEVELOPING COUNTRIES
Diseases not caused by living organisms cannot spread from one person to another (nontransmissible disease), while those caused by living organisms such as bacteria and viruses can spread from person to person (transmissible or infectious)

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

10. Wild animals Livestock Mosquitoes Food Water Pets Air Fetus and babies
Figure 18.4
Science: pathways for infectious disease in humans.
Fetus and babies
Other humans
Humans
Fig. 18-4, p. 420

11. 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

12. Disease (type of agent) Deaths per year
Pneumonia and flu (bacteria and viruses)
3.2 million
HIV/AIDS (virus)
3.0 million
Malaria (protozoa)
2.0 million
Diarrheal diseases (bacteria and viruses)
1.9 million
Figure 18.5
Global outlook: the World Health Organization estimates that each year the world’s seven deadliest infectious diseases kill 13.6 million people—most of them poor people in developing countries. This amounts to about 37,300 mostly preventable deaths every day. QUESTION: What three things would you do to reduce this death toll? (Data from the World Health Organization)
Tuberculosis (bacteria)
1.7 million
Hepatitis B (virus)
1 million
Measles (virus)
800,000
Fig. 18-5, p. 420

13. Case Study: Growing Germ Resistance to Antibiotics
Rabidly producing infectious bacteria are becoming genetically resistant to widely used antibiotics due to:
Genetic resistance: Spread of bacteria around the globe by humans, overuse of pesticides which produce pesticide resistant insects that carry bacteria.
Overuse of antibiotics: A 2000 study found that half of the antibiotics used to treat humans were prescribed unnecessarily.

14. Case Study: 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.

15. Viral Diseases
Flu, HIV, and hepatitis B viruses infect and kill many more people each year then 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. As they move from one species to another, they can mutate and exchange genetic material with other viruses.

16. Viral Diseases
HIV is the second biggest killer virus worldwide. Five major priorities to slow the spread of the disease are:
Quickly reduce the number of new infections to prevent further spread.
Concentrate on groups in a society that are likely to spread the disease.
Provide free HIV testing and pressure people to get tested.
Implement educational programs.
Provide free or low-cost drugs to slow disease progress.

17. How Would You Vote?
To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living in the Environment.
Should developed and developing nations mount an urgent global campaign to reduce the spread of HIV and to help countries afflicted by the disease?
a. No. A global AIDS campaign could divert attention and resources from efforts to combat other serious threats.
b. Yes. The disease is decimating the populations and destroying the economies of many developing countries.

18. Case Study: 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

19. Plasmodium develop in mosquito
Female mosquito bites infected human, ingesting blood that contains Plasmodium gametocytes
Merozoites enter bloodstream and develop into gametocytes causing malaria and making infected person a new reservoir
Plasmodium develop in mosquito
Figure 18.7
Science: the life cycle of malaria. Plasmodium parasites circulate from mosquito to human and back to mosquito.
Sporozoites penetrate liver and develop into merozoites
Female mosquito injects Plasmodium sporozoites into human host.
Fig. 18-7, p. 423

20. Stepped Art Female mosquito bites infected human,
ingesting blood that contains Plasmodium
gametocytes
Merozoites enter blood-stream and develop into gametocytes causing malaria and making
infected person a new reservoir
Plasmodium
develops in
mosquito
Sporozoites penetrate liver
and develop into merozoites
Female mosquito injects Plasmodium sporozoites into human host
Stepped Art
Fig. 18-7, p. 423

21. Case Study: Malaria – Death by Mosquito
Economists estimate that spending $2-3 billion on malaria treatment may save more than 1 million lives per year.
Figure 18-6

22. Case Study: Malaria – Death by Mosquito
Spraying insides of homes with low concentrations of the pesticide DDT greatly reduces the number of malaria cases.
Under international treaty enacted in 2002, DDT is being phased out in developing countries.

23. Solutions Infectious Diseases
Increase research on tropical diseases and vaccines
Reduce poverty
Decrease malnutrition
Improve drinking water quality
Reduce unnecessary use of antibiotics
Educate people to take all of an antibiotic prescription
Reduce antibiotic use to promote livestock growth
Figure 18.8
Solutions: ways to prevent or reduce the incidence of infectious diseases, especially in developing countries. QUESTION: Which three of these approaches do you think are the most important?
Careful hand washing by all medical personnel
Immunize children against major viral diseases
Oral rehydration for diarrhea victims
Global campaign to reduce HIV/AIDS
Fig. 18-8, p. 424

24. Ecological Medicine and Infectious Diseases
Mostly because of human activities, infectious diseases are moving at increasing rates from one animal species to another (including humans).
Ecological (or conservation) medicine is devoted to tracking down these connections between wildlife and humans to determine ways to slow and prevent disease spread.

25. 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.

26. 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.

27. 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.

28. 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

29. Normal Hormone Process Hormone Mimic Hormone Blocker Hormone
Estrogenlike chemical
Antiandrogen chemical
Receptor
Cell
Figure 18.9
Science: hormones are molecules that act as messengers in the endocrine system to regulate various bodily processes, including reproduction, growth, and development. Each type of hormone has a unique molecular shape that allows it to attach to specially shaped receptors on the surface of, or inside, cells and to transmit its chemical message (left). Molecules of certain pesticides and other synthetic chemicals have shapes similar to those of natural hormones and can affect the endocrine system in people and various other animals. These molecules are called hormonally active agents (HAAs). Because of the difficulty in determining the harmful effects of long-term exposure to low levels of HAAs, there is uncertainty about their effects on human health.
Fig. 18-9, p. 427

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

31. 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.

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

33. Very sensitive Very insensitive
Number of individuals affected
Very sensitive
Majority of population
Very insensitive
Figure 18.10
Science: typical variations in sensitivity to a toxic chemical within a population, mostly because of differences in genetic makeup. Some individuals in a population are very sensitive to small doses of a toxin (left), and others are very insensitive (right). Most people fall between these two extremes (middle). QUESTION: Approximately where do you fall on this curve for most chemicals?
Dose (hypothetical units)
Fig , p. 430

34. 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

35. Water pollutant levels
Air pollutant levels
Soil/dust levels
Food pesticide levels
Nutritional health ?
Mathematical measurements & modeling
Overall health
Lifestyle
Figure 18.11
Science: estimating human exposure to chemicals and their effects is very difficult because of the many and often poorly understood variables involved. QUESTION: Which three of these factors do you think make you more vulnerable to the harmful effects of chemicals?
Predicted level of toxicant in people
Personal habits
Metabolism
Genetic predisposition
Accumulation
Excretion
Lung, intestine & skin absorption rates
Fig , p. 431

36. 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.

37. 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.

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

39. TOXICOLOGY: ASSESSING CHEMICAL HAZARDS
Some scientists and health officials say that preliminary but not conclusive evidence that a chemical causes significant harm should spur preventive action (precautionary principle).
Manufacturers contend that wide-spread application of the precautionary principle would make it too expensive to introduce new chemicals and technologies.

40. How Would You Vote?
To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living in the Environment.
Should we rely more on the precautionary principle as a way to reduce the risks from chemicals and technologies?
a. No. Assuming that every chemical or technology is a serious health or environmental threat will lead to wasteful over-regulation, high costs and hinder the development of critically needed pesticides, plastics, and other commercial products.
b. Yes. Preventing the commercialization of harmful chemicals and technologies is better than dealing with the high costs of medical treatments and environmental damage.

41. 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

42. Comparative Risk Analysis Most Serious Ecological and Health Problems
High-Risk Health Problems • Indoor air pollution • Outdoor air pollution • Worker chemical exposure
• Pollutants in drinking water • Pesticide residues on food • Toxic chemicals in consumer products
High-Risk Ecological Problems • Global climate change • Stratospheric ozone depletion • Wildlife habitat alteration & destruction • Species extinction, loss of biodiversity
Medium-Risk Ecological Problems • Acid deposition • Pesticides • Airborne toxic chemicals • Toxic chemicals, nutrients, and sediment in surface waters
Figure 18.12
Science: comparative risk analysis of the most serious ecological and health problems according to scientists acting as advisers to the EPA. Risks under each category are not listed in rank order. QUESTION: Which two risks in each of the high-risk problems do you think are the most serious? (Data from Science Advisory Board, Reducing Risks, Washington, D.C.: Environmental Protection Agency, 1990)
Low-Risk Ecological Problems • Oil spills • Groundwater pollution • Radioactive isotopes • Acid runoff to surface waters • Thermal pollution
Fig , p. 433

43. 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%.

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

45. Cause of Death Deaths 442,000 Tobacco use 101,500 (43,450 auto)
Accidents
85,000
Alcohol use
75,000 (16,000 from AIDS)
Infectious diseases
Pollutants/toxins
55,000
Figure 18.A
Annual deaths in the United States from tobacco use and other causes in Smoking is by far the nation’s leading cause of preventable death, causing more premature deaths each year than all the other categories in this figure combined. (Data from U.S. National Center for Health Statistics and Centers for Disease Control and Prevention and U.S. Surgeon General)
30,600
Suicides
20,622
Homicides
17,000
Illegal drug use
Fig. 18-A, p. 435

46. 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

47. Cause of death Annual deaths 11 million (75) 5 million (34)
Poverty/malnutrition/ disease cycle
Tobacco
5 million (34)
Pneumonia and flu
3.2 million (22)
Air pollution
3 million (21)
HIV/AIDS
3 million (21)
Malaria
2 million (14)
Diarrhea
1.9 million (13)
Tuberculosis
1.7 million (12)
Figure 18.13
Global outlook: number of deaths per year in the world from various causes. Numbers in parentheses give these deaths in terms of the number of fully loaded 400-passenger jumbo jets crashing every day of the year with no survivors. Because of sensational media coverage, most people have a distorted view of the largest annual causes of death. QUESTION: Which three of these items are most likely to shorten your life span? (Data from World Health Organization)
Car accidents
1.2 million (8)
Work-related injury & disease
1.1 million (8)
Hepatitis B
1 million (7)
Measles
800,000 (5)
Fig , p. 435

48. 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.

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

50. Shortens average life span in the U.S. by
Hazard
Shortens average life span in the U.S. by
Poverty
7–10 years
Born male
7.5 years
Smoking
6–10 years
Overweight (35%)
6 years
Unmarried
5 years
Overweight (15%)
2 years
Spouse smoking
1 year
Driving
7 months
Air pollution
5 months
Alcohol
5 months
Drug abuse
4 months
Flu
4 months
AIDS
3 months
Drowning
1 month
Pesticides
1 month
Figure 18.14
Global outlook: comparison of risks people face, expressed in terms of shorter average life span. After poverty and gender, the greatest risks people face come mostly from the lifestyle choices they make. These are merely generalized relative estimates. Individual responses to these risks can differ because of factors such as genetic variation, family medical history, emotional makeup, stress, and social ties and support. QUESTION: Which three of these items are most likely to shorten your life span? (Data from Bernard L. Cohen)
Fire
1 month
Natural radiation
8 days
Medical X rays
5 days
Oral contraceptives
5 days
Toxic waste
4 days
Flying
1 day
Hurricanes, tornadoes
1 day
Lifetime near nuclear plant
10 hours
Fig , p. 436

51. Becoming Better at Risk Analysis
We can carefully evaluate or tune out of the barrage of bad news covered in the media, compare risks, and concentrate on reducing personal risks over which we have some control.
Figure 18-3

52. Hazard identification Comparative risk analysis
Risk Assessment
Risk Management
Hazard identification
Comparative risk analysis
What is the hazard?
How does it compare with other risks?
Risk reduction
How much should it be reduced?
Probability of risk
How likely is the event?
Risk reduction strategy
How will the risk be reduced?
Figure 18.3
Science: risk assessment and risk management.
Consequences of risk
Financial commitment
What is the likely damage?
How much money should be spent?
Fig. 18-3, p. 419