Chapter 18

Environmental Hazards and Human

Health

Amazon Crude - CBS News Video

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 Projected age structure of Botswana's population of Botswana's population in 2020.in 2020. Figure 18-2Figure 18-2

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 18-1Figure 18-1

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.

Transmissible Disease

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

Fig. 18-4, p. 420

PetsLivestock

Wild animals Mosquitoes Food Water

Air

Fetus and babies

Other humans Humans

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 18-5Figure 18-5

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.

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.

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.

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 18-7Figure 18-7

Fig. 18-7, p. 423

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

Sporozoites penetrate liver and develop into merozoites

Female mosquito injects Plasmodium sporozoites into human host.

• 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.

Case Study: Malaria – Death by Mosquito

Fig. 18-8, p. 424

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

Careful hand washing by all medical personnel

Immunize children against major viral diseases

Oral rehydration for diarrhea victims

Global campaign to reduce HIV/AIDS

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.

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.

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 18-9Figure 18-9

Fig. 18-9, p. 427

Hormone Estrogenlike chemical

Antiandrogen chemical

Receptor

Normal Hormone Process Hormone Mimic Hormone Blocker

Cell

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.

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.

Dose-response curve w/ LD-50

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.

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.

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 18-12Figure 18-12

Fig. 18-12, p. 433

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

Low-Risk Ecological Problems • Oil spills • Groundwater pollution • Radioactive isotopes • Acid runoff to surface waters • Thermal pollution

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%.

RISK ANALYSIS

• Annual deaths in the U.S. from tobacco use and other causes in 2003.

Figure 18-AFigure 18-A

Fig. 18-A, p. 435

Cause of Death Deaths

Tobacco use442,000

Accidents101,500 (43,450 auto)

Alcohol use85,000

Infectious diseases

75,000 (16,000 from AIDS)

Pollutants/toxins

55,000

Suicides30,600

Homicides20,622

Illegal drug use

17,000

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 18-13Figure 18-13

Fig. 18-13, p. 435

Cause of death Annual deaths

Poverty/malnutrition/

disease cycle

11 million (75)

Tobacco 5 million (34)

Pneumonia and flu 3.2 million (22)

Air pollution 3 million (21)

HIV/AIDS

Malaria 2 million (14)

Diarrhea 1.9 million (13)

Tuberculosis 1.7 million (12)

Car accidents 1.2 million (8)Work-related injury

& disease 1.1 million (8)

Hepatitis B 1 million (7)

Measles 800,000 (5)

3 million (21)

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.

RISK ANALYSIS

• Comparisons of risks people face expressed in terms of shorter average life span.

Figure 18-14Figure 18-14

Fig. 18-14, p. 436

Shortens average life span in the U.S. byHazard

PovertyBorn male

SmokingOverweight (35%)

Unmarried 5 yearsOverweight (15%) 2 yearsSpouse smoking 1 year

Driving 7 monthsAir pollution 5 months

Alcohol 5 monthsDrug abuse 4 months

Flu 4 monthsAIDS 3 months

Drowning 1 monthPesticides 1 month

Fire 1 monthNatural radiation 8 days

Medical X rays 5 daysOral contraceptives 5 days

Toxic waste 4 daysFlying 1 day

Hurricanes, tornadoes 1 dayLifetime near nuclear plant 10 hours

6 years6–10 years

7.5 years7–10 years

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 18-3Figure 18-3

Fig. 18-3, p. 419

Risk Assessment Risk Management

Hazard identification Comparative risk analysis

What is the hazard? How does it compare with other risks?

How much should it be reduced?

Risk reduction

Probability of risk

How likely is the event? Risk reduction strategy

How will the risk be reduced?

Consequences of risk Financial commitment

What is the likely damage?

How much money should be spent?