Chapter 11 Environmental Hazards and Human Health
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?
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. • Cultural hazards: such as smoking, poor diet, unsafe sex, drugs, unsafe working conditions, and poverty. • Physical hazards: such as fire, earthquake, volcanic eruption…
Deaths attributed to 19 leading risk factors, by country income level (2004) Source: Global Health Risk - Mortality and burden of disease attributable to selected major risks, the World Health Organisation (2009)
BIOLOGICAL HAZARDS: • nontransmissible disease • Diseases not caused by living organisms cannot spread from one person to another • Ex. Cancer, heart disease, cystic fibrosis • ~60% of deaths • transmissible or infectious • Caused by living organisms (pathogens) such as bacteria and viruses can spread from person to person • Ex. Pneumonia, HIV, Diarrhea,TB, malaria, Hep B, Measles • ~26%of deaths
Transmissible Disease • 7 Deadliest Diseases • 13.6 million people • most of them the poor in developing countries. Figure 18-5
Transmissible Disease • Pathway for infectious disease in humans. Figure 18-4
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. • 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.
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.
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.
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.
Figure 11-11Page 240 Synergy between AIDS/TB/ Malnutrition HIV/AIDS • HIV immune • suppression • facilitates active • TB development • AIDS can lead to job • loss and poverty Malnutrition TB • Malnutrition weakens • body and may • facilitate HIV • transmission • and progress • Malnutrition may • facilitate development • of active TB • TB can lead • to job loss and • malnutrition • because of • lack of money • Active TB facilitates • HIV replication • and speeds up • HIV progression
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
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
Case Study: Malaria – Death by Mosquito • 2 million people per year • probably killed more than all of the wars ever fought. Figure 18-7
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
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
Case Study: Malaria – Death by Mosquito • Low concentrations of DDT are sprayed in homes to aid in malaria prevention • Under international treaty enacted in 2002, DDT is being phased out in developing countries.
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 Fig. 18-8, p. 424
Ecological Medicine and Infectious Diseases • Human activities • infectious diseases are moving at increasing rates from one animal species to another (including humans). • Ecological (or conservation) medicine • devoted to tracking down connections between wildlife and humans • determine ways to slow and prevent disease spread.
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.
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.
Effects of Chemicals 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 18-9
Normal Hormone Process Hormone Mimic Hormone Blocker Antiandrogen chemical Estrogenlike chemical Hormone Receptor Cell Fig. 18-9, p. 427
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.
TOXICOLOGY: ASSESSING CHEMICAL HAZARDS • Typical variations in sensitivity to a toxic chemical within a population, mostly because of genetic variation. Figure 18-10
Number of individuals affected Majority of population Very sensitive Very insensitive Dose (hypothetical units) Fig. 18-10, p. 430
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
Water pollutant levels Air pollutant levels Soil/dust levels Food pesticide levels Nutritional health ? Mathematical measurements & modeling Overall health Lifestyle Predicted level of toxicant in people Personal habits Metabolism Genetic predisposition Accumulation Excretion Lung, intestine & skin absorption rates Fig. 18-11, p. 431
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.
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.
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.
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
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 Fig. 18-12, p. 433
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-A
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 55,000 Pollutants/toxins 30,600 Suicides 20,622 Homicides 17,000 Illegal drug use Fig. 18-A, p. 435
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
Cause of death Annual deaths 11 million (75) Poverty/malnutrition/ disease cycle 5 million (34) Tobacco 3.2 million (22) Pneumonia and flu 3 million (21) Air pollution 3 million (21) HIV/AIDS 2 million (14) Malaria 1.9 million (13) Diarrhea 1.7 million (12) Tuberculosis 1.2 million (8) Car accidents Work-related injury & disease 1.1 million (8) 1 million (7) Hepatitis B 800,000 (5) Measles Fig. 18-13, p. 435
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 18-14
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 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 10 hours Lifetime near nuclear plant Fig. 18-14, p. 436
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