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CHAPTER 17. Environmental Hazards and Human Health. An introduction to hazards and human health. The highly virulent H5N1 avian flu first appeared in 1997 Infecting poultry, other birds, and humans Hundreds of millions of poultry have been slaughtered
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CHAPTER 17 Environmental Hazards and Human Health
An introduction to hazards and human health • The highly virulent H5N1 avian flu first appeared in 1997 • Infecting poultry, other birds, and humans • Hundreds of millions of poultry have been slaughtered • The 2009 H1N1 swine flu outbreak spread rapidly • The World Health Organization declared a global influenza pandemic • 39 new diseases have spread from animals to humans • SARS, the Ebola virus, West Nile virus, hantavirus • New diseases will appear as we change the environment
The old enemies • The new, emerging diseases are not our greatest threat • The common, familiar ones take the greatest toll • Malaria, diarrhea, respiratory viruses, worms • Especially in developing countries • In developed countries, cancer is the killer most closely linked to the environment • Due to our exposure to chemicals • Environmental health: connections between environmental hazards and human disease and death
Links between the environment and health • Pollution: the presence of a substance in the environment that because of its composition or quantity prevents functioning of natural processes and produces undesirable environmental or health effects • Pollutant: any material that causes pollution • Usually by-products of some desirable action • Agriculture, comfortable homes, transportation, etc. • Pollution has increased due to population and consumption • Along with accumulation of nonbiodegradable products (e.g., plastic, synthetic organic chemicals)
Pollution is everywhere • Any part of the environment can be polluted • Almost anything can be a pollutant • The only criterion? The addition of a pollutant results in undesirable changes • Impacts can be: • Aesthetic: hazy air, litter • On ecosystems: fish or forest die-offs • On human health: water contaminated with waste • Local (a contaminated well) or global (ozone depletion) • Too much of a natural compound (e.g., fertilizer)
Our existence necessitates waste production • We must meet our present needs by managing wastes • So they don’t jeopardize present or future generations • Identify the material(s) causing the pollution • Identify the source(s) of the pollutants • Clean up the environment • Prevent pollutants from entering the environment • Avoid the pollution altogether • Transitioning to a sustainable society will require a technology transition from pollution-intensive to environmentally friendly processes
Environmental health • Environment: the whole context of human life • The physical, chemical, and biological setting of where and how people live • Home, air, water, food, workplace, climate, etc. • Hazard: anything that can cause: • Injury, disease, death to humans • Damage to personal or public property • Deterioration or destruction of environmental parts
Hazards, risk, and vulnerability • Undesirable consequences do not necessarily follow a hazard • Risk: the probability of suffering injury, disease, death, or some loss as a result of exposure to a hazard • Vulnerability: some people (e.g., the poor) are more vulnerable to certain risks • Risk = Hazard x Vulnerability • The presence of avian flu in poultry: a hazard that presents the risk of humans getting the disease • People working with poultry are more vulnerable
The picture of health • Health: a state of complete physical, social, and mental well-being • Not just the absence of disease or infirmity • Environmental health focuses on disease • Health: the absence of disease • Two measures are used to study disease • Morbidity: the incidence of disease in a population • Mortality: the incidence of death in a population • Epidemiology: the study of the presence, distribution, and prevention of disease in populations
Public health • One of the most important activities of government: protecting the health of its people • Centers for Disease Control and Prevention (CDC) • Part of the Department of Health and Human Services • Provides tools and information to protect health • Involved in health risk management and prevention • Each state has its own public-health agency • Can require shots, quarantines, monitoring diseases, etc. • The U.S. has a huge health care industry • Medicare, Medicaid, hospitals, physicians, etc.
Other countries • Most countries have a ministry of health that acts on behalf of its people to manage and minimize health risks • Health policies are limited by information and funding • Limited funds should go to strategies that achieve the greatest risk prevention • Countries have access to the WHO • Established by the UN in 1948 • Everyone should get the highest possible level of health • Staffed by professionals and governed by the World Health Assembly
Life expectancy • A universal indicator of health • In 1955, it was 48 years • It is now 68 years and will rise to 73 by 2025 • Longer lives: due to social, medical, economic advances • Epidemiologic transition: decreasing death rates accompany development • Infectious diseases are replaced by diseases of aging • But 92 million children still die each year • Common diseases kill 47% of people in poor countries • Industry and intensive agriculture have their own hazards
Environmental hazards • Four classes of environmental hazards: • Cultural, biological, physical, chemical • There are two ways to consider hazards to health • Lack of access to resources (clean water, food) • Exposure to hazards in the environment that brings risk of injury, disease, or death • Cultural hazards: many factors that cause death or disability are a matter of choice • People engage in risky behavior (smoking, drinking, drugs, don’t exercise, risky sexual practices, etc.)
Cultural hazards can kill people • People derive pleasure or other benefits from cultural hazards • They are willing to take the risk they will not be hurt • Other cultural sources of mortality: living in inner cities, criminal activity • Cultural hazards cause 40% of U.S. deaths • Many causes of death are preventable • Acquired immune deficiency syndrome (AIDS) is a sexually transmitted disease • It is caused mainly by high-risk sexual behavior
Biological hazards • Through history, humans have battled bacteria and viruses • The black plague and typhus • The 19th century brought vaccinations and bacteriology • Bacteriologists discovered most bacterial diseases • The 20th century brought virology, antibiotics, immunizations • Global eradication of smallpox; victory over polio • The battle will never be won • Diseases are inevitable
Respiratory diseases • 25% of deaths are due to infectious or parasitic diseases • Respiratory infections (diphtheria, influenza, etc.) are the leading causes of death in this category • Pneumonia is the most deadly of these diseases • Respiratory diseases lead to death in developing nations • Mostly in children already weakened • Most children are infected by rotavirus • They die from untreated diarrhea in developing nations • Food or water contaminated with bacteria also cause diarrhea
Tuberculosis, malaria, and parasites • Mycobacterium tuberculosis infects one-third of all people • Tuberculosis has resurged due to complacency, HIV-weakened immune systems, and drug-resistant strains • Malaria kills 881,000 people each year • A mosquito infects a person with a protozoan parasite • Red blood cells are destroyed, leading to anemia, fever, chills, and malaise • 3.5 billion people suffer from parasitic worms • Hookworms and schistosomes
Physical hazards • Natural disasters include hurricanes, tornadoes, floods, fires, earthquakes, landslides, and volcanic eruptions • The result of hydrological, meteorological, or geological forces • Unimaginably dreadful events occurred in 2004-2005 • The Indian Ocean tsunami, Hurricane Katrina, Pakistan’s earthquake • Some hazards can’t be anticipated (tornadoes, earthquakes) • Others occur because of where people decide to live
Out of nowhere • The U.S. has 780 tornadoes/year, more than any other place • They are spawned from severe weather • Winds can reach 300 mph • They can kill hundreds • Some natural disasters are unavoidable • Earthquake-resistant buildings can be constructed • Tsunami early warnings are increasing • The poor are the least capable of anticipating and dealing with disasters
In harm’s way • Much loss from natural disasters is due to poor environmental stewardship • Deforested hillsides • Building on floodplains, below volcanoes, on geologic faults, marshes, and mangrove forests • People assume disasters happen to other people • They take risks to live in desirable places • Stupid zones could be created for areas that shouldn’t be built • Areas prone to hurricanes, earthquakes, volcanoes, etc.
Chemical hazards • Industrialization has resulted in technologies that use chemicals • Cleaning agents, pesticides, fuels, medicines, paints, etc. • Exposure is through ingestion, breathing, the skin, direct use, or by accident • Toxicity: condition of being harmful, deadly, or poisonous • Depends on exposure and dose (the amount absorbed) • Different people have different thresholds of toxicity • Children and embryos are most sensitive
Carcinogens • Many chemicals are hazardous even at very low levels • Heavy metals, organic solvents, pesticides • Acute poisoning episodes are understandable and preventable • But it is hard to determine effects of long-term exposure to low levels of substances • Carcinogens: cancer-causing agents • Cancer develops over decades, so it is hard to connect cause with the effect • There are 51 known and 188 suspected carcinogens • Developing nations have rising exposure to chemicals
Carcinogenesis • Carcinogenesis: the development of a cancer • It is a process with many steps spread over a long time • Five or more mutations must occur to initiate a cancer • Environmental carcinogens bind to, or disrupt, DNA • This prevents DNA from functioning • With a mutation, it may take 40 years to lead to a malignancy • Cells grow out of control and form tumors • Which may metastasize (spread) • The best strategy is prevention
Pathways of risk • What pathways lead from risks (of infection), exposure (to chemicals), and vulnerability (to hazards) to human deaths? • A very small number of risk factors cause the vast majority of premature deaths and disease • One major pathway for hazards: poverty • The world’s biggest killer in both developing and developed nations • People lack access to health care, clean water, nutritious food, healthy air, sanitation, and shelter
Poor vs. rich nations • Underweight children: the world’s number one risk factor • Strongly related to poverty • Malnutrition kills over 2.2 million children/year • Wealthy nations have healthier populations • People protect themselves from hazards • They die from diseases of old age (cancer, heart disease, etc.) • People in developing nations die from infectious diseases • Developed nations have better-educated people • They improve their hygiene, immunize children, recognize dangerous symptoms (e.g., dehydration)
Priorities • Education, nutrition, and wealth do not explain everything • A nation may make deliberate policy choices to improve the health of its population • Instead of militarization or power sources • Costa Rica, China, and Sri Lanka have longer life expectancies and lower infant mortality than expected • They focused public resources on immunization, upgrading sewer and water systems, and land reform
The cultural risk of tobacco use • Lifestyle choices pose a high risk of accidents and death • Not exercising, overeating, fast driving, alcohol, etc. • Tobacco is the leading cause of death in the U.S. • Fourth cause of death globally • Tobacco use is declining in developed countries • But not in developing countries • It remains high in former socialist countries of eastern Europe • 19.8% (43.4 million) of U.S. adults smoke • Half will die or become disabled
Marlboro country? • Tobacco is the only product sold that kills half its users • It is clearly correlated with cancer and other lung diseases • It is responsible for 29% of U.S. cancer deaths • 5.4 million die worldwide each year • Synergistic effects: smokers living in polluted air or working with asbestos have higher rates of lung cancer • Black lung disease occurs mainly in smokers • Smoking costs the U.S. $193 billion/yr in health care costs and lost job productivity
Decreasing tobacco use • Raising taxes: the most effective measure to reduce tobacco use • Providing billions of dollars to state and federal governments • Other measures to reduce smoking include warnings, smoke-free workplaces, non-smoking areas, and banning smoking on domestic flights • The U.S. smoking population dropped from 42% to 19.8% since warnings began
Secondhand smoke • In 1999 the EPA classified environmental tobacco smoke (ETS), secondhand smoke, as a Class A (known) carcinogen • A serious and substantial public health risk • Specific steps now protect children in public places • The Occupational Safety and Health Administration is working to protect workers from ETS • In 1999, Congress gave the Food and Drug Administration sweeping power to regulate tobacco • Overcoming efforts of the powerful tobacco lobby
Legally speaking • The attorneys general of several states sued tobacco companies • In 1998, 46 states reached a $246 billion settlement • Tobacco companies would reimburse states for smoking-related illnesses • Help finance programs to discourage smoking • Other lawsuits have not been successful • Judges ruled that earlier court rulings forbade them from imposing fines
FCTC and EMPOWER • The WHO’s 2003 Framework Convention on Tobacco Control aims to reduce the spread of smoking • Bill Gates and New York City’s Mayor Bloomberg gave the WHO $500 million to combat global smoking • Monitor tobacco use and prevention policies • Protect people from tobacco use • Offer help to those who want to quit • Warn about dangers of tobacco • Enforce bans on advertising, promotion, sponsorship • Raise taxes on tobacco
Risk and infectious diseases • Epidemiology is “medical ecology” • Epidemiologists trace a disease’s location, transmission, and consequences • Infectious diseases and parasites are more common in developing countries • Inadequate hygiene, inferior sewage treatment • A lack of resources for public-health infrastructure • Developed nations also have outbreaks of diseases • In 1993 Milwaukee’s (Wisconsin) water supply was contaminated by animal wastes, hospitalizing over 4,000
Tropical diseases • The tropics have ideal climates for insect-borne diseases • Mosquitoes are vectors for yellow fever, dengue fever, elephantiasis, Japanese encephalitis, West Nile, malaria • Malaria is the most serious • Control of malaria focuses on vector control: using pesticides on the Anopheles mosquito • Or treatment strategies: curing infected people • Malaria has been eradicated in the U.S. • DDT is a successful, yet controversial, control for mosquitoes in developing countries
Net results • Giving children insecticide-treated nets over their beds reduces mortality from all causes • Bed nets, indoor DDT spraying, and effective drugs reduce malaria deaths • A cost-effective, large-scale intervention in Africa • The Plasmodium protozoan is becoming resistant to drugs • Chloroquine is now ineffective against malaria • ACT (artemisinin combination therapy) is effective • But resistance is appearing
Good news • Molecular biologists have sequenced the genomes of the Anopheles mosquito and P. falciparum parasite • Targeting weak points in both organisms • Development of new drugs and vaccines will further reduce malaria • The Global Malaria Action Plan (GMAP): intends to eventually eradicate malaria • Will require billions of dollars • Will meet the Millennium Development Goal target
