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Explore the links between environmental hazards and human health, including pollution, diseases from animals, and the importance of public health agencies in managing risks effectively.
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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
