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CHAPTER 9 Environmental Health The Rise and Fall—and Rise?—of DDT • DDT is the least expensive way of killing the mosquitoes that cause malaria. • DDT harms fish and birds, and can cause liver damage, cancer, and convulsions in humans. • In the 1970s many countries banned the use of DDT, but some African countries have resumed its use to control malaria. Talk About It Evidence shows that DDT damages ecosystems but helps eradicate malaria in areas where millions of people die of the disease each year. Should DDT be used in malaria-stricken areas? Why or why not? Lesson 9.1 An Overview of Environmental Health One third of death and disease in the least developed nations is a direct result of environmental causes. Lesson 9.1 An Overview of Environmental Health Types of Environmental Health Hazards • Biological: Viruses, bacteria, and other organisms that cause disease • Social: Lifestyle choices that endanger health • Chemical: Harmful artificial and natural chemicals in the environment • Physical: Natural disasters and ongoing natural phenomena, such as UV radiation, that can cause health problems Lesson 9.1 An Overview of Environmental Health Epidemiology • The study of disease in human populations—how and where they occur and how they can be controlled • Often involves studying large groups over long periods • Can determine statistical associations between health hazards and effects, but can’t prove the hazards actually caused the effects Lesson 9.1 An Overview of Environmental Health Toxicology • The study of how poisonous substances affect an organism’s health • Toxicity is a measure of how harmful a substance is. • Toxicologists look at toxicity by determining doseresponse relationships. Lesson 9.1 An Overview of Environmental Health Individual Responses • Sensitivity to hazards varies with age, sex, weight, and immune system health. • Many diseases have genetic as well as environmental factors. Did You Know? Thalidomide, a drug that currently shows promise for treatment of Alzheimer's, AIDS, and some cancers, caused thousands of severe birth defects when it was used as an anti-nauseal in the 1950s and 60s. Lesson 9.1 An Overview of Environmental Health Risk Assessment • Risk: The probability that a hazard will cause harm • Risk assessment: The process of measuring risk • Takes into account: • The type of hazard • How frequently humans will be exposed to it • How sensitive people are to it Lesson 9.2 Biological and Social Hazards Three quarters of infectious disease deaths are caused by five types of diseases: respiratory infections, AIDS, diarrheal diseases, tuberculosis, and malaria. Tuberculosis-causing bacteria Lesson 9.2 Biological and Social Hazards Infectious Diseases • Caused by pathogens • Spread by human and animal contact and through contaminated food and water • Cause of almost half of all deaths in developing nations • Covering your mouth when you cough, washing your hands often, and staying home from school if you’re sick help prevent the spread of infectious disease. Did You Know? In 2002, AIDS killed about 2 million people worldwide— almost equal to the entire population of Arkansas. Lesson 9.2 Biological and Social Hazards Emerging Diseases • Diseases appearing in the human population for the first time or suddenly beginning to spread rapidly • Humans have little or no resistance, and no vaccines have been developed. • Facilitated by increasing human mobility, growing antibiotic resistance, and environmental changes Lesson 9.2 Biological and Social Hazards Responding to Emerging Diseases • World Health Organization (WHO): Monitors health events worldwide and coordinates international responses to emerging diseases • Centers for Disease Control and Prevention (CDC): Responds to emerging diseases in the United States; the CDC developed pandemic plans to deal with the spread of the H1N1 flu virus. H1N1 Virus Lesson 9.2 Biological and Social Hazards Social Hazards • Some social hazards are easier to avoid than others. • Examples of social hazards include smoking, being exposed to secondhand smoke, living near an old toxic waste site, working with harmful chemicals, and eating fatty foods. Lesson 9.3 Toxic Substances in the Environment Chemicals are all around us, and all of them can be harmful to our health in large enough amounts. In other words, “The dose makes the poison.” Lesson 9.3 Toxic Substances in the Environment Chemical Hazards • Any chemical can be harmful in large enough amounts. • A pollutant is something released into the environment that has some harmful impact on people and other organisms. • Chemical hazards are not necessarily pollutants, and pollutants are not necessarily chemical hazards. Oil Pollution Lesson 9.3 Toxic Substances in the Environment Types of Chemical Hazards • Carcinogens: Cancer-causing chemicals • Chemical mutagens: Chemicals that cause genetic mutations • Teratogens: Chemicals that harm embryos and fetuses • Neurotoxins: Chemicals that affect the nervous system • Endocrine disruptors: Chemicals that interfere with the endocrine system Dust mite protein is a common allergen. • Allergens: Chemicals that overactivate the immune system Lesson 9.3 Toxic Substances in the Environment Indoor Chemical Hazards Lesson 9.3 Toxic Substances in the Environment Sources of Outdoor Chemical Hazards • In the air: Natural sources, such as volcanic eruptions, or human sources, such as pesticides • In the ground: Pesticide use, improper disposal of electronics, etc. • In the water: Chemical runoff from land or direct drainage of toxic substances into water A leaking oil line Lesson 9.3 Toxic Substances in the Environment Bioaccumulation and Biomagnification • Bioaccumulation: The buildup of toxic substances in the bodies of organisms • Biomagnification: The increased concentration of toxic substances with each step in a food chain • Persistent organic pollutants are biomagnified and stay in the environment for long periods of time and over long distances. Lesson 9.4 Natural Disasters Although we cannot prevent most natural disasters, there are steps that scientists, engineers, governments, and citizens can take to resist damage and deal with the aftermath. A landslide caused by the Great Sichuan Earthquake in Sichuan Province, China Lesson 9.4 Natural Disasters Earthquakes • Earth’s crust is broken into large pieces called tectonic plates, which float on a layer of molten rock. • Earthquakes tend to occur along active plate boundaries. • Earthquakes can damage structures and trigger landslides and tsunamis. Lesson 9.4 Natural Disasters Volcanoes • Openings in Earth’s crust that eject molten lava and other materials • Ash and gases from volcanic eruptions can block sunlight, causing temperatures to drop. • Eruptions can trigger landslides and mudflows. Did You Know? In 1991, Mount Pinatubo erupted in the Philippines, covering the area around the volcano with a layer of volcanic materials up to 180 m (600 ft) thick. • Molten lava can cover and destroy surrounding land. Lesson 9.4 Natural Disasters Storms • Tornadoes: Rotating funnels of air that can travel over 400 km (250 mi) per hr • Hurricanes: Storms that form over tropical oceans, with winds over 119 km (74 mi) per hour • Thunderstorms: Produce lightning and thunder, usually with heavy rain Did You Know? Hurricane Katrina, which struck New Orleans in 2005, caused more than $80 billion in damage and killed 1800 people. Lesson 9.4 Natural Disasters Avalanches • Masses of snow that slide down a slope • Conditions favoring avalanches: • • • • Slope greater than 30 degrees Unstable snowpack Heavy snowfall Warm temperatures Did You Know? A big North American avalanche can contain 230,000 m3 of snow—about the equivalent of 20 football fields filled with snow 3 m (10 ft) deep.