14 Environmental Health and Toxicology Chapter Objectives This chapter will help you: Identify major environmental health hazards and explain the goals of environmental health Describe the types, abundance, distribution, and movement of toxic substances in the environment Discuss the study of hazards and their effects, including case histories, epidemiology, animal testing, and dose-response analysis Evaluate risk assessment and risk management Compare philosophical approaches to risk Describe regulatory policy in the United States and internationally Lecture Outline I. Central Case: Poison in the Bottle: Is Bisphenol A Safe? A. The chemical bisphenol A (BPA for short) has been associated with everything from neurological effects to miscarriages, yet it’s in hundreds of products we use every day, and there’s a better than 9 in 10 chance that it is coursing through your body right now. B. With so many uses, bisphenol A, an organic compound with the chemical formula C15H16O2, has become one of the world’s most-produced chemicals; each year we make 1 pound of BPA for each person on the planet, and over 6 pounds per person in the United States! C. Bisphenol A leaches out of its many products and into our food, water, air, and bodies. Fully 93% of Americans carry detectable concentrations in their urine, according to the latest National Health and Nutrition Examination Survey conducted by the Centers for Disease Control and Prevention (CDC). D. Over 200 studies with rats, mice, and other animals have shown many apparent effects of BPA, including a wide range of reproductive abnormalities. E. Scientists say this is because BPA mimics the female sex hormone estrogen; that is, it is structurally similar to estrogen and can induce some of its effects in animals. F. In reaction to the burgeoning research, a growing number of researchers, doctors, and consumer advocates are calling on governments to regulate bisphenol A and for manufacturers to stop using it. G. In 2008, Canada became the first nation to declare bisphenol A toxic. It banned the sale, import, and advertising of baby products using BPA. H. In the face of mounting press coverage and public concern, many companies are choosing to voluntarily remove BPA from their products. II. Environmental Health 1. The study and practice of environmental health assesses environmental factors that influence human health and quality of life. A. We face four types of environmental hazards. 1. Physical hazards arise from processes that occur naturally in our environment and pose risks to human life or health. Examples include ultraviolet (UV) radiation from sunlight, or discrete events such as earthquakes, volcanic eruptions, fires, floods, blizzards, landslides, hurricanes, and droughts. 2. Chemical hazards include many of the synthetic chemicals that our society produces, such as disinfectants and pesticides, and also include chemicals produced naturally by organisms. 3. Biological hazards result from ecological interactions among organisms. When we become sick from a virus, bacterial infection, or other pathogen, we are suffering parasitism by other species that are simply fulfilling their ecological roles, and this is what we call infectious disease. 4. Hazards that result from our place of residence, our socioeconomic status, our occupation, or our behavioral choices can be thought of as cultural hazards or lifestyle hazards. Choosing to smoke, poor diet, and living in proximity to toxic waste are all cultural hazards. B. Many environmental health hazards exist indoors. 1. Cigarette smoke and radon are leading indoor hazards and are the top two causes of lung cancer in developed nations. 2. Another indoor hazard is asbestos causing a condition called asbestosis. 3. Lead poisoning is another indoor health hazard. When ingested, lead, a heavy metal, can cause damage to the brain, liver, kidney, and stomach; learning problems and behavioral abnormalities; anemia; hearing loss; and even death. 4. A recently recognized hazard is a group of chemicals known as polybrominated diphenyl ethers (PBDEs). These chemicals appear to be endocrine disruptors, affecting thyroid hormones in animals, and have been banned in Europe. C. Disease is a major focus of environmental health. 1. Many major killers, such as cancer, heart disease, and respiratory disorders, have genetic bases but are also influenced by environmental factors. 2. Malnutrition can foster a wide variety of illnesses, as can poverty, poor hygiene, lifestyle choices, and lack of exercise. 3. Over half the world’s deaths result from non-infectious diseases, such as cancer and heart disease, while 1 death in 11 is due to injuries. 4. In developed nations like the United States, lifestyle trends are altering the prevalence of non-infectious disease in ways both good and bad. 5. Although infectious disease accounts for fewer deaths than non-infectious disease, it robs society of more years of human life because it tends to strike people at all ages, including the very young. D. Infectious disease interacts with social and environmental influences. 1. Many diseases are spreading because we are so mobile in our modern era of globalization. 2. The changes we cause to our environment can also cause diseases to spread. 3. To predict and prevent infectious disease, environmental health experts assess the complicated relationships among technology, land use, and ecology. E. Health workers are fighting disease in many ways. 1. Perhaps the best way to reduce disease is to improve the basic living conditions of the world’s poor. Other than providing them food security, this means ensuring their access to safe drinking water and improving sanitation by minimizing exposure to human waste, garbage, and wastewater. 2. Another important pursuit is to expand access to health care. In developing nations, this includes opening clinics, immunizing children against diseases, providing prenatal and postnatal care for mothers and babies, and making generic and inexpensive pharmaceuticals available. 3. Education campaigns play a vital role in rich and poor nations alike. 4. Such efforts are being spearheaded internationally by the United Nations, the World Health Organization, the U.S. Agency for International Development, and by non-governmental organizations and funding agencies. F. Toxicology is the study of poisonous substances. 1. Toxicology is the science that examines the effects of poisonous substances on humans and other organisms. 2. Toxicologists assess and compare substances to determine their toxicity, the degree of harm a chemical substance can inflict. 3. A toxic substance, or poison, is called a toxicant, but any chemical substance may exert negative impacts if we ingest or expose ourselves to enough of it. 4. These trends have driven the rise of environmental toxicology, which deals specifically with toxic substances that come from or are discharged into the environment. G. Risks must be balanced against rewards. III. Toxic Substances in the Environment 1. Our environment contains countless natural substances that may pose health risks. These include toxins, toxic chemicals manufactured in the tissues of living organisms, and many synthetic (artificial, or human-made) chemicals. A. Synthetic chemicals are all around us. 1. Thousands of synthetic chemicals have been manufactured and many have found their way into soil, air, and water. B. Synthetic chemicals are in all of our bodies. 1. As a result of exposure, every one of us carries traces of numerous industrial chemicals in our bodies. 2. Not all synthetic chemicals pose health risks, and relatively few are known with certainty to be toxic. However, very few have been thoroughly tested. C. Silent Spring began the public debate over synthetic chemicals. 1. Rachel Carson was a naturalist, author, and government scientist. 2. Using scientific studies, medical case histories, and other data, she showed that DDT and artificial pesticides in general were hazardous to people, wildlife, and the environment. 3. Carson’s book was a bestseller and generated significant social changes in views and actions toward the environment. 4. The United States does not use DDT, but manufactures and exports it to countries that still use it, especially for mosquito control. Certain species of mosquitoes are vectors for malaria, which is considered to be a greater risk than the toxic effects of the pesticide. D. Toxicants come in different types. 1. Carcinogens are substances or types of radiation that cause cancer. 2. Mutagens are chemicals that cause mutations in the DNA of organisms. 3. Chemicals that cause harm to the unborn are called teratogens. 4. Neurotoxins assault the nervous system. 5. Allergens overactivate the immune system, causing an immune response when one is not necessary. 6. Endocrine disruptors are toxicants that interfere with the endocrine system. E. Toxicants may concentrate in water. 1. Water runoff often carries low amounts of toxicants from large areas of land and concentrates them in small volumes of surface water. 2. Many chemicals are soluble in water, and thus are very accessible to organisms. This is why aquatic animals such as fish, frogs, and stream invertebrates are especially good indicators of pollution. F. Airborne substances can travel widely. 1. Because many chemical substances can be transported by air, chemicals can exert impacts far from the site of their origin and use. Airborne transport of pesticides is sometimes termed pesticide drift. 2. Earth’s polar regions are particularly