Lecture Outlines Chapter 14 Environment: The Science behind the Stories 4th Edition Withgott/Brennan This lecture will help you understand: Environmental health and hazards Toxic substances in the environment Hazards and their effects Risk assessment and risk management Philosophical approaches to risk Regulatory policy in the U.S. and internationally The four types of environmental hazards Environmental health = assesses environmental factors that influence human health and quality of life Including natural and human-caused factors Physical hazards = occur naturally in our environment Earthquakes, volcanoes, fires, floods, droughts We can?t prevent them, but we can prepare for them We increase our vulnerability by deforesting slopes (landslides), channelizing rivers (flooding), etc. We can reduce risk with better environmental choices Cultural (lifestyle) hazards Cultural = result from where we live, our socioeconomic status, our occupation, our behavioral choices We can minimize some, but not all, of these hazards Smoking, drug use, diet and nutrition, crime, mode of transportation Health factors (e.g., living near toxic waste) are often correlated with poverty Chemical and biological hazards Chemical hazards = synthetic chemicals such as pharmaceuticals, disinfectants, pesticides Harmful natural chemicals (e.g., venom) also exist Biological hazards = result from ecological interactions Viruses, bacteria, and other pathogens Infectious disease = species parasitize humans, fulfilling their ecological roles Vector = an organism that transfers a pathogen to a host We can?t avoid risk, but we can reduce infection Four types of environmental hazards Disease is a major focus of environmental health Despite our technology, disease kills most of us Disease has a genetic and environmental basis Cancer, heart disease, respiratory disorders Poverty and poor hygiene foster illnesses Infectious diseases kill millions Infectious diseases kill 15 million people/year Half of all deaths in developing countries Money lets developed countries have access to hygiene and medicine Infectious and noninfectious diseases Lifestyles in developed nations affect diseases U.S. smoking dropped 38% But obesity has doubled Public health decreases some infectious diseases Some (AIDS) are spreading Some develop resistance to antibiotics Diseases, the environment, and society Our mobility spreads diseases West Nile Virus spread from Africa to all lower 48 U.S. states in 5 years New diseases are emerging H5N1 avian flu, H1N1 swine flu Climate change will expand the range of diseases To predict and prevent diseases, experts deal with complicated interrelationships In technology, land use, and ecology Health workers fight disease The best way to reduce disease? Improve the basic living conditions of the poor Food security, sanitation, clean drinking water Expanded access to health care Health clinics, immunizations, pre- and postnatal care Education campaigns work in rich and poor nations Public service and governments give advice Packaging and ads advise us on smoking, etc. Sex and reproductive health education slows population growth and spread of HIV/AIDS Working together to fight disease Agencies, organizations, and governments work together The United Nations, the World Health Organization, U.S. Agency for International Development, etc. Private organizations donate millions of dollars Pharmaceutical companies research new medicines Sanitation and drinking water are improving Toxicology studies poisonous substances Toxicology = the study of the effects of poisonous substances on humans and other organisms Toxicity = the degree of harm a toxicant can inflict Toxicant = any toxic substance (poison) ?The dose makes the poison? = toxicity depends on the combined effect of the chemical and its quantity Environmental toxicology = deals with toxic substances that come from or are discharged into the environment Studies health effects on humans, other animals, and ecosystems Toxicants come in different types Carcinogens = cause cancer Hard to identify because of the long time between exposure and onset of cancer Mutagens = cause DNA mutations Can cause cancer Teratogens = cause birth defects in embryos Neurotoxins = assault the nervous system Allergens = overactivate the immune system Endocrine disruptors = affect the endocrine (hormone) system Poison in the bottle: is bisphenol A (BPA) safe? BPA causes cancer, nerve damage, and miscarriages In extremely low doses It is in hundreds of products Cans, utensils, baby bottles, laptops, toys BPA leaches into food, water, air, and bodies 93% of Americans have it in their bodies Bisphenol A mimics estrogen BPA mimics estrogen, a female hormone In lower levels than set by regulatory agencies Researchers, doctors, and consumer advocates want regulation The chemical industry insists it is safe Some countries and states have banned it Many companies are removing it voluntarily Indoor environmental health hazards Radon = a highly toxic, radioactive gas that is colorless and undetectable It can build up in basements Asbestos = a mineral that insulates, muffles sounds, and resists fire Asbestosis = scarred lungs that cease to function Lead poisoning Lead poisoning = caused by lead, a heavy metal Damages the brain, liver, kidney, and stomach Causes learning problems, behavior abnormalities, and death Exposure is from drinking water that flows through lead pipes or from lead paint Education led to declines in poisoning, but China still used it in toy paint until recently A recently recognized hazard Polybrominated diphenyl ethers (PBDEs) = has fire-retardant properties Used in computers, televisions, plastics, and furniture Persist and accumulate in living tissue Mimic hormones and affect thyroid hormones Also affect brain and nervous system development and may cause cancer Concentrations are rising in breast milk Now banned in Europe, concentrations have decreased The U.S. has not addressed the issue Toxic substances in the environment The environment contains natural chemicals that may pose health risks Toxins = toxic chemicals made in tissues of living organisms But synthetic chemicals are also in our environment Every human carries traces of industrial chemicals The U.S. makes or imports 250 lb of chemicals for every person in the country Chemicals are in the air, water, and soil 80% of U.S. streams contain 82 contaminants Antibiotics, detergents, drugs, steroids, solvents, etc. 92% of all aquifers contain 42 volatile organic compounds (from gasoline, paints, plastics, etc.) Less than 2% violate federal health standards for drinking water Pesticides are present in streams and groundwater in levels high enough to affect aquatic life Synthetic chemicals are in all of us Every one of us carries traces of hundreds of industrial chemicals in our bodies Including toxic persistent organic pollutants restricted by international treaties Babies are born ?pre-polluted? ? 232 chemicals were in umbilical cords of babies tested Not all synthetic chemicals pose health risks But very few of the 100,000 chemicals on the market have been tested Silent Spring began the debate over chemicals Rachel Carson?s Silent Spring (1962) showed DDT?s risks to people, wildlife, and ecosystems Chemical companies challenged the book Discrediting Carson?s personal reputation DDT was banned in the U.S. in 1973 But is still made in the U.S. and exported In the 1960s, untested pesticides were sprayed over public areas, with assumption they would do no harm Many products mimic female hormones Bisphenol A binds to estrogen receptors Phthalates in plastics disrupt hormones Toys, perfumes, makeup Birth defects, cancer, reproductive effects In the bodies of everyone in the U.S. Endocrine disruptors mimic hormones Hormones stimulate growth, development, sexual maturity Synthetic chemicals Block hormones Mimic hormones Toxins may concentrate in water Runoff carries toxins from land to surface water Chemicals in the soil can leach into groundwater Contaminating drinking water Chemicals enter organisms through drinking or absorption Aquatic organisms (fish, frogs, etc.) are good pollution indicators Contaminants in streams and rivers enter drinking water and the air Routes of chemical transport Toxicants can accumulate and biomagnify Toxicants in the body can be excreted, degraded, or stored Fat-soluble toxicants are stored in fatty tissues Bioaccumulation = toxicants build up in animal tissues Biomagnification = concentrations of toxicants become magnified Near extinction of peregrine falcons and bald eagles Airborne substances can travel widely Chemicals can travel by air Their effects can occur far from the site of use Pesticide drift = airborne transport of pesticides Synthetic chemicals are found globally In arctic polar bears, Antarctic penguins, and people in Greenland Some toxicants persist Toxins can degrade quickly and become harmless Or they may remain unaltered and persist for decades Rates of degradation depend on the substance, temperature, moisture, and sun exposure Breakdown products = simpler products that toxicants degrade into May be more or less harmful than the original substance DDT degrades into DDE, which is also highly persistent and toxic Not all toxicants are synthetic Toxic chemicals also exist naturally and in our food Don?t assume natural chemicals are all healthy and synthetic ones are all harmful Some scientists feel that natural toxicants dwarf our intake of synthetic chemicals Natural defenses are effective against synthetics Environmentalists say synthetic toxins: Are harder to metabolize and excrete Persist and accumulate Enter people in ways other than in food Wildlife studies integrate field and lab work Museum collections provide data from times before synthetic chemicals were used Measurements from animals in the wild can be compared to controlled experiments in the lab Alligators and frogs show reproductive abnormalities due to endocrine disruption from pesticides Human studies Case history approach = studies individual patients Autopsies tell us about lethal doses Don?t tell about rare, new, or low-concentration toxins Don?t tell about probability and risk Epidemiological studies = large-scale comparisons between exposed and unexposed groups Studies can last for years Yield accurate predictions about risk Measure an association between a health hazard and an effect ? but not necessarily the cause of the effect Manipulative experiments show causation Animals are used as test subjects Mammals share evolutionary history Substances that harm rats and mice probably harm us Some people object to animal tests Medical advances would be far more difficult without them New techniques may replace some live-animal testing Human cell cultures, bacteria, etc. Dose-response analysis Dose = amount of substance the test animal receives Response = the type or magnitude of negative effects Dose-response curve = the dose plotted against the response Dose-response analysis = measures the effect a toxicant produces or the number of animals affected At different doses Dose response curves LD50/ED50= the amount of toxicant required to kill (affect) 50% of the subjects A high number indicates low toxicity Threshold dose = the level where certain responses occur Organs can metabolize or excrete low doses of a toxicant Scientists extrapolate downward from animal studies to estimate the effect on humans Strange dose-response curves Sometimes a response decreases as a dose increases U- or J-shaped or an inverted-U dose-response curve Counterintuitive curves occur with endocrine disruptors The hormone system is geared to respond to minute concentrations (e.g., hormones) The endocrine system is vulnerable to extremely low concentrations of chemicals Endocrine disruptions pose challenges Unconventional dose-response curves are hard to study Or use to set safety standards for toxic substances Theo Colburn?s Our Stolen Future (1996) describes how synthetic chemicals may be changing hormones Thousands of studies show that endocrine disruptors affect reproduction, development, immune functions, nervous systems, etc. Industry-funded research shows no problems, while government research shows harmful effects Individuals vary in their responses to hazards Different people respond differently to hazards Affected by genetics, surroundings, etc. People in poor health are more sensitive Sensitivity also varies with sex, age, and weight Fetuses, infants, and young children are more sensitive The Environmental Protection Agency (EPA) sets standards for responses based on adult responses Often, standards are not low enough to protect babies The type of exposure affects the response Acute exposure = high exposure to a hazard for short periods of time Easy to recognize Stem from discrete events: ingestion, oil spills, nuclear accident, etc. Chronic exposure = low exposure for long periods of time More common but harder to detect and diagnose Affects organs gradually: lung cancer, liver damage Cause and effect may not be easily apparent Mixes may be more than the sum of their parts We can?t determine the impact of mixed hazards They may act in ways that cannot be predicted from the effects of each in isolation Mixed toxicants can sum, cancel out, or multiply each other?s effects Synergistic effects = interactive impacts that are greater than the sum of their constituent effects New impacts may arise from mixing toxicants DDE may cause or inhibit sex reversal, depending on the presence of other chemicals We express risk in terms of probability Exposure to health threats doesn?t automatically produce an effect Rather, it causes some probability (likelihood) of harm A substance?s threat depends on its identity and strength Chance and frequency of an encounter An organism?s exposure and sensitivity to the threat Risk = the probability that some harmful outcome will result from a given action, event, or substance Probability = describes the likelihood of a certain outcome Perceptions of risk may not match reality We try to minimize risk But perception may not match reality Flying versus driving We feel more at risk when we do not control a situation We fear nuclear power and toxic waste But not smoking or overeating Everything we do involves some risk Analyzing risk quantitatively Risk assessment = the quantitative measurement of risk Compares risks involved in different activities or substances It identifies and outlines problems Risk assessment has several steps: The scientific study of toxicity Assessing an individual or population?s exposure to the substance (frequency, concentrations, length) Teams of scientific experts review hundreds of studies Regulators and the public benefit from informed summaries Risk management Risk management = decisions and strategies to minimize risk Federal agencies manage risk The U.S. has the Centers for Disease Control (CDC), the EPA, the Food and Drug Administration (FDA) Scientific assessments are considered with economic, social, and political needs and values Comparing costs and benefits is hard Benefits are economic and easy to calculate Health risks (costs) are hard-to-measure probabilities of a few people suffering and lots of people not The process of risk management Because of the lack of equivalency in measuring costs and benefits, risk management stirs up debate Two approaches to determining safety Innocent-until-proven-guilty approach: assumes a substance is harmless Helps technological innovation and economic advancement But it allows dangerous substances to be used Precautionary principle: assumes a substance is harmful until it is shown to be harmless Identifies troublesome toxicants before being released May impede the pace of technology and economic advance Two approaches for determining safety Who should have to prove a product is safe: the manufacturers or government/citizens? Philosophy affects policy Different nations use different policies for regulating synthetic substances Europe incorporates the precautionary principle The U.S. uses the innocent-until-proven-guilty approach Federal agencies involved in tracking and regulating synthetic chemicals include: The FDA: monitors food, food additives, cosmetics, drugs, medical devices The EPA: regulates pesticides and chemicals not covered by other laws Balancing risks and rewards There is a tradeoff between the risk and reward of most hazards We must judge how these compare We use bisphenol A despite its health risks Are safer and affordable alternatives available? Don?t forget, chemicals have given us our high standard of living Food, medicine, conveniences EPA regulation is only partly effective The Toxic Substances Control Act (1976) = the EPA monitors chemicals made in or imported into the U.S. The EPA can ban substances that pose excessive risk Many health advocates think the TSCA is too weak Of 83,000 chemicals, only five have been restricted To push for more testing, toxicity must already be proven, but testing is minimal Only 10% of chemicals have been tested for toxicity Fewer than 1% are regulated Almost none have been tested for endocrine, nervous, or immune system damage FIFRA (1974) The Federal Insecticide, Fungicide, and Rodenticide Act Charges the EPA with ?registering? new pesticides manufacturers want to market The EPA asks the manufacturer to provide information on safety assessments The EPA examines ingredients, use, etc. to determine risks to people, other organisms, water, or air It approves, denies, or sets limits on the chemical?s sale and use and approves language used on the label Hazardous chemicals are approved if economic benefits outweigh hazards Europe?s REACH program The EU?s REACH program (Registration, Evaluation, Authorization, and Restriction of Chemicals) shifts the burden of proof for safety to industry Helps industries research and develop safer products Chemicals will be approved, deemed unsafe, or tested further 1,500 chemicals will be replaced with safer ones REACH will cost industry $3.8?7 billion over 11 years Health benefits will be $67 billion over 30 years The Stockholm Convention on Persistent Organic Pollutants (POPs) Enacted in 2004 and ratified by over 150 nations POPs = toxic, persistent chemicals Bioaccumulate and biomagnify Can travel long distances The ?dirty dozen? = the 12 most dangerous POPs The Stockholm Convention sets guidelines for phasing out these chemicals Encouraging transition to safer alternatives Conclusion International agreements show that governments are working to protect society, wildlife, and ecosystems from toxic chemicals and environmental hazards But solutions need more than government regulations Consumer choice affects industries Once scientific results are in, society?s approach to risk management determine what policies are enacted A safe and happy future depends on knowing the risks some hazards pose Then replacing those substances with safer ones QUESTION: Review Which of the following is a cultural hazard? Earthquake Smoking Virus A pesticide All are biological hazards QUESTION: Review Which of the following damages the brain and liver, causes learning problems, and comes from water flowing through certain pipes? Radon Asbestos Lead Polybrominated diphenyl ethers QUESTION: Review Toxicology is: The study of the effects of poisonous substances Any toxic substance Any substance that causes environmental degradation The degree of harm a substance can cause QUESTION: Review A ?carcinogen? causes: Cancer Mutations Birth defects Problems in the hormonal system QUESTION: Review A study that studies individual patients (i.e., autopsies) uses: An epidemiological study A case history approach Mainly private funding sources Probability and risk as major components of the study QUESTION: Review Which statement about endocrine disruptors is NOT true? They may show unconventional dose-response curves. They affect reproduction, development, and immunity. Industry studies show how really harmful they are. The endocrine system is vulnerable to very low levels of these disruptors. QUESTION: Interpreting Graphs and Data Our perception, and the reality, of risk often do not match. Given this graph (reality), and your knowledge of sources of anxiety (perception), which statement is correct? Smoking is dangerous and we are anxious about it. Smoking is not dangerous, but we are anxious about it. Fire is dangerous, and we are anxious about it. Fire is not dangerous, but we are anxious about it. QUESTION: Interpreting Graphs and Data If the ?low? dose = 5 units of a chemical, the ?medium? dose = 10 units, and the ?high? dose = 15 units, how much of the chemical is required to kill 50% of the study population? About 5 units About 10 units About 15 units You can?t tell from the graph. QUESTION: Viewpoints Should the United States be able to manufacture and export chemicals that have been banned in the United States? No; if we won?t have it in the United States, we shouldn?t be able to make and export it to others. Yes, because the money we get from selling it will help our economy. Yes; let people decide what they want to do. Yes; in fact, chemicals should not be banned in the United States either. QUESTION: Viewpoints How should the U.S. government regulate chemicals? The government should force industries to prove their products are safe. The government should prove a chemical is dangerous before it is taken off the market. Industry knows chemicals best, so decisions such as this should be left up to the industry. As long as the product makes money and jobs for the industry, it should be allowed, even if some people get sick or die from it.
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