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2 This lecture will help you understand:Environmental health and hazards Toxic substances in the environment and factors that affect their toxicity Defenses organisms posses against toxic substances Movement of toxic substances and their affect on ecosystems Hazards and their effects Risk assessment and risk management Philosophical approaches to risk Regulatory policy in the United States and internationally

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4 Central Case Study: Poison in the Bottle: Is Bisphenol A (BPA) Safe?BPA is linked to cancer, nerve damage, and miscarriages In extremely low doses Used to make hard plastic found 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 Negative effects occur at extremely low doses BPA mimics estrogen, a female hormone In lower levels than set by regulatory agencies

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6 Central Case Study: Poison in the Bottle: Is Bisphenol A (BPA) Safe?Numerous scientific panels have examined the health risk of BPA Some have found no concern (U.S. FDA in 2008) Other have found reason for concern (U.S. FDA’s science advisory panel in 2009) Numerous countries had banned the use of BPA in baby bottles by 2011 Public and scientific opinion wanted BPA regulated in the United States In 2012, the FDA rejected a proposed ban on its use Other countries have banned BPA for some uses Some industries are removing BPA on their own

7 Environmental Health Environmental health = field that assesses environmental factors that influence human health and quality of life Including natural and human-caused factors Practitioners seek to prevent adverse effects on human health and ecological systems Many environmental health hazards exist in the world around us

8 We face four types of environmental hazardsPhysical hazards = hazards that occur naturally in our environment Exposure to ultraviolet (UV) radiation from sunlight Earthquakes, volcanoes, fires, floods, droughts We can’t prevent them, but we can prepare for them We increase our vulnerability by deforesting slopes (e.g., landslides), channelizing rivers (e.g., flooding), etc. We can reduce risk with better environmental choices

9 We face four types of environmental hazardsChemical hazards = synthetic chemicals such as pharmaceuticals, disinfectants, pesticides Harmful natural chemicals (e.g., venom) also exist and chemicals that we take from nature and process

11 We face four types of environmental hazardsBiological hazards = result from ecological interactions Viruses, bacteria, and other pathogens Infectious disease = disease occurring when species parasitize humans, fulfilling their ecological roles Vector = an organism that transfers a pathogen We can’t avoid risk, but we can reduce infection

12 We face four types of environmental hazardsCultural hazards = result from where we live, our socioeconomic status, our occupation, our behavioral choices Smoking, drug use, diet and nutrition, crime, mode of transportation—some we control, others we can not Health factors (e.g., living near toxic waste) are often correlated with poverty

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14 Disease is a major focus of environmental healthDespite our technology, disease kills most of us Disease has a genetic and environmental basis Cancer, heart disease, respiratory disorders have some genetic basis Air pollution, poverty, and poor hygiene foster illnesses Noninfectious diseases cause over half of the world’s deaths Infectious diseases account for 1 in 4 deaths 15 million people/year

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16 Disease is a major focus of environmental healthWhere you live helps determine your disease Infectious disease causes half of all deaths in developing countries Money lets developed countries have access to hygiene and medicine to combat these diseases

17 Disease is a major focus of environmental healthLifestyles in developed nations affect diseases U.S. smoking dropped 42% But obesity has more than doubled Public health efforts decrease some infectious diseases But some (AIDS) are spreading Some develop resistance to antibiotics

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19 Social and environmental factors can influence the spread of infectious diseaseOur mobility spreads diseases worldwide Severe acute respiratory syndrome (SARS) in 2003 H1N1 swine flu in 2009–2010 Climate change will expand the range of diseases New disease threats may arise Some pathogens evolve rapidly Humans can alter existing diseases to make them more deadly—bioterrorism is a growing concern To predict and prevent diseases, experts deal with complicated interrelationships between technology, land use, and ecology

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21 We are fighting disease with diverse approachesOne of the best way to reduce disease is to improve the basic living conditions of the poor Food security, sanitation, clean drinking water Also, provide expanded access to health care Health clinics, immunizations, pre- and postnatal care

22 We are fighting disease with diverse approachesEducation campaigns work in rich and poor nations 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 The Bill and Melinda Gates Foundation has donated over $15 billion to global health programs since 1994

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24 Toxicology is the study of chemical hazardsToxicology = 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

25 Toxicology is the study of chemical hazardsWe have been adding increased amounts and numbers of chemicals into the environment around us Environmental toxicology = deals with toxic substances that come from or are discharged into the environment Studies health effects on humans, other animals, and ecosystems

26 Many environmental health hazards exist indoorsAmericans spend roughly 90% of their lives indoors Indoor spaces can be rife with hazards Radon = a highly toxic, radioactive gas that is colorless and undetectable Can build up in basements Found in areas with certain types of bedrock Asbestos = a mineral that insulates, muffles sounds, and resists fire Asbestosis = disorder that occurs when inhaled crystals of asbestos cause scarred lungs that cease to function Can lead to lung cancer

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28 Many environmental health hazards exist indoorsLead 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 Efforts in the United States have led to declines in poisoning, but China still used lead paint in toys until recently In 2012, the Centers for Disease Control (CDC) cut the danger threshold for lead in children’s blood from 10 to 5 micrograms/deciliter

29 Many environmental health hazards exist indoorsPolybrominated diphenyl ethers (PBDEs) = a group of chemicals with 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 that they’re banned in Europe, concentrations have decreased The United States has not addressed the issue

30 Risks must be balanced against rewardsAs with most hazards, there is a tradeoff between the risk of harm and reward We must judge how these compare We use bisphenol A despite its health risks Are safer and affordable alternatives available? Chemicals have given us our high standard of living Food, medicine, conveniences

31 Toxic Substances and Their Effects on OrganismsThe environment contains natural chemicals that may pose health risks Toxins = toxic chemicals made in tissues of living organisms Chemicals plants use to defend themselves But synthetic chemicals are also in our environment Many thousands of different chemicals have been manufactured The United States makes or imports 113 kg (250 lb) of chemicals for every person in the country each year

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33 Synthetic chemicals are all around us—and in usA 2002 study found that 80% of U.S. streams contain 82 contaminants Antibiotics, detergents, drugs, steroids, solvents, etc. A 2006 study of groundwater found 18% of wells and 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 not high enough to affect human health But high enough to affect aquatic life

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35 Synthetic chemicals are in all of our bodiesEvery 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 Nine out of 10 umbilical cords contained BPA Not all synthetic chemicals pose health risks But very few of the 100,000 chemicals on the market have been thoroughly tested

36 Silent Spring began the public debate over synthetic chemicalsRachel Carson’s Silent Spring (1962) showed DDT’s risks to people, wildlife, and ecosystems Gathered and presented scientific studies, medical cases, and other data Chemical companies challenged the book Attacked Carson’s science and personal reputation DDT was banned in the United States in 1973 But is still made in the United States and exported Used to control disease vectors in developing countries (reward is greater than risk) New technologies may stop disease without DDT

37 Not all toxicants are synthetic, and not all synthetic chemicals are toxicToxic chemicals also exist naturally and in our food It would be a mistake to assume natural chemicals are all healthy and synthetic ones are all harmful Plants produce toxic chemicals to defend themselves Most crop plants have had the level of toxic chemicals reduced by artificial selection, but not eliminated Eating animals may expose us to the plant chemicals they ate

38 Toxic substances come in different typesCarcinogens = substances that cause cancer Cells grow uncontrollably, damaging the body Prevalence of environmentally induced cancer has been underestimated Hard to identify because of the long time between exposure and onset of cancer and because not everyone exposed gets cancer Mutagens = substances that cause DNA mutations Most mutations have no effect, but some can cause cancer If they occur in sperm or eggs, can impact offspring

39 Toxic substances come in different typesTeratogens = chemicals that cause birth defects in embryos Thalidomide caused birth defects in the 1960s Neurotoxins = toxicants that assault the nervous system Animal venoms, heavy metals, pesticides, and chemical weapons

40 Toxic substances come in different typesAllergens = toxicants that overactivate the immune system Cause an immune response when one is not needed Increase in asthma in recent years may be due to increased prevalence of allergenic chemicals Not universally considered toxicants since they only affect some people and not others

41 Toxic substances come in different typesPathway inhibitors = toxicants that interrupt vital biochemical processes by blocking one or more steps in pathway The herbicide atrazine blocks steps in photosynthesis Endocrine disruptors = toxicants that affect the endocrine (hormone) system = chemical messenger system

42 Toxic substances come in different typesHormones stimulate growth, development, sexual maturity Work with extremely small concentrations Synthetic chemicals interfere with normal signals Block hormones, preventing signals from working Mimic hormones, causing a change Many mimic female sex hormones

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44 Organisms have natural defenses against toxic substancesOrganisms were exposed to toxic substances before humans starting producing them Heavy metals occur naturally; plants and animals produce toxic chemicals Exposure has driven selection for organisms that can tolerate these toxins Barriers (skin, scales, feathers) prevent uptake Biochemical pathways break down toxicants or are changed for easier excretion Some toxicants can not be broken down and are instead stored in fatty tissue (DDT) Defenses only work at low levels of toxicants

45 Individuals vary in their responses to hazardsDifferent 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

46 Individuals vary in their responses to hazardsThe Environmental Protection Agency (EPA) sets standards for responses based on adult responses Extrapolate adult responses to smaller size for children, infants Scientists argue that standards are not low enough to protect babies

47 The type of exposure affects the responseAcute exposure = high exposure to a hazard for short periods of time Easy to recognize Stems 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 due to time between onset of exposure and symptoms

48 Toxic Substances and Their Effects on EcosystemsToxicants concentrated in the environment can harm the health of many individuals of a species Population size decreases If the species is a predator, their prey may see population growth If the species is prey, its predator population may suffer Cascading impacts can cause changes in the composition of biological communities Can threaten ecosystem functioning

49 Airborne substances can travel widelyChemicals can travel by air Their effects can occur far from the site of use Synthetic chemicals are found globally Pristine lakes in the Canadian wilderness are contaminated with industrial toxicants

50 Airborne substances can travel widelyBecause of global air patterns, the poles are particularly contaminated with industrial toxicants Found in tissues of Arctic polar bears, Antarctic penguins, and people in Greenland Effects can occur over shorter distances Pesticide drift is the airborne transport of pesticides to land near agricultural fields

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52 Toxic substances may concentrate in waterToxic substances are not evenly distributed in the environment Move in specific ways Runoff carries toxins from land to surface water Chemicals in the soil can leach into groundwater, contaminating drinking water

53 Toxic substances may concentrate in waterChemicals enter organisms through drinking or absorption Aquatic organisms (fish, frogs, etc.) are good pollution indicators, giving early warnings of contamination Contaminants in streams and rivers enter drinking water and travel through the air

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55 Some toxicants persist in the environmentToxins 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 Many persistent chemicals are designed to last in the environment (paints, plastics)

56 Some toxicants persist in the environmentBreakdown 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

57 Toxicants may accumulate and move up the food chainToxicants in the body can be excreted, degraded, or stored Fat-soluble toxicants are stored in fatty tissues Bioaccumulation = process of toxicants building up in animal tissues to greater concentration than in the environment

58 Toxicants may accumulate and move up the food chainBiomagnification = process that occurs when concentrations of toxicants become magnified in higher levels of the food chain Each individual consumes multiple individuals from lower trophic levels, getting the toxicants from each Caused the near extinction of peregrine falcons and bald eagles from the 1950s to 1970s

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60 Toxic substances can threaten ecosystem servicesToxicants can alter the composition of ecosystems and species interactions Can threaten ecosystem services Pesticide exposure has been implicated in in declines of honeybee populations Honeybees pollinate over 100 economically important crops Decomposers and detritivores break down organic matter and improve soil Pesticides and antifungal agents may disrupt nutrient cycling

61 Wildlife studies integrate work in the field and labWild animals can serve as an early warning system for human health threats of toxicants in the environment Museum collections provide data from times before synthetic chemicals were used Can be used to assess changes seen today Measurements from animals in the wild can be compared to controlled experiments in the lab Work on alligators and frogs shows reproductive abnormalities due to endocrine disruption from pesticides and the herbicide atrazine

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63 Human studies rely on case histories, epidemiology, and animal testingCase histories = studies of individual patients; e.g., autopsies tell us about lethal doses Don’t tell about rare, new, or low-concentration toxins Don’t tell about probability and risk

64 Human studies rely on case histories, epidemiology, and animal testingEpidemiological studies = large-scale comparisons between exposed and unexposed groups 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

65 Human studies rely on case histories, epidemiology, and animal testingSince epidemiological studies can not establish causation, manipulative experiments are needed 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.

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67 Dose-response analysis is a mainstay of toxicologyDose-response analysis = testing method that measures the effect a toxicant produces or the number of animals affected at different doses 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 LD50/ED50 = the amount of toxicant required to kill (lethal dose) or show symptoms in (effective dose) 50% of the test subjects A high number indicates low toxicity

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69 Dose-response analysis is a mainstay of toxicologyThreshold dose = the level of toxicant where certain responses start to occur Organs can metabolize or excrete low doses of a toxicant; DNA damage can be repaired slowly Sometimes a response decreases as a dose increases U- or J-shaped or inverted-U curves Counterintuitive curves occur with endocrine disruptors The hormone system is geared to respond to minute concentrations (e.g., hormones) Scientists give large doses in animal studies and extrapolate downward to estimate the effect on humans

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71 Mixes may be more than the sum of their partsDetermining the impact of mixed hazards is difficult 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 New types of impacts may result from mixtures

72 Mixes may be more than the sum of their partsSynergistic 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 The interactive effects of most chemicals are unknown

73 Endocrine disruption pose challenges for toxicologyUnconventional 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 altering hormones Thousands of studies linked endocrine disruptors to effects on reproduction, development, immune functions, nervous systems, etc. Evidence is strongest in non-human animals Evidence in humans is growing Uncertainty in studying endocrine disruptors exists Negative findings pose economic threats to manufacturers

74 We express risk in terms of probabilityExposure 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, the chance and frequency of an encounter, and an organism’s exposure and sensitivity to the threat Probability = description of the likelihood of a certain outcome Risk = the probability that some harmful outcome will result from a given action, event, or substance

75 Our perceptions of risk may not match realityEvery action involves some element of risk We try to behave in ways that minimize risk, but perception may not match reality People worry about negligibly small risks while engaging in high-risk activities Flying is perceived as riskier than driving The chance of dying from an automobile accident is 73 times higher than in an airplane crash We feel more at risk when we do not control a situation We fear nuclear power and toxic waste But not smoking or overeating

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77 Risk assessment analyzes risk quantitativelyRisk assessment = the quantitative measurement of risk Compares risks involved in different activities or substances Identifies and outlines problems

78 Risk assessment analyzes risk quantitativelyRisk assessment has several steps. If assessing a chemical substance: Conduct a scientific study of toxicity Assess 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

79 Risk assessment analyzes risk quantitativelyEndocrine disruptors pose regulatory problems in relation to their risk assessment Scientific panels were convened to review research on BPA A government panel initially found that BPA posed an intermediate health risk Panel used mix of research with 70% coming from academic laboratories Industry protested that academic labs did not use the correct lab procedures Panel removed many academic studies and found no evidence of health impact

80 Risk management combines science and other socil factorsRisk management = decisions and strategies to minimize risk; encorporates results of risk assessment Federal agencies manage risk The United States has the Centers for Disease Control and Prevention (CDC), the EPA, the 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

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82 Two approaches exist for determining safetyWe can not know a substance’s toxicity until it is tested Two philosophies exist about determining safety The “innocent-until-proven-guilty” approach assumes a substance is harmless until shown to be harmful Helps technological innovation and economic advancement by limiting initial testing But allows dangerous substances to be used

83 Two approaches exist for determining safetyThe precautionary principle approach 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

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85 Philosophical approaches are reflected in policyDifferent nations use different policies for regulating synthetic substances Europe incorporates the precautionary principle The United States uses the innocent-until-proven-guilty approach But for some uses the precautionary principle is used 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

86 EPA regulation is only partly effectiveThe Toxic Substances Control Act (1976) directs the EPA to monitor thousands of chemicals made in or imported into the United States 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 the EPA can not do testing to show this 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

87 EPA regulation is only partly effectiveThe Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) 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 can be approved if economic benefits outweigh hazards

88 Toxicants are regulated internationallyThe EU’s REACH program (Registration, Evaluation, Authorization, and Restriction of Chemicals) shifts the burden of proof for safety to industry Precautionary principle Chemicals produced in amounts over 1 metric ton must be registered

89 Toxicants are regulated internationallyHelps industries research and develop safer products Chemicals will be approved, deemed unsafe, or tested further Estimated that 30,000 substances will be registered REACH will cost industry $3.8–7 billion over 11 years Health benefits will be $67 billion over 30 years

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91 Toxicants are regulated internationallyThe Stockholm Convention on Persistent Organic Pollutants (POPs) was enacted in 2004 and ratified by over 150 nations POPs = toxic, persistent chemicals that bioaccumulate and biomagnify and can travel long distances The Stockholm Convention sets guidelines for phasing out the “dirty dozen” = the 12 most dangerous POPs Encouraging transition to safer alternatives

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93 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 determines what policies are enacted A safe and happy future depends on knowing the risks some hazards pose and then replacing those substances with safer ones

94 QUESTION: Review Which of the following is a cultural hazard?Earthquake Smoking Viruses A pesticide All are cultural hazards. Answer: b

95 QUESTION: Review Toxicology isthe study of the effects of poisonous substances. any toxic substance. any substance that causes environmental degradation. the degree of harm a substance can cause. Answer: a

96 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 Answer: c

97 QUESTION: Review A “carcinogen” causes cancer. mutations.birth defects. problems in the hormonal system. Answer: a

98 QUESTION: Review A study that observes individual patients (e.g., autopsies) uses an epidemiological study. a case history approach. mainly private funding sources. probability and risk as major components of the study. Answer: b

99 QUESTION: Review Which statement about endocrine disruptors is NOT true? They may show unconventional dose-response curves. They affect reproduction, development, and immunity. It is easy to study their effects and show causation. The endocrine system is vulnerable to very low levels of these disruptors. Answer: c

100 QUESTION: Viewpoints Should the United States be able to manufacture and export chemicals that have been banned to use in the United States? No; if we won’t use 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. Answer: any

101 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. Answer: any

102 QUESTION: Interpreting Graphs and DataWhich of the following can we say about the rates of smoking and obesity in the United States based on this graph? Obesity has risen faster than smoking has declined. Decreased smoking has caused increased obesity. Obesity rates have fallen. There has been a 75% drop in smoking rates. Answer: a

103 QUESTION: Interpreting Graphs and DataIf 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. Answer: b