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© 2014 Pearson Education, Inc. Lecture Outlines Chapter 14 Environmental Health and Toxicology Withgott/Laposata Fifth Edition.

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Presentation on theme: "© 2014 Pearson Education, Inc. Lecture Outlines Chapter 14 Environmental Health and Toxicology Withgott/Laposata Fifth Edition."— Presentation transcript:

1 © 2014 Pearson Education, Inc. Lecture Outlines Chapter 14 Environmental Health and Toxicology Withgott/Laposata Fifth Edition

2 © 2014 Pearson Education, Inc. 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

3 © 2014 Pearson Education, Inc.

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  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 © 2014 Pearson Education, Inc. 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 © 2014 Pearson Education, Inc. We face four types of environmental hazards  Physical 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 © 2014 Pearson Education, Inc. We face four types of environmental hazards  Chemical 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

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11 We face four types of environmental hazards  Biological 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 © 2014 Pearson Education, Inc. We face four types of environmental hazards  Cultural 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 health  Despite 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 health  Where 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

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18 Social and environmental factors can influence the spread of infectious disease  Our 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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20 We are fighting disease with diverse approaches  One 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

21 © 2014 Pearson Education, Inc. We are fighting disease with diverse approaches  Education 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

22 © 2014 Pearson Education, Inc.

23 Toxicology is the study of chemical hazards  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

24 © 2014 Pearson Education, Inc. Toxicology is the study of chemical hazards  We 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

25 © 2014 Pearson Education, Inc. Many environmental health hazards exist indoors  Americans 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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27 Many environmental health hazards exist indoors  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

28 © 2014 Pearson Education, Inc. Many environmental health hazards exist indoors  Polybrominated 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

29 © 2014 Pearson Education, Inc. Risks must be balanced against rewards  As 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

30 © 2014 Pearson Education, Inc. Toxic Substances and Their Effects on Organisms  Toxins  toxic chemicals made in tissues of living organisms  Chemicals plants use to defend themselves  But synthetic chemicals are also in our environment  The United States makes or imports 113 kg (250 lb) of chemicals for every person in the country each year

31 © 2014 Pearson Education, Inc.

32 Synthetic chemicals are all around us—and in us  A 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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34 Synthetic chemicals are in all of our bodies  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  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

35 © 2014 Pearson Education, Inc. Toxic substances come in different types  Carcinogens  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

36 © 2014 Pearson Education, Inc. Toxic substances come in different types  Teratogens  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

37 © 2014 Pearson Education, Inc. Toxic substances come in different types  Allergens  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  Pathway inhibitors  toxicants that interrupt vital biochemical processes by blocking one or more steps in pathway  The herbicide atrazine blocks steps in photosynthesis

38 © 2014 Pearson Education, Inc. Toxic substances come in different types  Endocrine disruptors  toxicants that affect the endocrine (hormone) system  chemical messenger system  Hormones 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

39 © 2014 Pearson Education, Inc.


41 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

42 © 2014 Pearson Education, Inc. Individuals vary in their responses to hazards  The 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

43 © 2014 Pearson Education, Inc. The type of exposure affects the response  Acute 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

44 © 2014 Pearson Education, Inc.


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

47 © 2014 Pearson Education, Inc. Toxicants may accumulate and move up the food chain  Toxicants 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

48 © 2014 Pearson Education, Inc. Toxicants may accumulate and move up the food chain  Biomagnification  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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50 Toxic substances can threaten ecosystem services  Toxicants 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

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52 Human studies rely on case histories, epidemiology, and animal testing  Epidemiological 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

53 © 2014 Pearson Education, Inc. Human studies rely on case histories, epidemiology, and animal testing  Since 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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55 Dose-response analysis is a mainstay of toxicology  Dose-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  LD 50 /ED 50  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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57 Dose-response analysis is a mainstay of toxicology  Threshold 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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59 Mixes may be more than the sum of their parts  Determining 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  Synergistic effects  interactive impacts that are greater than the sum of their constituent effects  The interactive effects of most chemicals are unknown

60 © 2014 Pearson Education, Inc. 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, 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

61 © 2014 Pearson Education, Inc. Our perceptions of risk may not match reality  Every 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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63 Risk assessment analyzes risk quantitatively  Risk assessment  the quantitative measurement of risk  Compares risks involved in different activities or substances  Identifies and outlines problems

64 © 2014 Pearson Education, Inc. Risk assessment analyzes risk quantitatively  Risk 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

65 © 2014 Pearson Education, Inc. Risk management combines science and other socil factors  Risk 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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67 Two approaches exist for 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  The 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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69 Philosophical approaches are reflected in policy  Europe incorporates the precautionary principle  The United States 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

70 © 2014 Pearson Education, Inc. EPA regulation is only partly effective  The 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

71 © 2014 Pearson Education, Inc. Toxicants are regulated internationally  The 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

72 © 2014 Pearson Education, Inc. Toxicants are regulated internationally  Helps 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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74 Toxicants are regulated internationally  The 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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76 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 t hen replacing those substances with safer ones

77 © 2014 Pearson Education, Inc. QUESTION: Review Which of the following is a cultural hazard? a)Earthquake b)Smoking c)Viruses d)A pesticide e)All are cultural hazards.

78 © 2014 Pearson Education, Inc. QUESTION: Review Toxicology is a)the study of the effects of poisonous substances. b)any toxic substance. c)any substance that causes environmental degradation. d)the degree of harm a substance can cause.

79 © 2014 Pearson Education, Inc. QUESTION: Review Which of the following damages the brain and liver, causes learning problems, and comes from water flowing through certain pipes? a)Radon b)Asbestos c)Lead d)Polybrominated diphenyl ethers

80 © 2014 Pearson Education, Inc. QUESTION: Review A “carcinogen” causes a)cancer. b)mutations. c)birth defects. d)problems in the hormonal system.

81 © 2014 Pearson Education, Inc. QUESTION: Review A study that observes individual patients (e.g., autopsies) uses a)an epidemiological study. b)a case history approach. c)mainly private funding sources. d)probability and risk as major components of the study.

82 © 2014 Pearson Education, Inc. QUESTION: Review Which statement about endocrine disruptors is NOT true? a)They may show unconventional dose-response curves. b)They affect reproduction, development, and immunity. c)It is easy to study their effects and show causation. d)The endocrine system is vulnerable to very low levels of these disruptors.

83 © 2014 Pearson Education, Inc. QUESTION: Viewpoints Should the United States be able to manufacture and export chemicals that have been banned to use in the United States? a)No; if we won’t use it in the United States, we shouldn’t be able to make and export it to others. b)Yes, because the money we get from selling it will help our economy. c)Yes; let people decide what they want to do. d)Yes; in fact, chemicals should not be banned in the United States, either.

84 © 2014 Pearson Education, Inc. QUESTION: Viewpoints How should the U.S. government regulate chemicals? a)The government should force industries to prove their products are safe. b)The government should prove a chemical is dangerous before it is taken off the market. c)Industry knows chemicals best, so decisions such as this should be left up to the industry. d)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.

85 © 2014 Pearson Education, Inc. QUESTION: Interpreting Graphs and Data Which of the following can we say about the rates of smoking and obesity in the United States based on this graph? a)Obesity has risen faster than smoking has declined. b)Decreased smoking has caused increased obesity. c)Obesity rates have fallen. d)There has been a 75% drop in smoking rates.

86 © 2014 Pearson Education, Inc. 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? a)About 5 units b)About 10 units c)About 15 units d)You can’t tell from the graph.

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