Presentation is loading. Please wait.

Presentation is loading. Please wait.

This lecture will help you understand:

Similar presentations

Presentation on theme: "This lecture will help you understand:"— Presentation transcript:


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


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


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 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 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 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


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 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


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


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


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


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 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


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 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 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


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 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 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 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


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


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 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 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 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 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



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 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 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



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 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 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


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


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 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.


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 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


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


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 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 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


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 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 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


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


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 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 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 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


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


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 then replacing those substances with safer ones

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

78 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. Answer: a

79 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

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

81 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

82 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

83 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

84 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

85 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? 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

86 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. Answer: b

Download ppt "This lecture will help you understand:"

Similar presentations

Ads by Google