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