1. 10 Environmental Health and Toxicology PowerPoint® Slides prepared by
Jay Withgott and April Lynch

2. This lecture will help you understand:
Environmental health hazards
Environmental health goals
Synthetic and natural toxicants
The study of hazards and their effects
Risk assessment and risk management
Policy and regulation

3. Central Case: Alligators and Endocrine Disruptors at Lake Apopka, Florida
Biologist Louis Guillette found alligators with reproductive abnormalities in a Florida lake.
The lake had been contaminated with pesticides.
Research revealed that chemicals in the lake were disrupting the animals’ reproductive hormones.

4. Environmental health
Assesses environmental factors that influence human health and quality of life
Seeks to prevent adverse effects on human health and ecological systems
Contains environmental toxicology within its scope

5. Environmental health hazards
Types include:
• Physical hazards (floods, blizzards, landslides, radon, UV exposure)
• Chemical hazards (disinfectants, pesticides)
• Biological hazards (viruses, bacterial infections)
• Cultural or lifestyle hazards (drinking, smoking, bad diet, crime in neighborhood)

6. Environmental health hazards
LE 10-1
Physical hazard
Chemical hazard
Biological hazard
Cultural hazard

7. Infectious disease
In communicable or transmissable disease, a pathogen attacks a host,
either directly or through a vector (e.g., mosquito that transfers a malaria parasite to hosts)
… and the pathogen can be transmitted from one host to another.
Infectious disease causes 25% of deaths in the world
and nearly half of deaths in developing nations.

8. Annual deaths (millions)
Infectious disease
LE 10-2
4.0
Respiratory and
digestive diseases
Other
3.5
3.0
Maternal
and
perinatal
conditions
7.9%
2.5
10.0%
Infectious
diseases
14.9 million
26.1%
Annual deaths (millions)
2.0
5.2%
1.5
9.1%
Injuries
Cardiovascular
diseases
29.3%
1.0
12.5%
0.5
Cancers
Respiratory
infections
(influenza,
pneumonia, etc.)
AIDS
Diarrheal
diseases TB
Malaria
Childhood
diseases
(measles,
Pertussis,
tetanus, etc.)
Leading causes of death across the world, 2004
Leading causes of death by infectious disease, 2004

9. Many health hazards also exist indoors
Substances in plastics and consumer products
Lead in paint and pipes
Radon
Asbestos
PBDE fire retardants

10. Toxicology
…is the study of poisonous substances and their effects on humans and other organisms.
Toxicologists assess and compare toxic agents, or toxicants, for their toxicity, the degree of harm a substance can inflict.
Environmental toxicology focuses on effects of chemical poisons released into the environment.

11. Environmental toxicology
Toxicants are studied that come from or are discharged into the environment and their:
Health effects on humans
Effects on animals
Effects on ecosystems
Animals are studied:
For their own welfare
As “canaries in a coal mine” to warn of effects on humans

12. Synthetic chemicals are everywhere in our environment
Many thousands have been produced and released.
Some persist for long time periods or travel great distances.
Of the 100,000 synthetic chemicals on the market today, very few have been thoroughly tested for harmful effects.
2002 USGS study: 80% of U.S. streams contain up to 82 wastewater contaminants, including antibiotics, perfumes, detergents, drugs, steroids, disinfectants, and so forth.

13. Rise of synthetic chemicals
There has been widespread synthetic chemical production since WWII.
People were largely unaware of the health risks of many toxicants.
The potent insecticide DDT was sprayed widely in public areas, even on people.

14. Silent Spring and Rachel Carson
Carson’s 1962 book alerted the public that DDT and other pesticides could be toxic to animals and people.
Further research led the EPA to ban DDT in 1973.
These developments were central to the modern environmental movement.

15. Types of toxicants Carcinogens: cause cancer
Mutagens: cause mutations in DNA
Teratogens: cause birth defects
Allergens: cause unnecessary immune response
Neurotoxins: damage nervous system
Endocrine disruptors: interfere with hormones

16. Endocrine disruption
Some chemicals, once inside the bloodstream, can “mimic” hormones.
If molecules of the chemical bind to the sites intended for hormone binding, they cause an inappropriate response.
Thus these chemicals disrupt the endocrine (hormone) system.

17. Normal hormone binding
LE 10-4
Hormone
Response
Receptor
Cell membrane
Inside cell
Normal hormone binding
Hormone mimic
Hormone
Response
(identical
to that
caused by
hormone)
Receptor
Cell membrane
Inside cell
Hormone mimicry

18. Endocrine disruption
The hormone system is geared to working with tiny concentrations of hormones …
… so, it can respond to tiny concentrations of environmental contaminants.
Have chemicals in the environment acted as endocrine disruptors in humans?

19. Frogs, people, and atrazine
Frogs show reproductive abnormalities in response to small doses of the herbicide atrazine, researcher Tyrone Hayes has found.
Others suggest that atrazine may have effects on humans as well.
The fierce criticism from atrazine’s manufacturer reflects the high stakes in environmental toxicology.

20. Declining sperm counts?
A 1992 study summarized results of sperm count studies worldwide since Data showed a significant decrease in men’s sperm counts over 50 years.

21. Declining sperm count in humans, based on 61 studies
LE 10-6a
Declining sperm count in humans, based on 61 studies

22. Testicular cancer
Others hypothesize that endocrine disruptors are behind the rise in testicular cancer in many nations.

23. Increasing incidence of testicular cancer
LE 10-6b
Denmark
Norway
Germany
Sweden
Finland
Estonia
Increasing incidence of testicular cancer

24. Toxicants move in specific ways
Synthetic chemicals take many routes in traveling through the environment.

25. Industry and manufacturing Human fetuses and babies
LE 10-7
Industry and manufacturing
Consumer products
Medicines and
materials
Pesticides and
fertilizers
Waste
Waste
Waste
Workplace products
Medical facilities
and public spaces
Agriculture: crops,
rangeland, feedlots
Water: surface
and groundwater
Home
Work
Soil
Air
Workplace exposure
Medicines and
materials
Food
Consumer products
Plant growth
Drinking water
Air for breathing
Drinking water
Non-target effects
Air for breathing
Humans
Hunting and
harvesting
Genes, womb,
breast milk
Non-human biota
Human fetuses and babies

26. Toxicants concentrate in water
Surface water and groundwater can accumulate toxicants.
Runoff from large areas of land drains into water bodies, becoming concentrated.
Toxicants in groundwater or surface water reservoirs used for drinking water pose potential risks to human health.

27. Airborne toxicants
Volatile chemicals can travel long distances on atmospheric currents.
PCBs are carried thousands of miles from developed nations of the temperate zone up to the Arctic, where they are found in tissues of polar bears and seals.

28. Persistence
Some chemicals are more stable than others, persisting in the environment.
DDT and PCBs are persistent.
Bt toxin in GM crops is not persistent.
Temperature, moisture, sun exposure, and so forth, affect the rate of degradation.
Most toxicants degrade into simpler breakdown products. Some of these are also toxic.
(DDT breaks down to DDE, also toxic.)

29. Poisons accumulate in tissues
The body may excrete, degrade, or store toxicants.
Fat-soluble ones are stored.
DDT is persistent and fat soluble,
… so it builds up in tissues: bioaccumulation.
Bioaccumulated chemicals may be passed on to animals that eat the organism—up the food chain…

30. Poisons move up the food chain
At each trophic level, chemical concentration increases: biomagnification.
DDT concentrations increase from plankton to fish to fish-eating birds.

31. LE 10-8
DDT concentration
(parts per million)
Osprey
25 ppm
Large fish
2 ppm
Small fish
0.5 ppm
Zooplankton
0.04 ppm
Water
ppm

32. Not all toxicants are synthetic
Although toxicology tends to focus on man-made chemicals, it’s important to keep in mind that there are plenty of natural toxicants.
Many are toxins produced by animals or plants for protection against predators and pathogens.

33. Studying effects of hazards
Toxicologists study effects in several major ways:
• Wildlife toxicology studies
• Human epidemiological studies
• Dose-response studies in the lab

34. Approaches in environmental health research
Human studies rely on:
Case history = observation and analysis of individual patients
Epidemiological studies = long-term, large-scale comparisons of different groups of people
Animal testing

35. Epidemiology Advantages: Realistic All real-life factors included
Disadvantages: Statistically correlational only; does not prove causation
Takes many years to get results

36. Mixing toxicology with anthropology
Mexican children were tested for pesticide effects.
From The Science behind the Story

37. Drawings by children in the foothills
LE 10-SBS
4-year-olds
5-year-olds
Drawings by children in the foothills
4-year-olds
5-year-olds
Drawings by children in the valley

38. Dose-response analysis
Dose-response analysis is a method of determining the toxicity of a substance by measuring response to different doses.
Lab animals are used.
Mice and rats breed quickly and give data relevant to humans because they share mammal physiology with us.
Responses to doses are plotted on a dose-response curve.

39. Dose-response curve LD50 = dose lethal to 50% of test animals
Threshold = dose at which response begins

40. Dose-response curve
Dose-response curves allow us to predict effects of higher doses.
By extrapolating the curve out to higher values, we can predict how toxic a substance may be to humans at various concentrations.
In most curves, response increases with dose.
But this is not always the case; the increase may not be linear.
With endocrine disruption, it may decrease.

41. Factors affecting toxicity
Not all people are equal. Sensitivity to a toxicant can vary with sex, age, weight, and so forth.
Babies, older people, or those in poor health are more sensitive.
Type of exposure:
acute = high exposure in short period of time
chronic = lower amounts over long period of time

42. Mixtures of toxicants Substances may interact when combined together.
Mixes of toxicants may cause effects greater than the sum of their individual effects.
These are called synergistic effects.
A challenging problem for toxicology: There is no way to test all possible combinations!
(And the environment contains complex mixtures of many toxicants.)

43. Risk
Risk = the mathematical probability that some harmful outcome will result from a given action, event, or substance
Probability = a quantitative description of the likelihood of a certain outcome
“Harmful outcome” could be defined as injury, death, environmental damage, or economic loss

44. Perception differs from reality
Our perception of risks tends not to match statistical reality.
smoking
plane crash

45. Risk assessment Analyzes risks quantitatively
Measures and compares risks involved in different activities or substances
Helps identify and prioritize serious risks
Helps determine threats posed to humans, wildlife, and ecosystems

46. Risk management
Considers risk assessments in light of social, economic, and political needs and values
Weighs costs and benefits, given both scientific and nonscientific concerns
Results in decisions whether or not to reduce or eliminate risk

47. Risk assessment and risk management inform policy
Following risk management, policy decisions are made.

48. ethical considerations
LE 10-11
Scientific results
and measurement
of probability
Political, social,
economic, and
ethical considerations
Risk
assessment
Risk
management
Policy
Scientific data on
Information, opinion, and lobbying from
Hazard
identification
Toxicity
character-
ization
Extent of
exposure
Private
citizens
Industry and
manufacturing
Nonprofit
Interest
groups

49. Philosophical approaches
“Innocent until proven guilty”:
Assume harmless until shown to be harmful
Precautionary principle:
Assume harmful until shown to be harmless

50. Implications for product testing
“Innocent until proven guilty”:
Industry can introduce any products it wants.
Government bears the burden of proof to show if products are dangerous.
Precautionary principle:
Industry cannot introduce a product until it is very thoroughly tested and shown convincingly to be harmless.

51. Implications for product testing
Industry has pressured government to take an “innocent-until-proven-guilty” approach.
Environmental advocates have pressured government to follow the precautionary principle.

52. “Innocent until proven guilty” approach Precautionary
LE 10-12
“Innocent until proven
guilty” approach
Precautionary
principle approach
Sequence of events
Industrial research and
development
Pre-market testing by
industry, government,
and academic
scientists
Limited testing; all
products brought to market
Rigorous testing; only the safest
products brought to market
Consumer use of
products
Some products harm
human health
Minimal impact on
human health
Post-market testing by
industry, government,
and academic scientists
Rigorous testing demanded
Limited testing required
Regulations and bans
of unsafe products
Unsafe products recalled
Consumer use of safe
products

53. Federal agencies and risk management
In the United States, most risk management is conducted by federal and state agencies.
Particularly:
Environmental Protection Agency
and
Food and Drug Administration

54. Policy on toxicants Key agencies and products they regulate:
Food and Drug Administration (FDA)
food, additives, cosmetics, drugs, medical devices
Environmental Protection Agency (EPA)
pesticides, industrial chemicals, and any synthetic chemicals not covered by other agencies
Occupational Health and Safety Administration (OSHA)
workplace hazards

55. EPA regulation: Pesticides
Pesticides to be introduced to market in the United States need to be registered with the EPA.
Registration involves risk assessment and risk management.
The EPA assesses research from the manufacturer along with any outside research.
The EPA can set restrictions on use, or even ban a product.

56. EPA regulation: Industrial chemicals
The EPA is charged with monitoring 75,000 industrial chemicals.
There are too many chemicals and not enough time, people, or resources.
Only 10% of chemicals on the market are thoroughly tested.
Only 2% are screened for carcinogens, mutagens, and teratogens.
<1% are government regulated.
~0% are tested for endocrine, nervous, or immune effects.

57. International policy on toxicants
The EU has proposed legislation to require 30,000 chemicals to be tested and registered, and 1,500 hazardous chemicals to be restricted.
Stockholm Convention, 2001: international treaty to phase out 12 persistent organic pollutants (POPs), “the dirty dozen”

58. Viewpoints: Industry or government?
Warren Porter
Marian Stanley
“Given the inherent inadequacies of the testing process and the uncertainty of the economic impacts, both government and industry should share the responsibility of testing to ensure public safety.”
“Manufacturers often voluntarily conduct new studies to support the continued safe use of their chemicals. … It is important that the EPA and manufacturers work together in evaluating chemicals.”

59. Conclusion
International agreements are a hopeful sign that governments will control environmental hazards.
But solutions may come more easily when they do not arise from government regulation alone.
Consumer choice can influence industry if consumers have accurate information.
But we will never attain complete knowledge of risks.
A safer future depends on knowing risks, phasing out harmful substances, and replacing them with safer ones.

60. QUESTION: Testing Your Comprehension
Which causes birth defects?
a. Allergen
b. Mutagen
c. Carcinogen
d. Teratogen
e. Endocrine disruptor

61. QUESTION: Testing Your Comprehension
Which causes birth defects?
d. Teratogen

62. QUESTION: Testing Your Comprehension
Which statement is NOT correct regarding the insecticide DDT?
a. It was criticized in the book Silent Spring.
b. It helps fight malaria.
c. It is persistent and bioaccumulates.
d. It has no toxic breakdown products.
e. Its use was banned by the EPA.

63. QUESTION: Testing Your Comprehension
Which statement is NOT correct regarding the insecticide DDT?
d. It has no toxic breakdown products.

64. QUESTION: Testing Your Comprehension
Epidemiological studies… ?
a. Can prove a certain toxicant causes a certain effect.
b. Search for statistical association between hazard and effect.
c. Are rapidly completed.
d. Take place with lab animals.

65. QUESTION: Testing Your Comprehension
Epidemiological studies… ?
b. Search for statistical association between hazard and effect.

66. QUESTION: Testing Your Comprehension
Which statement is FALSE?
a. Babies are more sensitive to toxicants than 30- year-olds.
b. Synergistic effects can occur with mixtures of chemicals.
c. Chronic exposure occurs over a short period of time.
d. Some doses may elicit no measurable response.

67. QUESTION: Testing Your Comprehension
Which statement is FALSE?
c. Chronic exposure occurs over a short period of time.

68. QUESTION: Seeking Solutions
Describe some environmental hazards you think you may be living with indoors. How do you think you may have been affected by indoor or outdoor environmental hazards? What steps do you plan to take to deal with these toxicants in your own life?

69. QUESTION: Seeking Solutions
Do you feel laboratory-bred animals should be used in experiments on toxicology? Why or why not? Can you envision any alternatives?

70. QUESTION: Viewpoints
In testing new synthetic chemicals, should we follow the “innocent-until-proven-guilty” approach, or the precautionary principle?
a. “Innocent-until-proven-guilty” approach
b. Precautionary principle
c. A hybrid of both approaches