1. AP Environmental Science CH. 19 - Risk, Toxicology
and Human Health
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2. Chapter Outline 1. Risks and Hazards 2. Toxicology 3. Chemical Hazards
definitions, major types
2. Toxicology
bioaccumulation, toxicity, dose–response curves
3. Chemical Hazards
mutagens, teratogens, carcinogens, hormone disrupters
4. Physical Hazards (NOT IN CHAPTER!)
earthquakes, volcanoes, ionizing radiation, EM radiation
5. Biological Hazards
diseases, controlling disease
6. Risk Analysis
how to estimate risk, major risks, managing risks
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3. 1. Risks and Hazards
Risk is the possibility of suffering harm from a hazard that can cause injury, disease, economic loss or environmental damage.
Risk is expressed as a probability
Risk assessment involves using data, hypotheses and models to estimate the probability of harm to human health, society, or the environment that may result from exposure to specific hazards
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4. Risk and Probability
Risk assessment
Fig p. 410
Risk management

5. Major Hazards There are 4 major types of hazards:
Cultural hazards- such as unsafe working conditions, smoking, poor diet, drugs, drinking, driving, criminal assault, unsafe sex and poverty
Chemical hazards from harmful chemicals in air, water, soil and food
Physical hazards- such as noise, fire, tornadoes, hurricanes, earthquakes, volcanic eruptions, floods and ionizing radiation
Biological hazards from pathogens, pollen and other allergens and animals, such as bees and poisonous snakes.
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6. Causes of Death
Tobacco use is the leading cause of preventable death (data from 1993).
Fig.19–1
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7. 2. Toxicology
Toxicology is the study of the adverse effects of chemicals on health.
Toxicity - a measure of how harmful a substance is
Dose- the amount of a potentially harmful substance that is ingested, inhaled, or absorbed through the skin
Response- the resulting type and amount of damage to health; two types of responses:
acute effect: immediate or rapid harmful reaction, e.g., dizziness, rash, death;
chronic effect: permanent or long–lasting consequence, e.g., asthma, kidney damage, heart disease;
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8. Fig. 19-3
Very
Insensitive

9. Bioaccumulation and Biomagnification
The pesticide DDT becomes increasingly concentrated high in the food chain because it is stored in fatty tissue and not easily broken down or excreted.
Bioaccumulation results when the concentration of a chemical in specific organs or tissues is higher than would normally be expected.
Biomagnification involves magnification of concentrations as they pass through the food chains and webs.
Fig.19–4
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10. Determining Toxicity 3 methods of determining toxicity:
Case reports: (usually to physicians) about health effects after exposure to a chemical
Epidemiology: involving studies of populations exposed to certain chemicals or diseases
Laboratory investigations: (usually with test animals)
LD50 is the median lethal dose = the amount of a chemical received that kills 50% of animals (usually rats or mice) in a test population (usually 60–200 animals) within a 14–day period
A poison is legally defined as a chemical that has an LD50 of 50 milligrams or less per kilogram of body weight.
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11. Poisons
Is this a poison?
What is the LD50?
See Table 19-5 p. 413

12. Some Toxicity Ratings Table 9–1 p.414
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13. Dose–Response Curves
Dose–response curves show the adverse effects of various doses of a toxic agent on a test population by plotting harmful effect as a function of dose.
The left dose–response curve shows increasing harmful effects with dose, and no dose is considered safe. The right example has a threshold, such that low doses are considered safe.
Fig.19–6
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14. 3. Chemical Hazards What are toxic vs. hazardous chemicals?
Toxic chemicals are generally defined as substances that are fatal to over 50% of test animals (LD50) at given concentrations.
Hazardous chemicals cause harm by
being flammable or explosive (e.g., gasoline);
irritating or damaging the skin or lungs (e.g., strong acids or alkalines such as oven cleaners);
interfering with or preventing oxygen uptake and distribution (e.g., carbon monoxide, CO);
inducing allergic reactions of the immune system (allergens).
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15. Mutagens, Teratogens, and Carcinogens
What are toxic vs. hazardous chemicals?
Mutagens are agents, chemicals and radiation, that cause random mutations, or changes in the DNA
Teratogens are agents (chemicals, radiation, or viruses) that cause birth defects;
e.g., PCBs, steroid hormones, heavy metals
Carcinogens are agents (chemicals, radiation, or viruses) that cause cancer;
over 100 types of cancer (depending on cells involved)
e.g., cigarette smoke.
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16. teratogens

17. Mutagens

18. Hormone Disrupters (Endocrine Disrupting Chemicals “EDC’s”)
Each type of hormone has a unique molecular shape that allows it to attach to special receptors of cells (upper left). Hormone mimics, such as estrogen-like chemicals, attach to receptors and disrupt normal activity (upper right). Hormone blockers prevent hormones such as androgen from attaching to receptors (lower).
Fig.19-7
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19. Hormone Disrupters
Hormones are molecules that act as messengers in the endocrine system to regulate various bodily processes, including reproduction, growth and development. Hormone disrupters interfere with hormone function.
So far 51 chemicals, many widely used, have been shown to act as hormone disrupters on wildlife, laboratory animals and humans;
e.g., dioxins, certain PCBs, various chemicals in plastics, some pesticides, lead and mercury;
1997 study shows that sperm count of men in U.S. and Europe has declined 50%.
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20. Readings on Endocrine Disrupters
4 summaries due Wednesday 3/3/10!

21. 4. Physical Hazards (not in this chapter!)
Earthquakes are among various types of natural physical hazards. Other physical hazards include volcanoes and ionizing radiation.
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22. Physical Hazards
For example, on October 17, 1989, a magnitude 7.1 earthquake along the San Andreas fault in California killed 67 people and caused about $10 billion in damage.
Fig.17–6
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23. Physical Hazards Map of expected damage from earthquakes.
Preventing loss:
understand where risk is high
establish building codes to regulate placement and design of buildings in high risk areas
determine if prediction is feasible.
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24. Physical Hazards
Ionizing radiation: a form of electromagnetic radiation, has enough energy to damage body tissues.
examples include X rays and ultraviolet radiation, and various types of radiation emitted by radioactive isotopes
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25. Physical Hazards
Each year people are exposed to some radiation from natural or background sources, as well as from human–caused exposure.
Background sources include about 82% of the exposure
Human–caused exposure include medical X rays (10%), nuclear medicine (4%), and consumer products (3%)
harmful effects include burns, miscarriages, eye cataracts and certain cancers
serious accidents, such as at the Chernobyl reactor, can release large quantities of radiation, far above background levels.
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26. Physical Hazards
Natural and human sources of the average annual dose of ionizing radiation received by the U.S. population. Most studies indicate that there is no safe dose of ionizing radiation.
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27. Physical Hazards Is non-ionizing electromagnetic radiation harmful?
We don't really know for sure!
Concern that electromagnetic fields (EMFs) from electrical appliances (e.g., microwave ovens, hair dryers, electric blankets, cell phones, computer and TV monitors) may increase risk of some cancers, miscarriages, birth defects and Alzheimer's disease
Many respected scientists say that a statistical link has between established, however, the evidence is still not conclusive.
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28. 5. Biological Hazards
Biological hazards include both non-transmissible and transmissible diseases.
Nontransmissible diseases are not passed from one person to another, e.g., cardiovascular disorders, most cancers, diabetes, emphysema and malnutrition
Transmissible diseases are caused by bacteria, viruses, protozoa, or parasites, and can be passed from one person to another, e.g., colds, flus, hepatitis, tuberculosis, sexually- transmitted diseases, malaria
some transmissible diseases are spreading over broad geographic areas as the result of human activity
e.g., Lyme disease carried by ticks and spread by people is now widespread over North America.
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29. Tuberculosis epidemic, kills about 2 million people a year.
Deaths per
100,000 people
<2.5
Deaths
2.5-10
Tuberculosis epidemic, kills about 2 million people a year.
10-35
35-70
70-100
100+

30. Biological Hazards
Worldwide distribution of malaria today (orange). If the world becomes warmer, as projected by current climate models, by 2046 malaria could affect 60% of the world’s population.
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31. Biological Hazards
For example, the complex life cycle of Plasmodium, the organism that causes malaria, involves transmission between infected individuals by Anopheles mosquitoes .
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32. 1918 epidemic killed 20-30 million
Greatest viral health threat to human life are emergent virulent flu strains…
1918 epidemic killed million
Today flu kills ~1 million per year (20,000 in the U.S.)
H1N1

33. Factors that affect the spread of transmissible diseases.
Increases international travel (H1N1)
Migration to urban areas
Migration to uninhabited areas and deforestation
Hunger and malnutrition
Increased rice cultivation
Global warming
Hurricanes and high winds
Accidental introduction of insect vectors
Flooding

34. Biological Hazards What are some ways we reduce infectious diseases?
Reduce overcrowding, unsafe drinking water, poor sanitation, inadequate health care systems, malnutrition and poverty
Increase funding for disease monitoring
Sharply reduce antibiotic use to prevent evolution of resistant organisms
Protect biodiversity as a means of reducing disease spread
Increase research- genetic pharming for vaccines
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35. 6. Risk Analysis
Risk analysis involves identifying hazards and evaluating associate risks (risk assessment), ranking risks (comparative risk analysis), determining options (risk management), and informing decision makers and the public (risk communication).
Risk assessment estimates probabilities associated with different types of hazards
Comparative risk analysis summarizes
the greatest ecological and health risks
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36. The Greatest Risks People Face
Poverty is the greatest risk by far
Poverty can lead to malnutrition, which can bring brings down the immunity and makes a path for other diseases to come in.
Also the greatest risks of premature death are mostly the result of careless mistakes.

37. Risk Analysis What are the greatest risks to humans in the U.S.?
Poverty poses the greatest risk (shortens lifespan by 7–10 years);
Smoking and being overweight pose the next greatest risk (each shortens lifespan by 6 years)
Being born male poses a greater risk than being female (shortens lifespan by 7.5 years)
Being unmarried is associated with risk (shortens lifespan by 5 years)
Other significant risks in the U.S. include second–hand smoke, driving, air pollution, alcohol use and drug abuse.
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38. Risk Analysis
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39. Proponents contend that risk analysis is a useful way to…
Organize and analyze available scientific information
Identify significant hazards
Focus on areas that warrant more research
Help regulators decide how money for reducing risks should be allocated,
Stimulate people to make more informed decisions about health and environmental goals and priorities.

40. How well do we perceive risks?
If chance of death is 1 in 100,000 people are not likely to be worried or change behavior.
Most of us do a poor job of assessing relative risks from hazards around us.
Most people deny the high-risk activities they voluntarily enjoy
Motorcycles (1 in 50)
Smoking (1 in 300 pack a day smokers, by 65)
Hang-gliding (1 in 2,500)

41. Yet some of these people are terrified of dying from…
Commercial plane crash (1 in 4.6 million)
Train crash (1 in 20 mil.)
Snakebite (1 in 36 mil.)
Shark attack (1 in 300 mil.)

42. Risk Analysis What are the limitations of risk assessment?
inaccuracy of models
inadequate data
bias because of who does the analyses
Major questions?
Which risks are worth evaluating?
How reliable are analyses?
How much risk is acceptable?
How much will it cost to reduce each risk?
How can a risk management plan be communicated?
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43. Risk Analysis Survey
Survey 12 people with their perceptions of various life risks.
Collect data and bring to class on Friday 3/5!