1. AP Environmental Science Risk, Toxicology and Human Health
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2. 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
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 expressed as a probability;
1 in 250
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;
risk management involves deciding how or whether to reduce a possible risk to a certain level and at what cost.
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4. Major Hazards There are four 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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5. Causes of Death
Tobacco use is the leading cause of preventable death (data from 1993).
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6. 2. Toxicology
Toxicology is the study of the adverse effects of chemicals on health.
toxicity is a measure of how harmful a substance is. Toxicity depends on several factors;
the amount of a potentially harmful substance that is ingested, inhaled, or absorbed through the skin is called the dose;
frequency of exposure;
who is exposed (adult or child);
how well the body’s detoxification system (liver, lung, kidneys, etc.) work
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7. Toxicology
The resulting type and amount of damage to health are called the response
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;

8. Toxicology
Five major factors can determine the harm caused by a substance
Solubility
water-soluble toxins move through the environment and get in the water supply
fat-soluble toxins can penetrate cell membranes and accumulate in body tissue
Persistence
some chemicals are resistance to breakdown and have long-lasting harmful effects on people and wildlife
Bioaccumulation and biomagnification
see next slide

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.
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10. Toxicology Chemical Interactions
antagonistic interactions reduce harmful effects
Vitamin A and E apparently reduces some cancer-causing chemicals
synergistic interactions multiplies harmful effects
asbestos workers have a 20-fold increased chance of getting lung cancer, but if they smoke they have a 400-fold increased in lung cancer rate

11. Determining Toxicity
Toxin or poison is a chemical that adversely affects the health of a living human or animal by causing injury, illness, or death
Three 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.

12. Toxicity Toxicity LD50 Lethal Dose Examples
Super < 0.01 less than 1 drop dioxin, botulism
mushrooms
Extreme <5 less than 7 drops heroin, nicotine
Very drops to 1 tsp morphine, codeine
Toxic tsp DDT, H2SO4, Caffeine
Moderate K 1 oz.-1 pt aspirin, wood alcohol
Slightly 5K-15K 1 pt ethyl alcohol, soaps
Non-Toxic >15K >1qt water, table sugar
***Higher LD50, less toxic the substance is
(LD50 measured in mg/kg of body weight)

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.
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14. Why so little is known of toxicity
Only 10% of at least 75,000 commercial chemicals have been screened
~2% determined to be carcinogen, teratogen or mutagen
>1000 new synthetic chemicals added per year
>99.5% of US commercial chemicals are NOT regulated

15. 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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16. 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; rubella, mercury in water, fetal alcohol syndrome and crack babies
carcinogens are agents (chemicals, radiation, or viruses) that cause cancer;
over 100 types of cancer (depending on cells involved);
e.g., cigarette smoke.
hormone disrupters
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17. Hormone Disrupters
Each type of hormone has a unique molecular shape that allows it to attach to special receptors of cells (upper left).
Hormone disrupters (mimics and blockers), attach to receptors and disrupt/alter development (upper right).
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18. Hormone Disrupters
Hormones are molecules that act as messengers in the endocrine system to regulate 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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19. Taking Precautions Precautionary Principle:
New chemicals and technologies would be assumed to be harmful until shown otherwise
Existing chemicals and technologies should be removed from the market until their safety can be established
Strictly applied precautionary principle would not have given us automobiles, antibiotics, and plastics.
No easy answer for knowing when to apply precautionary principle

20. 4. Physical Hazards
Earthquakes are among various types of natural physical hazards. Other physical hazards include volcanoes and ionizing radiation.
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21. 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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22. 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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23. 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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24. 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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25. Physical Hazards Is non-ionizing electromagnetic radiation harmful?
we don't know
concern that electromagnetic fields (EMFs) from electrical appliances (e.g., microwave ovens, hair dryers, electric blankets, 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, but the evidence is still not conclusive.
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26. 5. Biological Hazards
Biological hazards include both non-transmissible and transmissible diseases.
non-transmissible 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, 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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28. Biological Hazards
Worldwide distribution of malaria today (red) and its projected distribution in 2046 (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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29. Biological Hazards
The complex life cycle of Plasmodium, the organism that causes malaria, involves transmission between infected individuals by Anopheles mosquitoes .
Malaria Video
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30. 7 Deadliest Infectious Diseases

31. Case Study: Growing Germ Resistance to Antibiotics
1 bacteria can produce 16,777,216 offspring in 24 hours
this allows them to become genetically resistant to antibiotics through natural selection
Other factors that play a role in the increase in serious infectious bacterial diseases;
bacteria is spread around the globe by human travel and trade goods
overuse of pesticides
overuse of antibiotics

32. Case Study: Growing Germ Resistance to Antibiotics
Overuse of antibiotics
½ of all antibiotics are prescribed unnecessarily
antibiotics are available is some countries without a prescription
In the U.S., 75% of all antibiotics used are fed to livestock as feed additives to boost production.
resistant strains of infectious disease can spread to humans through contact with infected animals
Every major disease-causing bacterium now has strains that resist at least one of the roughly 160 antibiotics used to treat bacterial infections.

33. Case Study: The Global Tuberculosis Threat
TB kills about 1.7 million people a year and could kill 28 million by 2020
The bacterium causing TB moves from person to person in airborne droplets by sneezing, singing, or talking.
it has infected 1 in 3 people in the world
it in the body, whether you are sick or not
over ½ the infected people do not know they are infected and do not feel sick
silent global epidemic

34. Case Study: The Global Tuberculosis Threat
Increase in TB caused by
lack of screening and control programs
resistance to almost all effective antibiotics
population growth and urbanization causes increased contact between people, especially among the poor
AIDS weakens immune system and allows TB to multiply
Can be cured by a combination of 4 inexpensive drugs
must be taken daily for 6-8 months
symptoms disappear, people think they are cured and stop taking their medicine
this cause the disease to recur in a drug-resistant form
TB Evolution Movie

35. HIV, Flu, and Hepatitis B
HIV (human immunodeficiency virus) transmitted by
unsafe sex, sharing of needles by drug users, infected mother to offspring before or after birth, and exposure to infected blood.
Influenza (flu) is transmitted by
body fluids
airborne emissions of infected persons
1918 Swine Flu
Killed 500 million worldwide
million in the U.S.
Today flu kills
1 million per year worldwide
20,000 in the U.S.

36. HIV, Flu, and Hepatitis B
Hepatitis B virus (HBV) damages the liver and is transmitted by
unsafe sex, sharing of needles by drug users, infected mother to offspring before or after birth, and exposure to infected blood,
Other viruses that have received widespread coverage
Ebola virus transmitted by blood or other body fluids
West Nile virus transmitted by mosquitoes that have been feeding on infected birds
Severe Acute Respiratory Syndrome virus (SARS) emerged in China in 2002 and is easily transmitted.
Uganda: Out of the Wild

37. HIV, Flu, and Hepatitis B
Viral infections are harder to fight than infections caused by bacteria and protozoa.
drugs that kill viruses also harm the cells of the host
antibiotics are useless and increase genetic resistance in bacteria
vaccines that stimulate the immune system to produce antibodies to ward off viral infections and help reduce the spread of viral diseases
polio, influenza, measles, smallpox, rabies, and hepatitis B.
many viral diseases do not have vaccines
HIV

38. Biological Hazards
Generalized model of the epidemiological transition that may take place as countries become more industrialized.
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39. 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.
careful hand washing

40. 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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41. Risk Analysis