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Chapter 17
Human Health and Environmental Risks
What is Risk?
• Risk: possibility of suffering harm from a hazard
Human Health Risks
• Physical• Biological• Chemical
Leading Causes of Death Worldwide
Biological Risks
• Disease: any impaired function of the body with a characteristic set of symptoms
Biological Risks
• Infectious diseases: those caused by infectious agents, known as pathogens– Ex: pneumonia and
venereal diseases
Pathogens• Bacteria:
– Cholera– Tuberculosis– Syphilis
• Virus:– HIV/AIDS– Hepatitis– Ebola
• Protozoa:– Malaria
What causes disease?
• Infectious agents (pathogens) that spread by:– Air– Water– Food– Body fluids– Vectors (nonhuman carriers, like mosquitoes)
Biological Risks
• Chronic disease: slowly impairs the functioning of a person’s body– Ex: heart disease, cancer, diabetes– 70% of all deaths in the U.S.
• Acute disease: rapidly impairs the functioning of a person’s body– Ex: Ebola hemorrhagic fever
Leading Health Risks in the World
Historical Diseases
• Plague• Malaria • Tuberculosis
Emergent Diseases
• HIV/AIDS• Ebola• Mad Cow Disease• Bird Flu• West Nile Virus
Emergent Diseases
Pathways of Transmitting Pathogens
Chemical Risks
• Neurotoxins: chemicals that disrupt the nervous system
• Carcinogens: chemicals that cause cancer• Teratogens: chemicals that interfere with the
normal development of embryos and fetuses• Allergens: chemicals that cause allergic
reactions• Endocrine disruptors: chemicals that interfere
with the normal functioning of hormones
Cigarettes
Every year, over 400,000 smokers and almost 40,000 non-smokers die from cigarette-related illnesses. In fact, smoking kills more people than HIV, drugs, alcohol, car crashes, and homicide combined. People who work in bars and restaurants, and those who live with smokers are especially at risk for secondhand-smoke related illness.
Should cigarettes be made illegal?
Toxicology Studies
• Retrospective studies– “Looking back” – Monitoring people who have already been
exposed to a chemical to determine the effects• Prospective studies
– “Looking forward”– Monitoring people who might become exposed to
a chemical to determine the effects
Toxicology
• Dose – the amount of a substance that a person has in their body– Can be:
• Ingested• Inhaled• Injected • Absorbed
• “The dose makes the poison”
Dose-Response Studies
• LD50: the lethal dose that kills 50% of the individuals within a test population
LD50
LD50 = 5.3
Poisons
• Poisons: materials that kill at a very small dose (50 milligrams or less per kilogram of weight)
Toxicity Rating LD50
Average Lethal Dose Examples
super toxic < 0.01 less than 1 drop nerve gases, botulism, mushroom toxins, dioxin
extremely toxic
< 5 less than 7 drops potassium cyanide, heroin, atropine, parathion, nicotine
very toxic 5–50 7 drop to 1 teaspoon
mercury salts, morphine, codeine
toxic 50–500 1 teaspoon to 1 ounce
lead salts, DDT, sodium hydroxide, fluoride, sulfuric acid, caffeine, carbon tetrachloride
moderately toxic
500–5,000 1 ounce to 1 pint methyl alcohol, ether, pehobarbital, amphetamines, kerosine, aspirin
slightly toxic 5,000–15,000 1 pint to 1 quart ethyl alcohol, lysol, soapsessentially nontoxic
> 15,000 more than 1 quart water, glycerin, table sugar
Threshold
Dose-Response Studies
• ED50: effective dose that causes 50% of the individuals to display the harmful, but nonlethal, effect
Interactions• Synergistic interactions: when two (or more)
risk factors have a greater effect together than each by themselves– Ex: being exposed to asbestos and smoking gives
you a 400 times greater chance of developing lung cancer than if you experienced only one of those risks
+ =
Routes of Exposure
Toxicology
• Solubility - what can the chemical dissolve in?– Water-soluble toxins– Oil/Fat-soluble toxins
• Which do you think is generally “better” for the health of an organism?– Water is “better” since it can be diluted– Fats aren’t good since chemicals can gather
in body fat of animals
Toxicology
• Bioaccumulation: an increased concentration of a chemical within an individual organism over time– The chemical is usually stored in
body fat • Biomagnification: the increase
in a chemical concentration in animal tissues as the chemical moves up the food chain
Persistence• Persistence: how long a chemical remains in
the environment
Risk Analysis
Qualitative vs. Quantitative
• Qualitative risk assessment: judging the relative risk of various decisions (ex: low, medium, or high)
• Quantitative risk assessment: determining the probability of an event occurring using data (ex: 83% chance)
Probabilities of Death in U.S.
Risk Analysis
Risk =Probability of being exposed to a hazard
Probability of being harmed if exposedx
Chemical Regulation
Chemical Regulation
• Trade-off:– Greater safety with slower introduction of
beneficial chemicalsvs.
– Greater potential risk with a greater rate of discovery of beneficial chemicals