chapter 17
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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. - PowerPoint PPT PresentationTRANSCRIPT
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Chapter 17
Human Health and Environmental Risks
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What is Risk?
• Risk: possibility of suffering harm from a hazard
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Human Health Risks
• Physical• Biological• Chemical
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Leading Causes of Death Worldwide
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Biological Risks
• Disease: any impaired function of the body with a characteristic set of symptoms
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Biological Risks
• Infectious diseases: those caused by infectious agents, known as pathogens– Ex: pneumonia and
venereal diseases
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Pathogens• Bacteria:
– Cholera– Tuberculosis– Syphilis
• Virus:– HIV/AIDS– Hepatitis– Ebola
• Protozoa:– Malaria
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What causes disease?
• Infectious agents (pathogens) that spread by:– Air– Water– Food– Body fluids– Vectors (nonhuman carriers, like mosquitoes)
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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
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Leading Health Risks in the World
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Historical Diseases
• Plague• Malaria • Tuberculosis
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Emergent Diseases
• HIV/AIDS• Ebola• Mad Cow Disease• Bird Flu• West Nile Virus
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Emergent Diseases
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Pathways of Transmitting Pathogens
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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
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CigarettesEvery 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?
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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
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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”
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Dose-Response Studies
• LD50: the lethal dose that kills 50% of the individuals within a test population
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LD50
LD50 = 5.3
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Poisons
• Poisons: materials that kill at a very small dose (50 milligrams or less per kilogram of weight)
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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
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Threshold
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Dose-Response Studies
• ED50: effective dose that causes 50% of the individuals to display the harmful, but nonlethal, effect
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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
+ =
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Routes of Exposure
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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
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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
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Persistence• Persistence: how long a chemical remains in
the environment
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Risk Analysis
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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)
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Probabilities of Death in U.S.
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Risk Analysis
Risk =Probability of being exposed to a hazard
Probability of being harmed if exposedx
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Chemical Regulation
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Chemical Regulation
• Trade-off:– Greater safety with slower introduction of
beneficial chemicalsvs.
– Greater potential risk with a greater rate of discovery of beneficial chemicals