Human Health and Environmental Risks

Many risk factors

Diseases

• Acute – Impair body rapidly– short in duration– Ebola, pneumonia

• Chronic– Slowly impair body over

decades– Heart disease, cancer,

lung disease, HIV/AIDS

toxicology

• Neurotoxins – EX: insecticides on insects, lead, mercury

• Carcinogens – cause cell damage and cause uncontrolled growth of these cells EX: asbestos, radon, formaldehyde, PCBs, vinyl chloride, chemicals in tobacco

• Teratogens – interfere with embryo/fetal development EX: thalidomide, alcohol

• Allergens – high response of immune system EX: peanuts, milk, penicillin, mold

• Endocrine disruptors – interfere with hormones EX: hormones from birth control pills/animal-rearing places in sewage, low sperm count in male fish and amphibians, DDT

Chronic disease risk factors• Differ between LDC and HDC. HOW?

• LDC associated with poverty: unsafe drinking water, poor sanitation, malnutrition

– ½ children under 5 that die from pneumonia is because of poor nutrition

– ¾ children who die from diarrhea suffer from poor nutrition

• HDC: tobacco, less active lifestyles, poor nutrition, overeating

Historically important infectious diseases

• Plague – bacteria transmitted by fleas• Malaria – protists transmitted by mosquito;

eradicated in US due to DDT• Tuberculosis – bacterial infection of lungs;

medicines not available/affordable in LDC– Drug-resistant strains

Emergent Infectious Diseases• Ability of many pathogens to mutate and be able to infect

humans• HIV/AIDS – combination antiviral drugs reduce virus gaining

resistant ($$, but changing)• Ebola hemorragic fever – virus, central Africa, 50-90% death

rate, no drugs, death in 2 weeks)• Mad Cow Disease – prions (proteins turned pathogens)• Bird Flu – not typically transmitted person to person, typically

only infects birds, but mutated• West Nile Virus – kills some birds, transmitted by mosquitoes,

causes brain inflammation, infect humans and horses

Future?• LDC : improve nutrition,

wider availability of clean drinking water, proper sanitation

• HDC: promotion of healthier lifestyle: increased physical activity, balanced diet, limit excess food consumption, and tobacco use

**All countries: continued education to reduce spread of HIV and TB

Determining the concentration of a chemical that is harmful

• LD50 – dose that kills 50% of test subjects– Unethical on humans; use mice/rats– Used to compare toxicity of different chemicals

• ED50 - dose that effects 50% of test subjects

challenges• Kids vs adults

• Synergistic interactions of chemicals – 2 risks together cause more harm than one would expect based on their individual risks– Health impact of a carcinogen, like asbestos, can be

much higher if an individual also smokes tobacco.

Risk analysis• Typically 3 steps:– Risk assessment• Identify hazard and determine extent of exposure

– Risk acceptance• Determine acceptable level of risk

– Risk management• Determine policy (with input from citizens, industry,

interest groups)

Risk analysis put into action…• Maker of electrical components dumped PCBs into Hudson

River• PCBs in air, soil, water and persist• EPA identified at what concentration PCB caused cancer

(LD50/dose-response)• Greater chance of getting cancer from eating contaminated

fish put up signs to minimize exposure

Perceived risk vs. actual risk

• Perceived (qualitative) / actual (quantitative)– Ex: someone afraid to fly in airplane, but will drive

car all the time.– Death in US:• 1. heart disease (1 in 5)• 2. cancer (1 in 7)• 3. COPD

ECONOMIC IMPACTS OF POLLUTION

• COST-BENEFIT ANALYSIS• EXTERNALITIES• MARGINAL COSTS• SUSTAINABILITY

• Economic activity generally harms the environment– Cost to environment not included in cost to buyer– External costs (externalities) are harmful social or

environmental effects caused by the production or consumption of economic goods• Buy cotton t-shirt at a price that doesn’t reflect

possible eutrophication due to fertilizer run-off or poor working conditions in “sweat shops.”• Ex: paper manufacturer dumps wastes into local river

(public goods) negative impacts on fish that depend on water, decrease quality of water used for recreation, extensive treatment of water to drink downstream

Cost-benefit analysis• Cost-benefit analysis looks at the social benefits

(health/environmental) that can be derived from pollution reduction vs the cost of achieving that reduction. – There is a limit to how much money can be spent before the budgets

of other important public services (police, fire, parks departments) are negatively impacted.

– As hazards become more known, perceived benefits derived from pollution reduction may increase.

– Problem with analysis: assumes all benefits have a price tag. Aesthetic benefits cannot be prices and are important (beauty of a clear-running stream and quiet solitude of a wilderness)

Marginal costs

• The change to the total cost when the quantity produced changes by one unit.

• Marginal cost of pollution abatement: Initial clean-up of a polluted site is cheap, but gets increasingly more costly

Sustainability• Seek to proved best outcomes for both human societies

and natural ecosystems.– Conservation of biodiversity and ecological integrity– Integration of environmental, social, and economic goals in

policies and activities– Need for good governance

• Unlimited economic and population growth puts many demands on natural resources.