Environmental Hazards & Human Health

Environmental Hazards

• Complex interactions– Biosphere, atmosphere, hydrosphere,

lithosphere

• Industrialized Societies– Generate & dump huge amount of

pollutants/toxic wastes

• Agents– Biological, chemical, physical

• Effects– Acute– Chronic

• Toxin– Inhaled, ingested, absorbed

• Sufficient Dosage• Damages Living Organism• Degree of biological harm• How do we determine toxicity?

Environmental Toxicology• Study of effects of chemical, physical

& biological agents • Help policymakers– Determine costs & benefits–What affect they have

• Complicated–Many stressors in environment– System must evaluated for an extended

period of time–Must be clear to evaluate

Toxicity

• Depends on– Dose– Exposure–Who (adult vs. child)– How well does body’s detox work• Liver, kidneys, lungs

– Genetics– Solubility• Fat vs. water

– Persistence– Bioaccumulation/Biomagnification• Move through food web• Accumulate or increase concentration

– Chemical Interactions• Synergy

Difficult, Costly & Controversial

• Estimating toxicity levels & risks have serious limitations

• Analysts work with available info which never seems sufficient– Only 10% of 85,000 synthetic chemicals

are registered– Only 2% have be adequately tested

• Teratogen, mutagen, carcinogen

–Most chemicals are considered innocent until proven guilty

Pollutants

• Biological or infectious– Bacterial, fungi, viruses– TB, malaria, AIDS

• Chemical– Heavy metals (Hg, Pb, Cd, As, Cr)– Organic compounds• Food additives, pharmaceuticals• 20 million synthetic chemicals

– POP’s – persistent organic pollutants• PCB’s, dioxin, DDT, Aldrin, Dieldrin

– Endocrine disruptors• DDT, Phthalates, PCB’s

– Radiation– Thermal– Particulates

• Dust, soot, asbestos fibers

– Asbestos– EMF’s

• Transmission wires

– Noise– Cultural

• Smoking, sunbathing, drug abuse, risky sexual behavior

Risk Assessment & Management

• What is the hazard?• Probability of risk?• Consequence of risk?• Risk Assessment is– Process of evaluating the risk(s)

associated with a hazard– Difficult, costly & controversial

Risk Assessment

• ID Hazard– Testing– Statistical analysis

• Dose-Response– Relationship between dose & health

effect

• Exposure– Intensity, duration & frequency

• Risk Characterization– Delineate health risk– Potential of health problem– Evaluate testing results

Dose-Response• Measure of Toxicity• Dose– The amount that enters the body– Lethal doses vary depending on age,

sex, health, metabolism, and genetic makeup

• Response– The type & amount of damage that

exposure to a particular dose causes

Testing

• Epidemiology– Study of populations & their exposure to

certain chemicals and/or patterns of toxicity

• Scientists perform animal tests• LD50 lethal dose to 50% of population

– Mass of dose/Kg of body weight– The smaller the LD50 the greater the toxicity

• TD50 threshold dose to 50% of population– Dose induces effects

Dose-Response Curve

• Graph that relates amount of substance with the response– X-axis is amount or dose of substance– Y-axis is the response

• Threshold Dose– Point on graph where response is first

observed

Risk Management

• Deciding whether or how to reduce a risk– Thorough review of information– How does it compare with other risks– How should it be reduced– Reduction strategy– Cost

Who Makes Decision?

• Law makers & administrators– EPA, city, county

• Public • Does weight of evidence justify a

regulatory action– Cost benefit analysis– Risk benefit analysis– Public preference