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
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