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

Damages Living Organism Degree of biological harm 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

Bioaccumulation/Biomagnification 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 Chemical 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 Radiation Thermal Particulates Asbestos EMF’s 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 Dose-Response Exposure 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 Response 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 Scientists perform animal tests 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 Public EPA, city, county Public Does weight of evidence justify a regulatory action Cost benefit analysis Risk benefit analysis Public preference