Chapter 4 Risk Analysis, Environmental Health Hazards, and Toxicology
A Perspective On Risks
Human health has improved Longer life span Risk Probability of harm occurring in certain circumstances Part of daily life Must understand nature and size of risk
Probabilities Of Risk
Probability of 1 ---> risk certain to occur Probability of 0 ---> risk certain not to occur
Risk Assessment
Quantifying risks of an action Four steps 1) Hazard identification 2) Dose-response assessment 3) Exposure assessment 4) Risk characterization Evaluate results
Risk Assessment
Choose Your Risk
No choice for some risks What risks do we worry most about? Why do we choose risky behavior?
Environmental Health Hazards
We are exposed to many chemicals Toxicology Study of harmful contaminants Acute toxicity Chronic toxicity Pathogens Bacteria Fungus Virus
Polluted Water
Water is tested for presence of pathogens Fecal coliform test
E. coli
Filter water Let bacteria grow Count bacterial colonies
Water And Disease
Environmental Change & Disease
Epidemiologists Links between human health and environmental change Deforestation, dams, agriculture How do these cause more disease? Social factors Travel
Malaria
Transmitted by Anopheles mosquitoes Cut down forests ---> more pools of water ---> more mosquitoes Peru, Bangladesh, Amazon Climate change also a factor
Malaria & New Technology
Satellite images Chiapas, Mexico Images show areas at risk Target those areas
Toxicants In The Environment
DDT Insecticide Persistent: stored in fatty tissues Bioaccumulation: builds up in an organism Biological magnification: increases as it passes up the food chain
Toxicant Mobility
Who got the biggest dose of DDT? Banned in U.S. in 1972
Toxicant Mobility
Chemicals move throughout environment
Biomagnification
Persistent Organic Pollutants
POP’s 12 very toxic chemicals Persistent, bioaccumulate, mobile
Persistent Organic Pollutants
Stockholm Convention (2001) Countries must eliminate production and use of POPs Except where no affordable alternative exists
Determining Health Effects Of Pollutants
Dose: amount that enters the body Response: type & amount of damage Lethal dose – mg/kg body wt.
Determining Toxicity
Lethal dose-50 percent LD50 Dose (mg/kg body wt) that is lethal to 50% of the population Determined for all new synthetic chemicals Animal testing
Lethal dose-50 percent
Determining Toxicity
Effective dose-50 percent ED50 Dose that causes 50% of population to exhibit specific response Animal testing
Dose-Response Curve
Shows effect of different doses Start with high doses Work way down to threshold level Maximum dose with no measurable effect Below is considered safe For some toxicants, there is no safe dose
Dose-Response Curve
Children & Chemicals
Children more susceptible: why? Still developing Higher metabolism Smaller in size
Cancer-Causing Substances
Carcinogens Expose animals to large doses Realistic? Ethical? Assumes one can work backward Process filled with uncertainty Accidental exposure studies New methods being developed
Case Study: Endocrine Disrupters
Act like natural hormones PCBs, dioxins, mercury, etc. Lake Apopka, Florida 1980 chemical spill Alligator eggs have high mortality rate
Case Study: Endocrine Disrupters & Humans
Increasing rates of: Reproductive disorders Infertility Some Cancers Lack of human studies Testing for endocrine disruptors now required by EPA