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AP Environmental Science Lesson 17-4 Report
Transcript of AP Environmental Science Lesson 17-4 Report
and deal with chemical hazards? Factors that determine harmful health effects: * Toxicology is the study of the harmful effects of chemicals, & toxicity is how harmful a substance is. Case Study: Protecting
Children from Toxic Chemicals: * 287 different chemicals that cause cancer, brain damage, birth defects or abnormal development were found in the blood off umbilical cords of babies Scientist's Tests to Estimate Toxicity: * the most widely used method of determining toxicity is to expose test animals to the chemical * Any synthetic or natural chemical can be harmful if ingested in a large enough quantity. This refers to dose - the amount of a chemical that a person takes in. * The effects also depend on a person's age, genetics & how effective his detoxification systems are, as well as the chemical's solubility, persistence & biological magnification. * The damage resulting from exposure to a chemical is called response. the response can be acute or chronic. * Babies & children are more susceptible to toxins because
1) they take in more (eating, drinking, and breathing)
2) they are exposed to more via putting things in their mouths
3) immune systems and detox processes do not work as well * The EPA says children are at 10 times higher risk than
adults; other scientists say 100 times is a safer
assumption. * They plot a dose-response curve to show their results based on how many die within a certain period of time for each dose. * threshold vs. non threshold & linear vs. nonlinear dose-responce models * More humane, but less accurate methods include
simulations, tissue culture/cell/robot device testing. nonthreshold
& linear threshhold & nonlinear * Some say this method is invalid because our bodies differ from those of animals, but others disagree. * the problems with all of these methods are that each human is exposed to different chemicals that change the effects of ones
they are testing inn a variety of ways. * scientists also refer to physicians care reports
and epidemiological studies for information. What Else we Know
About Harmful Chemicals: * Trace levels of chemicals have built up in almost
everyone's bodies from medicines and pollution, but there is
too little data to know if these levels are harmful. Based on the increasing life expectancy, most scientists consider this minor, * Some natural chemicals are more deadly than any synthetic ones. * Because of lack of knowledge, regulators set exposure limits well
below estimated safely levels. * "Toxicilogists know a great deal about a few chemicals, a little about many, and next to nothing about most", according to Joseph V. Rodricks. * 99.5% of commercially used chemicals are unregulated
due to insufficient evidence of their
harmful effects. Pollution Prevention &
the Precautionary Principle: * Scientists in european union countries are pushing
pollution prevention, but this means either (1) finding substitutes
for these chemicals or (2) recycling them like 3M companies & DuPont. * Pollution prevention is one strategy of the precautionary principle. * That is the idea that with reasonable evidence of a chemicals harmful effects, action should be taken without waiting for conclusive evidence. * Applying this principle strictly would mean new chemicals would have to be tested before used, and many chemicals being used would be banned. * this includes the "dirty dozen": 12 persistant organic pollutants (POPs)
such as DDT, PCB, Dioxins, Furans, and certain pesticides. * manufacturers and businesses argue that this would be too
expensive and make it almost impossible to any new chemical
or technology, and we can never be a risk free
society anyway. by Ashley Kochenour