Chapter 7 Notes

Chapter 7 Notes - Sean O'Brien AP Environmental Science...

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Sean O’Brien AP Environmental Science Period 2 Mr. G. Cusimano 14 September 2009
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Chapter 7 – Human Health and Environmental Toxicology (pg. 148) Determining Health Effects of Environmental Pollution (pg. 157) The study of adverse health effects of agents in environment is known as “toxicology.” The effects of toxic agents can be immediate (acute toxicity) or prolonged (chronic toxicity). Acute toxicity : effects range from dizziness to death following a single exposure. Chronic toxicity : effects of damage to vital organs (liver, kidneys) following a long term, low-level exposure. Toxicity is measured by “dose” at which adverse effects are produced. A dose is the specific amount of agent that enters the organism. A response is the type and amount of damage caused by exposure to a particular dose. A dose may cause death (lethal) or harm without causing death (sub-lethal). Lethal doses are usually expressed in units of mg (milligrams) of agent per kg (kilogram). o = ppm mgkg Toxicity is usually determined by administering various doses of agents to populations of laboratory animals and measuring the responses observed. o These data are than used to predict human health effects. The dose that is lethal to 50% of the population is called the “lethal dose – 50%” or “LD 50 .” Acute toxicity and LD 50 are inversely related; that is the smaller the LD 50 the more toxic the agent. The LD 50 is determined for all new synthetic chemicals produced.
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o The assumption is also made that if an agent is toxic at low levels for several species, then it is also toxic to humans. For a wide range of biological responses, the “effective dose – 50%” or “ED 50 ” is used. o Examples: stunted development in the offspring of pregnant animal, reduced enzyme activity, onset or hair loss, and deformities. ED
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This note was uploaded on 09/20/2009 for the course BUS 306 taught by Professor Selvili during the Spring '08 term at USC.

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Chapter 7 Notes - Sean O'Brien AP Environmental Science...

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