Lec38_39_Pesticides_05D

Lec38_39_Pesticides_05D - Pesticides Human Health the...

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Pesticides, Human Health, & the Environment V Students should... Gain an understanding of how & why pesticides are used in human society Develop perspective on the complex issues surrounding pesticides Learn to weigh risks of pesticide use, both pro and con V Pesticides Through Time 1200 BC Armies salt and ash fields 900 AD Chinese use arsenic 1690 Tobacco extracts used as insecticide 1800s Soaps & oils as insecticides 1939 DDT discovered by Paul Muller 1946 DDT resistance in houseflies 1962 “Silent Spring” by Rachel Carson 1970 Environmental Protection Agency 1973 Endangered Species Act H
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Pesticides in the “Good Old Days” circa 1900-1920 BOTTOM LINE: Today’s pesticide are much safer and less harmful that those in the “Good Old Days” H Inorganics Stable & water-soluble Stomach poisons Sulfur- fungicide used today arsenic boric acid- used today for cockroaches lead arsenate First insecticidal compounds Product for example only- does not constitute an endorsement by Virginia Tech V Organochlorines Nerve poison aldrin, dieldrin, toxaphene (soil insecticides) DDT Paul Muller won the Nobel Prize for discovering DDT Most beneficial use was in public health mosquitoes (malaria & yellow fever) lice (typhus) fleas (plague) Used during WWII and adapted for agricultural use. Cheap! Fat soluble & bio-accumulates Persistent (DDT half life is 10 years) H
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Organophosphates By-product of nerve gas research in WWII in Germany Used to replace persistent organochlorines Examples: Malathion: human louse control, flea powder Dichlorvos: pet collars & insect strips Non-persistent Many are systemic Product for example only- does not constitute an endorsement by Virginia Tech V Carbamates Nerve poisons: Inhibit cholinesterase Broad spectrum (low specificity) Short to medium persistence Relatively nontoxic to mammals Several systemic insecticides Examples: Dursban, for termite control Sevin, for home gardens Product for example only- does not constitute an endorsement
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