Dichlorodiphenyltrichloroethane (DDT) was used in the Second World War. This played a vital role in controlling fleas, lice and other disease carriers. “It was subsequently used to kill mosquitoes, and helped control malaria”2. DDT is now banned in Britain because it accumulates along food chains. DDT is sprayed on green plants to control greenfly’s. Most of the greenfly die and some of the greenfly survive. The greenfly that survives gets eaten by birds (tits). The concentration of DDT accumulates in the bodies of the tits, and then the tits get eaten by the sparrow hawk. When the concentration of DDT is high enough the sparrow hawk dies.
“The sparrow hawk is one of the commoner birds of prey in the UK, but in the early 1960s numbers fell dramatically. In 1949 several hundred pairs bred in Norfolk. By 1965 a single breeding pair remained.” (From AS AQA biology text book)
Modern chemical pesticides are much less persistent, but they may be highly toxic to some non-target organisms. For example Phosphamidon, is a pesticide which was intended to be used to replace DDT in forest protection, which killed a large number of birds. When fenitrothion was sprayed in forests it replaced DDT and phosphamidon, this has less severe effects. This still remains a cause for environmental concern.
Pesticide are harmful to humans, direct contact to pesticide and inhalation can cause damage.
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Each year in the U.S., some 110,000 pesticide poisonings are reported by poison control centers, and 23,000 people visit emergency rooms for the same reason. And every year, about 20 people nationwide -- mostly children -- die from accidental pesticide poisoning. (from )
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Forty cases were in one accident, where workers were overcome by pesticide poisoning in a vegetable field. The field had been sprayed the evening before, with a product requiring a 24-hour re-entry period. This re-entry was violated and 40 employees were seriously affected. (from )
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Pesticides also poison livestock, fish and wildlife. They kill pollinators, such as birds, bees and butterflies; disrupt the balance of ecosystems; and reduce biological diversity. (from http://www.panna.org/resources/documents/WBfailureToCurb.dv.html)
Pesticide also effects the environment, the spread of hazardous pesticides throughout Earth's air, soil, water and food chain.
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Most environmental risks and ecological damage from pesticide use result from toxic effects of pesticides on various living organisms. Studies have found insecticides are the most toxic class of pesticides, followed by herbicides, acaricides (mite killers) and fungicides. (from )
Air currents can carry pesticides that were sprayed in a nearby area. This is known as pesticide drift.
Exposure to pesticides can lead to serious side effects, including:
- Redness, swelling, or blistering of the skin
- Stinging or swelling of the eyes, mouth, and nose
- Shortness of breath
- Nausea and vomiting
- Diarrhea
- Headache
- Fatigue
People can be affected by pesticide poisoning through food, air and water. If too much pesticide is added to the crops this is then washed off by rain. This water falls to the water bed then into a river or a lake, this can cause contamination because private well are not tested for contamination. Since food is made out of crops and other crop plants trace amounts of pesticide can be found.
“SMALL doses of pesticide are enough to hit frogs where it hurts them most -in the immune system. This might explain the mysterious disappearance of amphibians all around the globe.” (From New Scientist 04 May 2002)
“Pesticides are believed to break down under UV light to form poisons that trigger deformities in amphibians (New Scientist, 13 September 1997, p 18) , and weedkillers can turn male frogs into females.” This shows that pesticides effect the population of the frogs.
Bibliography
1) .
2) New Understanding Biology Book, for advanced level, forth edition, Glenn and Susan Toole.
3) .
4) http://www.panna.org/resources/documents/WBfailureToCurb.dv.html.
5) AS AQA biology text book Bill Inge, Martin Rowland, Margaret Baker.
6) New Scientist 04 May 2002.
7) New Scientist, 13 September 1997, p 18
