Monday, April 25, 2011

   
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ENDOSULPHAN




     Endosulfan is an off-patent organochlorine insecticide and acaricide. This colourless solid has emerged as a highly controversial agrichemical due to its acute toxicity, potential for bioaccumulation, and role as an endocrine disruptor. Banned in more than 63 countries, including the European Union, Australia and New Zealand, and other Asian and West African nations, and being phased out in the United States, Brazil and Canada. It is still used extensively in many other countries including India and China. It is produced by Bayer CropScience, Makhteshim Agan, and Government-of-India–owned Hindustan Insecticides Limited among others. Because of its threats to the environment, a global ban on the use and manufacture of endosulfan is being considered under the Stockholm Convention.

Uses

Endosulfan has been used in agriculture around the world to control insect pests including whiteflys, aphids, leafhoppers, Colorado potato beetles and cabbage worms. Because of its unique mode of action, it is useful in resistance management; however, because it is non-specific, it can negatively impact populations of beneficial insects. It is, however, considered to be moderately toxic to honey bees,and it is less toxic to bees than organophosphate insecticides.

Production

The World Health Organization estimated world wide annual production to be about 9,000 metric tonnes  in the early 1980s. From 1980–89, worldwide consumption averaged 10,500 t per year, and for the 1990s use increased to 12,800 t per year.
Endosulfan is a derivative of hexachlorocyclopentadiene and is chemically similar to aldrin, chlordane, and heptachlor. Specifically, it is produced by the Diels-Alder reaction of hexachlorocyclopentadiene with cis-butene-1,4-diol and subsequent reaction of the adduct with thionyl chloride. Technical endosulfan is a 7:3 mixture of stereoisomers, designated α and β. α- and β-endosulfan are conformational isomers arising from the pyramidal stereochemistry of sulfur. α-Endosulfan is the more thermodynamically stable of the two, thus β-endosulfan irreversibly converts to the α form, although the conversion is slow

Health effects

The Food and Agriculture Organization of United Nations has concluded that long-term intake of residues of endosulfan from uses that have been considered by the JMPR is unlikely to present a public health concern.[ Endosulfan is one of the most toxic pesticides on the market today, responsible for many fatal pesticide poisoning incidents around the world.Endosulfan is also a xenoestrogen—a synthetic substance that imitates or enhances the effect of estrogens—and it can act as an endocrine disruptor, causing reproductive and developmental damage in both animals and humans. Whether endosulfan can cause cancer is debated.

 Toxicity

Endosulfan is acutely neurotoxic to both insects and mammals, including humans. The US EPA classifies it as Category I: "Highly Acutely Toxic" based on a LD50 value of 30 mg/kg for female rats, while the World Health Organization classifies it as Class II "Moderately Hazardous" based on a rat LD50 of 80 mg/kg. It is a GABA-gated chloride channel antagonist, and a Ca2+, Mg2+ ATPase inhibitor. Both of these enzymes are involved in the transfer of nerve impulses. Symptoms of acute poisoning include hyperactivity, tremors, convulsions, lack of coordination, staggering, difficulty breathing, nausea and vomiting, diarrhea, and in severe cases, unconsciousness. Doses as low as 35 mg/kg have been documented to cause death in humans,and many cases of sub-lethal poisoning have resulted in permanent brain damage. Farm workers with chronic endosulfan exposure are at risk of rashes and skin irritation.
EPA's acute reference dose for dietary exposure to endosulfan is 0.015 mg/kg for adults and 0.0015 mg/kg for children. For chronic dietary expsoure, the EPA references doses are 0.006 mg/(kg·day) and 0.0006 mg/(kg·day) for adults and children, respectively..