Endosulfan is an organochlorine compound that is used as an 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, several Asian and West African nations, and soon in the United States,it is still used extensively in many other countries including India and Brazil. 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. It has also seen use in wood preservation, home gardening, and tse-tse fly control, though it is not currently used for public health purposes. India is the world's largest consumer of endosulfan. 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 organophosphateinsecticides.
Production
The World Health Organization estimated world wide annual production to be about 9,000 metric tonnes (t) 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.
History of Endosulfan commerciallization and regulation
- Early 1950s Endosulfan developed.
- 1954 Hoechst AG (now Bayer CropScience) wins USDA's approval of endosulfan in the US.
- 2000 Home and garden uses are terminated by agreement with the EPA.
- 2002 The U.S. Fish and Wildlife Service recommends that endosulfan should be cancelled, and the EPA determines that endosulfan residues on food and in water pose unacceptable risks. The agency allows endosulfan to stay on the market, but imposes restrictions on its agricultural uses.
- 2007 The international community takes steps to restrict the use and trade of endosulfan. It is recommended for inclusion in the Rotterdam Convention on Prior Informed Consent,[15] and the European Union proposes to add it to the list of chemicals banned under the Stockholm Convention on Persistent Organic Pollutants. If approved, all use and manufacture of endosulfan would be banned globally.Meanwhile, Canada announces that endosulfan is under consideration for phase-out in that country, and Bayer CropScience voluntarily pulls its endosulfan products from the U.S. market but continues to sell them abroad.
- 2008 In February, environmental, consumer, and farm labor groups including the Natural Resources Defense Council, Organic Consumers Association, and the United Farm Workers call on the U.S. EPA to ban endosulfan. In May, coalitions of scientists, environmental groups, and arctic tribes ask the EPA to cancel endosulfan, and in July a coalition of environmental and workers groups file a lawsuit against the EPA challenging its 2002 decision to not ban it. In October, the Review Committee of the Stockholm Convention moved endosulfan along in the procedure for listing under the treaty, while India blocked its addition to the Rotterdam Convention.
- 2009 New Zealand bans endosulfan. The Stockholm Convention's Review Committee agrees that endosulfan is a persistent organic pollutant and that "global action is warranted", setting the stage of a global ban.
- 2010 U.S. EPA announces that all uses of endosulfan in the U.S. will be cancelled and that it is in negotiations with Makhteshim Agan of North America to phase the organochlorine out.Australia also banned the use of the chemical.
