Endosulfan

Endosulfan is an organochlorine insecticide and acaricide, and acts as a contact poison in a wide variety of insects and mites. Endosulfan is effective against a wide range of insects and certain mites on cereals, coffee, cotton, fruit, oilseeds, potato, tea, vegetable and other crops(1). It can also be used as a wood preservative.

Endosulfan is sold as a mixture of two different forms of the same chemical (alpha- and beta-endosulfan). Its colour is cream to brown and it smells like turpentine(2).
    Endosulfan is a highly toxic substance. The World Health Organisation (WHO) classifies endosulfan in Category II (moderately hazardous). The US Environmental Protection Agency (US EPA) classifies it as a Category 1b (highly hazardous) pesticide(3). Short-term toxicity is high, and influenced by the solvents and emulsifiers used to dissolve it(4). Endosulfan is easily absorbed by the stomach, by the lungs and through the skin, meaning that all routes of exposure can pose a hazard(5). Exposure to endosulfan may result from, for example: breathing air near where it has been sprayed; drinking water contaminated with it; eating contaminated food; touching contaminated soil; smoking cigarettes made from tobacco with endosulfan residues; or working in an industry where endosulfan is used(6). Proper protective clothing (safety goggles, gloves, long sleeves, long pants, respirator) is needed to prevent poisoning when handling endosulfan(7).

Acute toxicity
Stimulation of the Central Nervous System is the main characteristic of endosulfan poisoning. Symptoms of acute exposure include hyperactivity, tremors, decreased respiration, salivation, anaemia(8), and also unco-ordination and a loss of ability to stand(9). Other signs of poisoning include gagging, vomiting, diarrhoea, agitation, convulsions and loss of consciousness. Blindness has been observed in cows, sheep and pigs which have grazed in fields sprayed with the compound(10). People with diets low in protein may be more sensitive to the effects of this pesticide(11). 

Chronic effects
Although the short-term toxicity of endosulfan is of immediate concern, there are also long-term effects to consider. Animal studies have shown effects on the kidneys, developing foetus, and liver from longer-term exposure to low levels of endosulfan. The ability of animals to fight infection was also lowered(12). Organochlorine compounds, including DDT, PCBs and endosulfan, may be part of the cause for the decrease in the quality of semen, in increase in testicular and prostate cancer, an increase in defects in male sex organs, and increased incidence of breast cancer which has been observed in the last 50 years. Endosulfan has also been found to cause mutations(13).

Environmental fate
As for the environmental effects of endosulfan use, the compound has adverse effects on aquatic systems, and is highly toxic to fish, birds, fowl, bees and wildlife(14). According to other sources(15,16) however, endosulfan is relatively non-toxic to beneficial insects such as parasitic wasps, ladybirds and some mites.
    Endosulfan has only a moderate potential for bioaccumulation(17). It breaks down much faster than the other organochlorines(18), and it leaves the body fairly quickly(19). Despite its rapid degradation in water, endosulfan can persist for a relatively long period when bound to soil particles, which can be a source of later contamination(20). The advantage is that there is no threat of leaching to groundwater, but the disadvantage is that endosulfan may be particularly prone to run-off immediately after spraying. 'Adequate management of soil and water on cotton farms is required to prevent transport off-farm to minimise this threat.' (21).
    The half-life of endosulfan in water and in most fruits and vegetables is reported to be three to seven days(22). However, half-life in sandy loam is reported to be between 60 and 800 days(23). The degradation rate is dependent on the pH of the soil: alkaline conditions favour degradation, whereas acidic conditions slow down the process(24,25). Adding endosulfan to soil appears to reduce the rate of degradation of other organochlorine pesticides already present in the soil, either because endosulfan reduces the populations of micro-organisms, or because of reduction of the activity of micro-organisms responsible for degradation of the other organochlorines(26).

Breakdown product
A big drawback with endosulfan is that the breakdown product, endosulfan sulphate, is more persistent than the parent compound, accounting for 90% of the residue in 11 weeks. Sulphate formation increases as temperatures increase(27). In Australia significant amounts of endosulfan sulphate were observed in soil prior to spraying as residue from applications in previous seasons(28).
    The regulatory status of endosulfan differs from one country to another, but a lot of countries have found it relevant to put in place specific regulation on endosulfan use, by banning, restricting, or severely restricting it. Endosulfan has been banned in at least the following countries: Denmark, Germany, Netherlands, Sweden(29), Belize and Singapore(30), and the Brazilian state of Rondonia(31). Colombia(32) and Indonesia(33) were preparing for a ban on endosulfan. Its use is not allowed either in rice fields in Bangladesh, Indonesia, Korea and Thailand. Use is restricted or severely restricted in: Canada, Finland, Great Britain, Kuwait, the Philippines, Russia, Sri Lanka and Thailand(34) and in Madagascar(35). Campaigns have been going on world-wide for several years to ban endosulfan completely(36,37).

References
1. Ghadiri, H., C.W. Rose and D.W. Connel, Controlled environment study of the degradation of endosulfan in soils. In G.A. Constable and N.W. Forrester (eds.), Challenging the future. Proceedings of the World Cotton Research Conference - 1, Brisbane, Australia, February 14-17, 1994, CSIRO, Melbourne, Australia, 1995, pp. 583-588.
2. ATSDR, Endosulfan datasheet. Agency for Toxic Substances and Disease Registry, Public Health Service, US Department for Health and Human Services, USA, September 1995, 3pp.
3. PANAP, Endosulfan datasheet. Pesticide Action Network - Asia and the Pacific, Penang, Malaysia. June 1996, 6pp.
4. EXTOXNET, Endosulfan datasheet. Extoxnet, Ithaca N.Y., USA. October 1992, 4pp.
5. PANAP 1996, op cit.
6. ATSDR, 1995, op cit.
7. PANAP, 1996, op cit.
8. ATSDR, 1995, op cit.
9. EXTOXNET, 1992, op cit.
10. EXTOXNET, 1992, op cit.
11.  ANAP, 1996, op cit
12. ATSDR, 1995, op cit.
13. PANAP, 1996, op cit.
14. PANAP, 1996, op cit.
15. EXTOXNET, 1992, op cit.
16. Kern, M.J. and Geiss, Investigations on the suitability of Thiodan (for IPM on cotton). Paper presented at the World Cotton Research Conference - 2, Athens, Greece, September 6-12, 1998, Hoechst Schering AgrEvo GmbH, Frankfurt, Germany.
17. PANAP, 1996, op cit.
18. Endosulfan is often compared favourably to organochlorines like DDT, aldrin and dieldrin, as it is less persistent in the environment. It should be noted that such a comparison is likely to seriously underestimate its absolute environmental effects.
19. ATSDR, 1995, op cit.
20. Ghadiri, 1995, op cit.
21. Kimber, S.W.L., S.K. Southan, N. Ahmad and I.R. Kennedy, The fate of endosulfan sprayed on cotton. In G.A. Constable and N.W. Forrester (eds.), Challenging the future. op cit pp. 589-594. 22. Ghadiri, 1995, op cit.
23. PANAP, 1996, op cit.
24. EXTOXNET, 1992, op cit.
25. Ghadiri, 1995, op cit.
26. Ghadiri, 1995, op cit.
27. EXTOXNET, 1992, op cit.
28. Kimber et al, 1995, op cit.
29. Muilerman, H., Society for Nature and Environment, The Netherlands, personal communication, 30 November 1999.
30. PANAP, 1996, op cit.
31. De Oliveira, J.N.A. and A. De Oliveira Toniato, The alarming use of agrochemicals in Rondonia, Brazil. PN 27, March 1995, pp. 4-7.
32. PAN-Africa, Bannir l'endosulfan en Colombie? In: Pesticides and Alternatives, No. 001, September 1996, pp. 11.
33. Indonesia bans OPs. PN 34, December 1996, p. 18.
34. PANAP, 1996, op cit.
35. Von Hildebrand, A., Pesticide problems and IPM: Implementation in Madagasca, PN 25, September 1994, pp. 12-13.
36. PAN-Africa 1996, op cit.
37. PANAP, 1996, op cit.

[This article first appeared in Pesticides News No.47, March 2000, p20]