Pesticide Profile - Endosulfan

Quick Facts:

• Chemical name: 6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-
  2,4,3-benzadioxathiepin 3-oxide

• Trade names: Fan, Thiodan, Afidanil, Cekulfan, Endocel, Endodhan, Endosol, Endostar, Thionex, Cyclodan, Thimul, Thionex, Phaser, Thiodan, Devisulfan, Insectophene, Hoe 2671, Malix

• Pesticide Type: insecticide, acaricide

• Class: organochlorine (chlorinated hydrocarbon)

• Use: cotton, apples, pecans, various row vegetables, grapes, pears, peaches

•  Endosulfan is mutagenic in studies on yeast and bacteria.

• Endosulfan is a suspected endocrine disrupter.

• Endosulfan belongs to the same class of pesticides as DDT; it is highly persistent in the environment and has a high potential for bioaccumulation and biomagnification

• Very little is known about the toxicity and fate of endosulfan degradates.

Chemical Structure

Background

Endosulfan belongs to the class of pesticides known as organochlorines. These compounds are characterized by their high level of persistence in the environment, and their ability to bioaccumulate in animal tissue. Organochlorines, also known as chlorinated hydrocarbons, are insoluble in water and are usually highly soluble in fat. The chemicals absorb and remain in the fat cells of exposed animals. Effects of the organochlorines are sometimes greatest at the highest levels of the food chain, when large numbers of contaminated prey are consumed by top-level predators. This process, biomagnification, is what occurred when DDT, another organochlorine, was used extensively in the U.S. in the early 1970's. Peregrine falcons and bald eagles consumed fish exposed to DDT and accumulated toxic levels of the pesticide, resulting in reproductive failure.

Endosulfan is a Persistent Organic Pollutant (POP). It persists in the environment for extended periods of time, increasing the exposure risk of many non-target animals. It has been detected in wells and surface waters, most likely due to run-off or drift during application. It volatilizes easily after application and is transported to areas distant from the application site. It has been detected in ice and snow samples of the arctic.

Environmental Effects

Fate

• Persistence: endosulfan is moderately persistent in soils with an average half-life of 50 days. However, under certain conditions, endosulfan can be very long-lived in soils. The EPA has reported a half-life of 200 days but did not state the conditions under which the data were derived. In water, endosulfan has a high potential for contamination of waterways near the site of application. It is one of the most commonly detected pesticides in U.S. water. A study in 1982 found 24 of 154 wells in Ohio contaminated with endosulfan. Endosulfan is extremely persistent in aquatic systems under acidic conditions. Endosulfan has been detected in arctic ice and snow samples, attesting to its high degree of persistence. Published studies examining the toxicity and fate of endosulfan break down products are not available.

• Solubility: endosulfan is insoluble in water but is soluble in toluene and hexane.

• Soil mobility: Endosulfan is moderately mobile in soils, and will adhere to soil particles to a degree that contamination of surface waters due to runoff is a serious risk.

• Bioaccumulation: Endosulfan has a high potential for bioaccumulation. In studies that examined bioconcentration in fish, the bioconcentration factor was 11,538X. Residues of endosulfan have been detected in mussels, oysters and fish, in the field.

Ecotoxicity 

• Endosulfan is very highly toxic to aquatic fauna. Both vertebrate (fish, amphibians), and invertebrates (mollusks, insects, gastropods) are susceptible with LC 50's in the range of 1 ppb for many species.

• Endosulfan is highly toxic to mammals. The LD 50 for a rat is 18 mg/kg, for a cat, the LD 50 is 2 mg/kg. It is toxic through oral and dermal routes of exposure.

• Endosulfan is highly toxic to birds. The LD 50 for mallards is 12 mg/kg. Studies examining the chronic effects of endosulfan and its degradates are incomplete. Given the persistence of endosulfan in the environment and its potential for bioaccumulation, it is reasonable to expect chronic effects to birds at sub-lethal doses.