Endrin is an organochlorine compound with the chemical formula C12H8Cl6O that was first produced in 1950 by Shell and Velsicol Chemical Corporation. It was primarily used as an insecticide, as well as a rodenticide and piscicide. It is a colourless, odorless solid, although commercial samples are often off-white. Endrin was manufactured as an emulsifiable solution known commercially as Endrex. The compound became infamous as a persistent organic pollutant and for this reason it is banned in many countries.
In the environment endrin exists as either endrin aldehyde or endrin ketone and can be found mainly in bottom sediments of bodies of water. Exposure to endrin can occur by inhalation, ingestion of substances containing the compound, or skin contact. Upon entering the body, it can be stored in body fats and can act as a neurotoxin on the central nervous system, which can cause convulsions, seizures, or even death.
Although endrin is not currently classified as a mutagen, nor as a human carcinogen, it is still a toxic chemical in other ways with detrimental effects. Due to these toxic effects, the manufacturers cancelled all use of endrin in the United States by 1991. Food import concerns have been raised because some countries may have still been using endrin as a pesticide.
History
J. Hyman & Company first developed endrin in 1950. Shell International was licensed in the United States and in the Netherlands to produce it. Velsicol was the other producer in the Netherlands. Endrin was used globally until the early 1970s. Due to its toxicity, it was banned or severely restricted in many countries. In 1982, Shell discontinued its manufacturing.
In 1962, an estimated 2.3-4.5 million kilograms of endrin were sold by Shell in the USA. In 1970, Japan imported 72,000 kilograms of endrin. From 1963 until 1972, Bali used 171 to 10,700 kilograms of endrin annually for the production of rice paddies until endrin use was discontinued in 1972. Taiwan reported to show higher levels of organochlorine pesticides including endrin in soil samples of paddy fields, compared to other Asian countries such as Thailand and Vietnam. During the 1950s-1970s over two million kilograms of organochlorine pesticides were estimated of having been be released into the environment per year. Endrin was banned in the United States on October 10, 1984. Taiwan banned endrin's use as a pesticide in 1971 and regulated it as a toxic chemical in 1989.
In May 2004, the Stockholm Convention on Persistent Organic Pollutants came into effect and listed endrin as one of the 12 initial persistent organic pollutants (POPs) that have been causing adverse effects on humans and the environment. The convention requires the participating parties to take measures to eliminate or restrict the production of POPs.
Production
The synthesis of endrin begins with the condensation of hexachlorocyclopentadiene with vinyl chloride. The product is then dehydrochlorinated. Following reaction with cyclopentadiene, isodrin is formed. Epoxide formation by adding either peracetic acid or perbenzoic acid to the isodrin is the final step in synthesizing endrin.
Endrin is a stereoisomer of dieldrin with comparable properties, though endrin degrades more easily.
Use
Endrin was formulated as emulsifiable concentrates (ECs), wettable powders (WPs), granules, field strength dusts (FSDs), and pastes. The product could then be applied by aircraft or by handheld sprayers in its various formulations.
Endrin has been used primarily as an agricultural insecticide on tobacco, apple trees, cotton, sugar cane, rice, cereal, and grains. It is effective against a variety of species, including cotton bollworms, corn borers, cut worms and grass hoppers. In addition, endrin has been employed as a rodenticide and avicide. In Malaysia, fish farms used a solution of endrin as a piscicide to rid mine pools and fish ponds of all fish prior to restocking.
A study conducted from 1981 to 1983 in the US aimed to determine endrin's effects on non-target organisms when applied as a rodenticide in orchards. Most wildlife in and around the orchard was found to have endrin exposure, with endrin toxicity accounting for more than 24% of bird deaths recorded. Endrin was eventually banned in the US on October 10, 1984.
Health effects
Exposure and metabolism
Exposure to endrin can occur by inhalation, ingestion of substances containing the compound, or by skin contact. In addition to inhalation and skin contact, infants can be exposed by ingesting the breast milk of an exposed woman. In utero, fetuses are exposed by way of the placenta if the mother has been exposed.
