Organochlorine pesticides are chemically produced pesticides which include DDT, dieldrin, heptachlor, chlordane, endosulfan and dicofol. Many types where widely used as insecticides throughout the 1950's and 1960's until their use was banned in western countries since the 1970's. Many organochlorine pesticides are extremely persistent in the environment. They have a low solubility in water and therefore tend to adsorb on to particles. They tend to end up in the lipids of living organisms making them difficult to excrete and causing them to bioaccumulate. They also biomagnify, which causes the top predators of the food chain to contain high concentrations of these compounds. Originally they were used as pesticides in terrestrial ecosystems. However, they are flushed away from terrestrial ecosystems trough rivers and end up in marine ecosystems. Due to their low solubility and high adsorption to particles and lipids this takes years to decades. 
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