Organochlorine pesticides (OCPs): dichlorodiphenyl trichloroethane (DDT), hexachlorocyclohexane (HCH), Hexachloran , aldrin , and THAN - have high toxicity, slow metabolism in natural objects, and bioaccumulation property. They are precursors of dioxins and dioxin-like substances. In assessing and predicting the danger of OCPs, their persistence (stability) in the environment, cumulative properties and long-term consequences are decisive. Due to the very slow destruction, pesticides accumulate in the environment and are transported over long distances by air, water and organisms. Fat-soluble OCPs accumulate in the food chain .