Organochlorine pesticides have extremely strong bonds between their chlorine and carbon components and are attracted to fats and highly insoluble in water. The problem with their strength is that once organochlorine pesticides are used they can be around for a long time, in a human or animal body, in the water supply or in the soil.
The widest application for organochlorine pesticides is as an insecticide. When used, organochlorine pesticides can leech into our environment via direct application, contaminated waste disposal, incinerator emissions or runoff. These pesticides leech into human and animal bodies mainly via diet.
Since organochlorine pesticides don't breakdown easily in fatty tissue organochlorine pesticides can build up in animals and humans and even be passed on in this manner. For example, studies show that when a human or bird or other fish eats a fish that is contaminated with an organochlorine pesticide, that pesticide is passed on to the eater. Organochlorine pesticides can be passed through both food and beverages, such as milk from cows.
The widely discussed DDT is an organochlorine pesticide. DDT is a seriously dangerous pesticide that was banned in 1972 however, DDT is so strong that it's still showing up in the bodies of people today, including people born long after the DDT ban went into affect.