In the past, a major source has undoubtedly been agriculture, because compounds such as DDT, dieldrin, aldrin, endrin and heptachlor were widely used as pesticides. ###>Dans le passé, une importante source a sans aucun doute été l'agriculture, qui utilisait comme pesticides de grandes quantités de composés tels que le DDT, la dieldrine, l'aldrine, l'endrine et l'heptachlore.