Chlorinated hydrocarbon insecticides: root uptake versus vapor contamination of soybean foliage.

The major environmental source of DDT (dichlorodiphenyltrichlo-roethane) residues in soybean plants arises from vapor movement from contaminated soil surfaces. In contrast, the presence of dieldrin, endrin, and heptachlor results primarily from root uptake and translocation through stems to leaves and seeds.