The ban is contentious for DDT, which is still used in tropical countries for control of malaria. Worldwide sales of chlordane and heptachlor were halted only in 1997, and use of existing stocks can be anticipated for some time. For the decision makers to effectively eliminate OC pesticides and other POPs from the world's atmosphere, they must know the origins of the compounds. Presently, sources that contribute to observed global atmospheric distributions are not fully understood. One novel approach for investigating pesticide recycling from soil and water involves using enantiomers as tracers.
Enantiomers have the same physical and chemical properties.
By examining ERs, it is possible to differentiate new sources of OC pesticides from ghosts of the past. The technique provides a sensitive indicator of biological degradation and clues about the origins of pesticides found in the atmosphere. Work performed by ourselves and other investigators demonstrates the potential usefulness of this approach. New sources, old sources OC pesticides are still being applied or have been used in the recent past in many tropical and subtropical countries. The conclusion that less developed countries are solely responsible for global contamination is, however, overly simplistic.