Persistent lipophilic contaminants and other chemical residues in the Southern Hemisphere

Data on the levels of persistent lipophilic contaminants and other chemical s have been reviewed and the dominant persistent lipophilic contaminants in the Southern Hemisphere found to be the chlorohydrocarbons commonly descri bed as the DDTs, HCHs, and the PCBs. The distribution patterns suggest that long-range transport, probably by global distillation, occurred with these substances. Endosulfan residues appear significant in areas of usage but t he data are limited. The data are in accord with a reduction in usage of ch lorohydrocarbons in developed countries, but an increase in usage in many t ropical countries. A systematic comparison of data on the northern and sout hern hemispheres indicates that the northern hemisphere is generally more c ontaminated than the southern hemisphere. It also suggests that the process of equilibration between the two hemispheres is relatively slow. In additi on, with the HCBs there is an equatorial to polar gradation in concentratio n probably as a result of global distillation. With the HCHs relatively hig h concentrations exist in the tropics, probably due to their heavy usage in these regions. With the HCBs, DDTs, and PCBs the concentrations appear to be more localized in relation to the sources because these substances are l ess volatile than the compounds mentioned previously.