Persistent lipophilic contaminants and other chemical residues in the Southern Hemisphere

Data on the levels of persistent lipophilic contaminants and other chemicals have been reviewed and the dominant persistent lipophilic contaminants in the Southern Hemisphere found to be the chlorohydrocarbons commonly described 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 the data are limited. The data are in accord with a reduction in usage of chlorohydrocarbons in developed countries, but an increase in usage in many tropical countries. A systematic comparison of data on the northern and southern hemispheres indicates that the northern hemisphere is generally more contaminated than the southern hemisphere. It also suggests that the process of equilibration between the two hemispheres is relatively slow. In addition, with the HCBs there is an equatorial to polar gradation in concentration probably as a result of global distillation. With the HCHs relatively high 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 less volatile than the compounds mentioned previously.