Toxic Contaminants in the Environment: Persistent Organochlorines

Technical Supplement: Global context of DDT and PCBs (Additional Info)

DDT has been banned by most western industrial nations, but it is still widely used in developing countries. In 1985, the amount of DDT in world use was estimated to be about the same as before western countries banned its general use in the early 1970s.

For developing nations, DDT is relatively inexpensive and easy to produce domestically. Its effectiveness against crop pests and insects carrying diseases such as malaria and typhus has helped to save millions of lives.

Recent surveys of DDT in marine environments around the globe (Iwata et al. 1993) found that concentrations in air and water were higher in the northern hemisphere than in the southern hemisphere. Concentrations were highest near tropical Asia.

The distributions of PCB concentrations in both air and water were relatively uniform in both hemispheres, including polar regions. This suggests that the atmosphere is a particularly important medium for the transport of PCBs and raises concerns about the contamination of vulnerable Arctic ecosystems (Iwata et al. 1993).

Total world production of PCBs to 1988 has been estimated to be 1.2 million tonnes. Of this, 31% is thought to be already in the environment, 4% has been destroyed, and 65% is still in use or in storage. Thus, more than twice the amount now in the environment is still available for possible future contamination (Tanabe 1988).

Iwata, H.,S. Tanabe, N. Sakai, and R. Tatsukawa. 1993. Distribution of persistent organochlorines in the oceanic air and surface seawater and the role of ocean on their global transport and fate. Environmental Science and Technology 27(6):1080–1098.

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