Background

Although use of DDT has been banned in some countries, it is still in use in many parts of the world and all wildlife and humans are exposed, with some exposures in the high ppm range.A world-wide ban of this pesticide is currently being considered, but this has become very controversial because DDT is used to control vectors of malaria, a disease which accounts for many deaths. Although agricultural usages of DDT is declining and will eventually end, human exposure from DDT use continues. Hence, it is now more important than ever to determine the potential effects of continued usage of this pesticide on humans. In addition, high concentrations of DDT and its metabolites, especially p,p'-DDE, persist in North American fields, farms, orchards, and Superfund sites. As a result, some wildlife populations still display incredibly high total DDT residues [i.e., 16,132,133]. Over the decades of use, some orchards may have had more than 1000 kg DDT applied per hectare [132], while around Lake Apopka it was reported that DDT was sometimes applied on a daily basis [133]. In the orchards and fields sampled by Elliott et al. [132], both migratory and nonmigratory birds had high tissue levels of p,p'-DDE (up to 103 mg/kg), while at Lake Apopka fat samples in birds were orders of magnitude higher. Elliott et al. [132] concluded that levels of 100 ppm in passerines were sufficiently high to present a considerable toxic hazard to birds of prey.

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