Environmental risk assessments, fate and transport models, and sediment quality guidelines maybe on shaky foundations because some of the basic data needed to predict the fate of a contaminant have large errors, according to a detailed analysis by United States Geological Survey (USGS) physical chemists James Pontolillo and Robert Eganhouse (pubs.water. usgs.gov/wriol-4201/) (1). Other scientists say that the problem is nothing new and doesn't significantly affect models and policy decisions. The USGS report claims that there is an alarming level of uncertainty in reported octanol-water partition coefficients (K{sub}(OW)S) and aqueous solublilties (S{sub}Ws) for the notorious insecticide DDT and its primary metabolite, DDE. These variables are conventionally reported as their logarithms. In a detailed review of some 700 publications from 1944 to 2001, Pontolillo and Eganhouse found up to 4 orders of magnitude variation with no convergence over time. They conclude that the reliability of the entire DDT and DDE K{sub}(OW) and S{sub}W database is questionable and believe that the problems "are probably indicative of a more general problem in the literature of hydrophobic organic compounds." (1)
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