Biological Effects of Low Level Exposures in Humans. R. R. Cook, Dow Corning Corporation, CO1120, Midland, MI 48686-0994
Epidemiology is an observational science that helps determine whether exposure to "toxic" agents result in meaningful perturbations in human health. It most often has been used to explore relative risks in the order of 2 to 5. Nonetheless, it offers some tantalizing evidence that low level exposures to both natural and so-called "man-made chemicals" may be associated with relative risks below one, i.e., with protective or paradoxical effects. This appears to be the case for a variety of agents ranging from vitamins, metals and pharmaceuticals to manufactured chemicals, including one of the most toxic: 2,3,7,8 tetrachlorodibenzo-p-dioxin.