Chlorinated dioxins and dibenzofurans in the environment--a hazard to public health?

Polychlorinated dibenzodioxins (PCDD) and polychlorinated dibenzofurans (PCDF) are globally distributed, are persistent in the environment, and tend to accumulate in human tissues. Several 2,3,7,8-substituted PCDD and PCDF have been found at parts-per-trillion levels in human milk and adipose tissue. Food is the major source for the general population. Above-average exposures may be caused by the incineration of various wastes, certain industries (eg, metal and paper and pulp), and traffic exhaust. PCDD and PCDF have been of great public concern because one of the congeners, 2,3,7,8-tetrachlorodibenzodioxin, is an extremely potent carcinogen and teratogen in rodents. Although epidemiologic studies on cancer are too few for conclusions, animal studies and documented human exposure suggest that humans may be at increased risk. Human exposure is generally low when compared with the effective levels for rodents. However, part of the population can be more exposed and, consequently, also be potentially at higher risk.