Human exposure to polychlorinated biphenyls (PCBs): a critical assessment of the evidence for adverse health effects.

Results from epidemiologic studies involving human exposures to polychlorinated biphenyls (PCBs) are often used to estimate the potential risk or hazard posed by the presence of these chemicals in the workplace or the environment. The use of results and conclusions from individual studies requires an assessment of the scientific quality of the information contained in published reports. The results of a critical review of the scientific literature reported here should be an aid to those who are interested in risk evaluations surrounding exposures to PCBs. There are diverse approaches that one could take to an evaluation of scientific reports of the health hazards of various chemicals. We present one approach to assessing the strengths and weaknesses of studies conducted to understand the potential association between PCB exposure and human health effects. A comprehensive review of the scientific literature involving human exposures to PCBs was performed and each study was evaluated on the basis of a defined set of criteria that were considered standards in epidemiologic research. Two of the 39 occupational studies reviewed provided positive evidence and 3 suggestive evidence for an exposure-related effect, whereas none of the 33 studies where exposure had occurred in the natural environment provided positive or suggestive evidence of an association with adverse effects.