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Abstract

Growing public concern about the past use of polychlorinated biphenyl (PCB) containing building caulk in schools has prompted expensive caulk removal projects at a time of limited public resources. Building caulk, used during construction to fill narrow gaps around windows and door frames, was often formulated with PCBs to increase its plasticity and durability. This PCB use was banned in 1978, but even three or more decades later, schools with PCB containing caulk may still have detectable levels of PCBs in indoor air. The USEPA has expressed concern that the inhalation of these airborne PCBs may be a significant exposure pathway for children. Despite their presence in buildings for more than 30 years, there have been no reported adverse health effects attributable to PCBs in building caulk or other building materials. Health concerns about PCBs in schools are based on results of risk assessment models that rely on toxicity factors derived from animal studies. The USEPA has opted to use animal studies for estimating PCB risk to people even though there is abundant evidence that PCBs are significantly less toxic to people than they are to animal test species. PCB numerical risk modeling for schools appears to be an instance where there has been a significant overestimation of the actual risk posed to children. There is a considerable body of human health data derived from occupational and non-occupational settings that supports the view that human PCB toxicity is not accurately represented by the USEPA toxicity factors, particularly the cancer slope factors. This article explores human PCB toxicity by reviewing three lines of scientific evidence: 1) a closer look at the actual causes of the Yusho and Yu-Cheng rice oil poisonings; 2) a comparison of the human health effects from PCBs to those caused by three other common environmental contaminants; and 3) a brief review of the arguments used to support the claim of PCB carcinogenicity. If PCBs are significantly less toxic than represented by the USEPA cancer slope factor, then expensive efforts to remove building caulk and other PCB containing materials from schools may provide no health benefit. At a time of contracting school system budgets, avoiding unnecessary expenses is an obvious priority.

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