Evaluation of Risk From Exposure to Low-Level PCBs in Soil

摘要

Polychlorinated biphenyls (PCBs) were manufactured and used extensively from the 1940s through the late 1970s as heat transfer fluids in transformers and capacitors. Although no longer manufactured, PCBs continue to be used in some older equipment. PCBs refer to any commercial or other kind of mixture of congeners as environmental mixtures in air, water, soil, vegetation or as residues in human and animal tissue. The presence of low-level PCBs found in humans, primarily in fat and in the liver indicates its ubiquitous presence in the environment. The health effects of PCBs have been studied by evaluating various commercial PCB mixtures (Aroclors). At sites that have historically used or become contaminated with PCBs due to spills or process activities, there is potential for PCBs to have migrated to surrounding areas via wind- or water-borne transport and may be present in sediment or soil at varying concentrations. PCB-contaminated soil poses potential health risk to people exposed to such soils. This paper presents an evaluation of human health risk based on simulation of several exposure scenarios in which PCBs are present in soil at levels generally considered acceptable clean-up levels by regulatory agencies. Differences in carcinogenic risk characterization based on PCB congeners toxicity equivalents (TEQ) in comparison with risk from total PCBs measured as Aroclors will be presented. The risk characterization resulting from exposure to PCBs in residential, industrial/commercial, landscape worker and recreational park use settings will be presented. The carcinogenic risk ranges associated with low-level PCBs in soil can provide useful information in identifying and understanding how differences in toxicological information and risk assessment methodology can affect site-specific risk and perception of risk.