Integrated Risk Information System (IRIS) Assessment of PCBs: Supporting Data
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Polychlorinated biphenyls (PCBs) were produced commercially in the United States from 1929-1977 for use in a wide variety of applications. Unfortunately, the unique chemical properties of PCBs that made them so useful (e.g., thermal stability, resistance to acids and bases, low water solubility) also contributed to their resistance to degradation, bioaccumulation in food chains, and toxicity. Although the commercial manufacture of PCBs was banned in the United States in 1979, even today, PCBs are ubiquitous in human blood, adipose tissue, and breast milk. PCBs can be found in marine and fresh water fish, and fish consumption constitutes a major source of human exposure to these chemicals. Inhalation has also been shown to be a contributor to total PCB exposure, especially in indoor settings where PCB sources exist. General population exposure may also occur via dermal contact with PCBs in soil or other media, or incidental ingestion of PCB-contaminated soil or dust. Currently, there are two Integrated Risk Information System (IRIS) reference doses (RfDs) available for use in assessing human health risk associated with PCB exposure, one for the commercial PCB mixture Aroclor 1016 established in 1993, and another for Aroclor 1254 established in 1994. PCB research since the time that these values were published has provided additional information to be considered in a new IRIS assessment currently under development to evaluate noncancer human health hazards associated with PCB exposure. This presentation will provide an overview of the hazard identification and dose-response strategies planned for the new assessment as well as a summary of the the types of research data considered to support assessment development.