PCB AND DIOXIN REENTRY CRITERIA FOR BUILDING SURFACES AND AIR

A number of fires involving polychlorinated biphenyl (PCB)-containing transformers and capacitors have occurred in the United States. PCB fi res generate by-products such as polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzodioxins (PCDDs) and, when the transformer is in a building, contaminate the interior. Considerable concern exist s over the potential human health effects associated with exposure by inhabitants to residual levels of PCBs, PCDFs and PCDDs. Office worker s, for example, may be exposed to these chlorinated compounds via inha lation of contaminated particulates and vapors, dermal contact with co ntaminated surfaces, and incidental ingestion of dusts. A wide range o f re-entry or cleanup levels have been developed for PCDDs and PCBs to protect workers who re-occupy a building following a PCB fire. Re-ent ry criteria have been used by property owners and regulatory agencies to determine whether the building is safe to re-occupy or to determine the extent of needed remediation. This paper presents a mass balance approach to deriving risk-based re-entry surface and air criteria for PCBs and PCDD/PCDFs. These criteria were based on a lifetime risk leve l of 10(-5), recent toxicological data on PCDDs and PCBs, and plausibl e exposure scenarios. Our analysis suggests that 125 ng/m2 2,3,7,8-TCD D TEQ for surfaces and 10 pg/m3 for air are acceptable. Based on Arocl or 1260, risk-based re-entry criteria for PCBs on surfaces and in air were 750 mug/m2 and 0.1 mug/m3, respectively. In comparison to most pr evious guidelines, these risk-based criteria are less stringent, but c an still be considered conservative. The surface criteria are 5 to up to 125 fold higher than previous guidelines. Air criteria range up to 5 times higher than criteria used at past PCB fire sites. Air concentr ations associated with these were modeled and were negligible. For PCB s in air, the NIOSH guideline of 1 mug/m3 is also appropriate for occu pational settings.