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Polychlorinated biphenyl sources, environmental levels, and exposures in school buildings
Thomas, K., J. Xue, R. Williams, P. Jones, AND D. Whitaker. Polychlorinated biphenyl sources, environmental levels, and exposures in school buildings. ISES 2015 Annual Meeting, Henderson, NV, October 18 - 22, 2015.
The National Exposure Research Laboratory (NERL) Human Exposure and Atmospheric Sciences Division (HEASD) conducts research in support of EPA mission to protect human health and the environment. HEASD research program supports Goal 1 (Clean Air) and Goal 4 (Healthy People) of EPA strategic plan. More specifically, our division conducts research to characterize the movement of pollutants from the source to contact with humans. Our multidisciplinary research program produces Methods, Measurements, and Models to identify relationships between and characterize processes that link source emissions, environmental concentrations, human exposures, and target-tissue dose. The impact of these tools is improved regulatory programs and policies for EPA.
Background: Building materials and components containing polychlorinated biphenyls (PCBs) were used in some U.S. school buildings until the late 1970s and may be present today. There is limited information on source factors and occupant exposures. Methods: Analysis of PCBs in material samples from several schools provided information for characterizing sources and assessing source-environment relationships. PCB measurements in environmental media at six schools were used to estimate potential school-only exposure distributions for 4-5, 6-10, 11-14, and 14-18 year-old age groups using the Stochastic Human Exposure and Dose Simulation (SHEDS) multimedia model. Results: Using chamber-derived emission parameters, total PCB emission rates for caulks with >50,000 ppm PCBs in several school locations were estimated to range from 53 to 3100 µg/h. Total PCB emission rates estimated for four intact light ballasts tested in a chamber at 45°C ranged from 0.42 to 33 µg/h. Over 90% of 411 building material samples from schools with caulk and light ballast PCB sources had measurable PCBs (median=16 ppm total PCBs) showing secondary source creation. Geometric mean total PCB concentrations for air, surface wipes, and soil were 230 ng/m3, 0.15 µg/100 cm2, and 0.52 ppm respectively. Indoor dust concentrations estimated using an air/solid partition coefficient had a geometric mean of 7.0 ppm. For 6-10 year-olds, the estimated absorbed doses would be predicted to be 0.022 and 0.041 µg/kg-day at the 50th and 95th percentiles, respectively. Estimated absorbed doses were lower for the other age groups. Over 70% of the estimated mean absorbed dose was predicted to occur through inhalation. Conclusion: Occupants in schools with PCB sources are likely to be exposed to PCBs through their normal daily activities. Based on the levels in these buildings, some exposures occurring at school would be predicted to exceed the 0.02 µg/kg-day EPA IRIS reference dose for Aroclor 1254.