Sorption of PCB from air to settled house dust in a contaminated indoor environment

Investigation of human exposure pathways to PCB in a high-rise estate in Denmark motivated an experiment with sorption of PCB from air to settled house dust. Three sieved house dust samples (<75 μm) of different origin were exposed to elevated air concentrations of PCB in a vacated apartment from seven to 40 days. Within the 40 days, most of the dust samples were close to equilibrium for the congeners PCB-8 to -101 and dust-air partition coefficients were determined. The dust samples of different origin showed comparable partitioning, though small differences were seen. The determined partition coefficients were in agreement with values found in literature. Further, the partition coefficients were compared to three sets of predicted estimates based on absorption of PCB into the organic matter of the dust and octanol-air partition coefficients derived from different sources. Comparing measured and predicted values (log-log), two sets of predicted values showed strong correlation, though overestimated 20-40%, while one set showed similar absolute levels, but with a few deviating congeners. Dust-air ratios were calculated for samples taken from a field investigation in homes with elevated air concentrations of PCB in the high-rises. The partitioning in the field samples were in agreement with the results from the exposure experiment and indicate near steady state conditions for the congeners in the dust from the homes. Dust exposed directly on the floorboards showed lower concentrations than samples placed on foil, indicating an ongoing sorption to the varnish being a tertiary source contaminated by the air.