Polychlorinated biphenyls in domestic dust from Canada, New Zealand, United Kingdom and United States: implications for human exposure.

Ingestion of indoor dust has been highlighted as an important pathway of exposure to brominated flame retardants. Hence, polychlorinated biphenyls (PCBs) were determined in indoor dust from homes in Amarillo/Austin, TX, USA (n=20; median concentration=200 ng Sigma PCB g(-1)); Birmingham, UK (n=20; 48 ng Sigma PCB g(-1)); Toronto, Canada (n=10; 260 ng Sigma PCB g(-1)); and Wellington, New Zealand (n=20; 46 ng Sigma PCB g(-1)). Concentrations in Canadian and US samples were statistically indistinguishable, but exceeded significantly (p<0.05) those in both New Zealand and UK dust. Principal component analysis revealed that while UK samples were enriched comparatively in lower molecular weight congeners; samples from other countries contained proportionally more mid-to-high molecular weight congeners. Concentrations of PCBs determined in air from the same 10 Canadian homes showed concentrations (median=4.9 ng Sigma PCB m(-3)) higher than those reported previously for UK homes (1.8 ng Sigma PCB m(-3)). Interpretation of these data alongside that for dietary exposure from other studies suggest that indoor exposures (i.e. air and dust combined) may be a significant contributor to overall exposure for the majority of the population - ranging from 4.3% to 87% in adults and 1.6-73% in toddlers. While inhalation is the principal indoor pathway under a typical dust ingestion scenario, exposure via dust ingestion exceeds that from either inhalation or diet for a small proportion of North American toddlers.