Canadian House Dust Study: population-based concentrations, loads and loading rates of arsenic, cadmium, chromium, copper, nickel, lead, and zinc inside urban homes.

The Canadian House Dust Study was designed to obtain nationally representative urban house dust metal concentrations (μg g(-1)) and metal loadings (μg m(-2)) for arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn). Consistent sampling of active dust of known age and provenance (area sampled) also permitted the calculation of indoor loading rates (mg m(-2) day(-1) for dust and μg m(-2) day(-1) for metals) for the winter season (from 2007 to 2010) when houses are most tightly sealed. Geomean/median indoor dust loading rates in homes located more than 2 km away from industry of any kind (9.6/9.1 mg m(-2) day(-1); n=580) were significantly lower (p<.001) than geomean (median) dust loading rates in homes located within 2 km of industry (13.5/13.4 mg m(-2) day(-1); n=421). Proximity to industry was characterized by higher indoor metal loading rates (p<.003), but no difference in dust metal concentrations (.29≥p≤.97). Comparisons of non-smokers' and smokers' homes in non-industrial zones showed higher metal loading rates (.005≥p≤.038) in smokers' homes, but no difference in dust metal concentrations (.15≥p≤.97). Relationships between house age and dust metal concentrations were significant for Pb, Cd and Zn (p<.001) but not for the other four metals (.14≥p≤.87). All seven metals, however, displayed a significant increase in metal loading rates with house age (p<.001) due to the influence of higher dust loading rates in older homes (p<.001). Relationships between three measures of metals in house dust - concentration, load, and loading rate - in the context of house age, smoking behavior and urban setting consistently show that concentration data is a useful indicator of the presence of metal sources in the home, whereas dust mass is the overriding influence on metal loadings and loading rates.