Indoor Dust Metal Loadings: A Human Health Risk Assessment

In order to characterize the influence of environmental factors in dust metal loadings inside homes in an urban environment and to evaluate the associated potential health risks, samples of settled indoor dust from 10 apartments in the urban area of Madrid (Spain) were collected with wet wipes. Cd, Cr, Cu, Pb, Zn, Ni, and Mn loads were determined by Atomic Absorption Spectroscopy (AAS) after a HNO3 + H2O2 digestion. The environmental factors evaluated were load distribution between rooms, number of residents, presence of smokers, traffic intensity, apartment elevation, and frequency of house cleaning. Tukey's range test and stepwise multiple linear regression analysis revealed that metal dust loadings present two prevailing origins: (1) They present higher loadings in the entry hall, which suggest that dust is tracked indoors adhered to footwear and clothing and (2) they arise from tobacco smoking. Significant correlations were also observed between metal loadings and traffic intensity (Cr), number of residents (Cr, Pb, and Cu), number of days between cleaning (Ni), and flat height (Mn). A human health risk assessment considering a mechanistic hand-to-mouth model for dust ingestion and dermal absorption revealed that urban children are not expected to develop adverse health effects from exposure to trace elements in household dust. The contribution of this exposure scenario to the overall received dose should be included when assessing the background exposure of children to trace elements. A more precise assessment should attempt to reduce the significant uncertainty of the risk model output associated with estimates of exposure variables, deposition rates, and metal bioaccessibility.