Bioaccessible and quasi-total metals in soil and indoor dust

Abstract

Children are exposed to metals via the ingestion of household dust and soil, but contaminated household dust is much less documented than outdoor soil. In France, environmental home surveys are carried out to assess the exposure of young children to bioaccessible lead. In other countries, most surveys of metal in dust are based on “total digestion” using strong acid to extract all the metals present in dust samples. To compare metal contamination in household dust in France with data from other countries, a sequential extraction protocol was developed to assay metal concentrations in the bioaccessible fraction as well as in “quasi-total” digestion. Nine metals (As, Cd, Cr, Cu, Mn, Pb, Sb, Sr and V) were chosen for analysis on the basis of their mean contamination level and toxicity. Analyses were performed by inductively coupled plasma mass spectrometry (ICP/MS). The “total” digestion was validated for metals using NIST Standard Reference Materials ® SRM 2583 and SRM 2584 for Cr, As, Cd and Pb in dust samples and nine metals in certified reference material CRM SS2 for soil samples. The quasi-total digestion recovery for the SRM dusts and CRM soil samples was more than 72 % for all metals, with a relative standard deviation of less than 14 %, except for Cd. For the first time, the bioaccessible fraction of metals was evaluated in SRM 2583, SRM 2584 and CRM SS2. This new protocol was tested on dust samples (75) and soil samples (4) from 13 French homes, and results are expressed here for the first time in μg/m 2 . The metal bioaccessibility in dust is very variable, ranging from 0 to 100 %. The most bioaccessible metals are Cd, Cu, Mn, Pb and Sr, while As, Cr, Sb and V are the least. This combined determination of metal concentrations in the bioaccessible fraction and quasi-total digestion from dust wipes and soil samples appears to be an appropriate method for assessing human exposure to metals via dust and soil ingestion.