The mobility and human oral bioaccessibility of Zn and Pb in urban dusts of Estarreja (N Portugal)

Twenty-one samples of urban dust were collected from Estarreja city (Portugal). The main objective of this work was to assess the potential availability of Pb and Zn present dust samples from Estarreja city via the oral ingestion exposure route using a combination of geochemical tests: (a) using sequential extraction to identify the fractionation of the Pb and Zn within the geochemical components that make up the dust and (b) in vitro bioaccessibility (BA) measurements to identify which components are the source(s) of the bioaccessible fraction (Bf). These samples were analysed for their quasi-total contents of Pb and Zn by inductively coupled plasma mass spectrometry, for their element solid-phase distribution using selective sequential extraction method and for the Bfs of these elements using a physiologically based extraction test. The study showed that the concentrations of Zn were higher than Pb, but both are site-specific. The sequential extraction test shows that the exchangeable and acid-soluble phases are important bearing phases for Pb and Zn. The BA test showed that a high proportion of the total concentration is available for absorption into the human body (ranges from 22.5 to 84.1 % for Pb and 28.7 to 86.3 % for Zn).