GASTRIC AND INTESTINAL BIOACCESSIBILITY OF METALS FROM URBAN DUSTS AS A FUNCTION OF MINERALOGY AND GRAIN SIZE

Oral bioaccessibility of metals from urban dust was evaluated considering three grain size fractions: ≤0.044mm, 0.044-0.072mm, and ≥0.072mm. Metal concentration in bulk samples was determined and spatial distribution of Cu, Mn, Pb, Cd, As, and Zn was achieved. Gastric and intestinal bioaccessibility was obtained for the six metals and three grain fractions by PBET method. Mineral characterization was conducted by XRD and the metal soluble fraction linked to mineral group (carbonates, oxides, sulfides) was studied by sequential extraction chemical methods. Bulk metal content increases in smaller grain size (≤0.044mm); however, the bioaccessibility is not linked to grain size but it shows a geographic distribution possibly linked to pollution sources. Copper, cadmium, and zinc show greater bioaccessibility (gastric and intestinal) in the north of the city. Intestinal bioaccessibility of Pb is greater in the west, although the levels of total Pb (bulk) would be higher in the east. The sequential extraction indicates that Cu, Cd, and Pb are associated mostly to carbonates in areas of high vehicular traffic. The results of this work represent the first obtained BAF data for urban dust in México, thus impacting health risk assessment, and the use of GIS for spatial distribution of BAF is a powerful tool for future biomarker studies.