Development and application of an inhalation bioaccessibility method (IBM) for lead in the PM10 size fraction of soil

Abstract

An approach for assessing the inhalation bioaccessibility of Pb in the PM10 size fraction is presented, using an in vitro simulated epithelial lung fluid to represent the extracellular environment of the lung. The developed inhalation bioaccessibility method (IBM) is applied to a range of urban surface soils and mining wastes obtained from Mitrovica, Kosovo, a site where impacts upon human health following exposure to Pb have been internationally publicised. All Pb determinations were undertaken by inductively coupled plasma mass spectrometry (ICP-MS). The pseudo-total concentration of Pb (microwave acid digestion using aqua-regia) varied between matrices: smelter (20,900–72,800 mg kg−1), topsoil (274–13,700 mg kg−1), and tailings (2990 mg kg−1–25,300 mg kg−1). The in vitro inhalation bioaccessibility was typically several orders of magnitude lower: smelter (7.0–965 mg kg−1), topsoil (9.8–1060 mg kg−1), and tailings (0.7 mg kg−1–49.2 mg kg−1). The % inhalation bioaccessibility ranged from 0.02 to 11.0%, with the higher inhalation bioaccessible Pb concentrations being observed for samples from the Bosniak Mahalla area of Mitrovica (an area proposed for the relocation of internally displaced peoples). The estimated inhalation dose (for adults) calculated from the PM10 pseudo-total Pb concentration ranged from 0.369 to 1.284 μg kg−1BW day−1 (smelter), 0.005–0.242 μg kg−1BW day−1 (topsoil), and 0.053–0.446 μg kg−1BW day−1 (tailings). When daily inhalation doses were calculated using the bioaccessible Pb concentration the modelled exposure doses were much lower: smelter (0.0001–0.0170 μg kg−1BW day−1), topsoil (0.0002–0.0187 μg kg−1BW day−1) and tailings (0.0001–0.0009 μg kg−1BW day−1). Modelled for the neutral pH conditions of the interstitial lung environment, the results indicate a low potential inhalation bioaccessibility for Pb in these samples. Given the already elevated environmental Pb burden experienced by the local population, where significant prolonged dust or particulate generating activities are taking place, or where the inhaled particles are phagocytized, then inhalation exposure has the potential to significantly add to the overall Pb burden. Such data are important for local policy makers to better enable them to assess risk, especially in areas where soils/dusts have elevated levels of contamination. Keywords: Inhalation bioaccessibility, Lead, Soils, Human health, PM10