Lung bioaccessibility of metals in particulate matter from contaminated soils and mine tailings

Human exposure to particulate matter (PM) has been associated with adverse health effects. While inhalation exposure to airborne PM is a prominent research subject, exposure to PM of geological origin has received less... [ view full abstract ]

Human exposure to particulate matter (PM) has been associated with adverse health effects. While inhalation exposure to airborne PM is a prominent research subject, exposure to PM of geological origin has received less attention. Inhalation of PM from contaminated soils or mine tailings into residential environments may impact both indoor and outdoor exposures. Thus, exposure assessment warrants the use of in vitro bioaccessibility testing to predict lung bioavailability of metals. The present study aims to (1) characterize contaminated soils (n=6) and mine tailings samples (n=3) for As, Cu, Fe, Mn, Ni, Pb, and Zn content; and, (2) determine elemental lung bioaccessibility in PM20 by using Gamble’s solution (GS) and artificial lysosomal fluid (ALF). Metal concentrations were elevated in bulk samples, particularly for As (up to 2,040 mg.kg-1), Fe (up to 59.8%), Mn (up to 6,510 mg.kg-1), and Zn (up to 4,060 mg.kg-1) and metal concentrations in PM20 were almost always higher. In vitro tests using ALF predicted higher bioaccessibility than the ones using GS. Bioaccessibility in ALF solution was high for all elements after 2 weeks of testing (e.g. concentrations up to 1,730 mg.kg-1 for As; percentages up to 67.6% for Fe). The solubilisation rate of elements was very high after 2 h, and then declined rapidly and continuously with time. As a result, per cent bioaccessibility increased rapidly and tended to reach a plateau with time. Additional research on the bioaccessibility of toxic elements in PM of geological origin as well as on human health risk characterization is recommended.