Exposure Assessment of Children & Metals in Mining Waste

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Project #2 explores the transport and fate of metals from mine wastes (chat) that could potentially lead to adverse exposure in children in communities surrounding the Tar Creek Superfund Site. Although metals in mining waste have been thought by some to be relatively unavailable for geochemical mobilization or biological uptake (due to interactions with reactive sulfides), we hypothesize that reactions releasing metals from the sulfides may make metals from mining waste more bioavailable than expected. They may also favor the release of some metals (such as Zn and Cd) over others (such as Cu and Pb). Thus, the mixture of metals to which children are exposed may be very different from the mixture of metals present in the parent chat. In addition, metals that have mobilized off the chat piles into other exposure media such as soil, water, airborne particulates and indoor dust, may have a higher relative bioavailability when compared to parent waste material. We propose to test this hypothesis, and determine whether the types and bioavailability of metals to which children are exposed can be better understood through a more sophisticated consideration of the underlying geochemistry of metals in mine wastes. Specifically, we will study which metals are enriched in down-gradient exposure media relative to metals in chat, and use sequential extraction techniques (and X-Ray Absorption Spectroscopy) to demonstrate that metals in these down-gradient media have a higher relative bioavailability. In conjunction with Project #1, we will use these data to conduct a nested case-control study to examine the extent that environmental and behavioral factors, including diet and activity patterns, may explain differences in blood levels of Pb and Mn in children from the Tar Creek area with high and low levels of Pb and Mn in their blood. We will use the samples we have collected in this project to supply the animal studies (Projects 3 and 4) with well characterized exposure material with respect to the concentrations and potential bioavailability of metals within each media. Finally, in parallel with the exposure assessment, we will conduct microarray experiments and assess their utility as part of an overall exposure/adverse health outcome assessment.