Toxic metal(loid)s such as arsenic pose environmental hazards to human and organisms’ health in locations throughout California where metal mine tailings are located near residences and ecosystems. However, the relationships between the geochemical/physical properties of airborne dust particles and the bioaccessibility/bioavailability of potentially harmful elements in the particles has not yet been clearly established, precluding a basic understanding of the potential correlations between dust composition, speciation and particle toxicity, thus impairing risk assessment efforts in impacted regions. The bioavailability of inhaled arsenic is largely dependent upon two factors: the size and solubility of the arsenic-bearing particle, showing how far into the tissues the potential arsenic-containing particles will be lodged, and how rapidly the arsenic is absorbed into the bloodstream and organs. Our research aims at determining the bioaccessibility and bioavailability of mine tailings samples in the respirable (≤10 µm) size range. Rats were exposed to an acute dose (1000 µg/m3) of airborne particles from two mine waste sources from the Marigold East gold mine in California for a period of 3 hours, then sacrificed immediately after exposure and after 1 and 7 days post-exposure, with results compared with a control group that was not exposed. Arsenic concentration was measured in the urine, feces, blood, and a range of tissues and analyzed for the application to human health risk. The feces and urine analyses, which were collected both before and after exposure, allowing greater temporal resolution, showed an initial sharp increase in arsenic in the 1st day post-exposure, followed by a decrease to background arsenic levels by day 3-4, followed by a gradual increase in arsenic through day 7. The tissue data, collected at days 0, 1, and 7, show comparable trends but to varying degrees. The results suggest that arsenic is released from the mine wastes in two stages: a rapid release of highly soluble, surface-bound arsenic, and a slower release of less-soluble, particle-bound arsenic. The mine tailings do demonstrate higher bioavailability than the waste rock suggesting that processing produces more soluble arsenic phases. The experimental knowledge generated is expected to be transferable to other environmentally-contaminated regions where fine-grained dusts have the potential to be mobilized and inhaled, increasing hazardous exposure to residents.

Correlating arsenic bioaccessibility & bioavailability through in vivo rat exposures

253rd National Meeting (2017)

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