Elevated arsenic (As) concentrations are pervasive in mining wastes throughout the state of CA, the broader Western US, and globally. Of potential As exposure mechanisms in mining regions, the inhalation pathway is less well understood yet potentially more significant than the ingestion pathway, particularly in semi-arid, windy regions. Additionally, there are relatively few approaches to minimizing airborne particulate exposure compared to exposure through incidental ingestion. Mine tailings (processed ore) and adjacent waste rock (unprocessed material) from the Marigold West Mine in the Mojave Desert, CA were collected in bulk and sieved in the field, through a sieve shaker and an ultrasonic siever to produce ≤10 µm (PM10) particles from each sample. Reactive surface area, initial As concentration, and As chemical speciation were assessed on the PM10 samples with BET surface area analysis, acid digestion/ICP-OES, and X-ray absorption spectroscopy. In vitro As bioaccessibility was determined using a 6-day phagolysosomal simulant fluid extraction followed by filtration and ICP-OES analysis of dissolved As. A nose-only inhalation exposure system was applied to expose Fischer 344 rats to aerosolized particles from both mine tailings and waste rock at a concentration of 1 mg/m3 for a period of 3 hours. Cohorts of five rats were sacrificed immediately after the exposure (Day 0) and 1 day and 7 days post-exposure, with an additional control non-exposed cohort sacrificed on Day 0. Blood, heart, lung, liver, and kidney samples were collected from sacrificed rats, and urine and feces were collected over the course of 7 days from various cohorts. Lung As concentrations were elevated immediately after exposure and declined over the next 7 days, confirming that inhalation of respirable PM10 particles led to detectable As in the lung. Correspondingly, blood As concentrations increased at day 1 and declined by day 7, suggesting the transfer of soluble As from the lung into systemic circulation. Liver and kidney As levels similarly showed a rapid increase followed by a slow decline over 7 days. In most cases, mine tailings exposure resulted in greater degrees of mobilized As compared with waste rock exposure. Urine and feces As concentrations both increased post-exposure and declined over the next 5 days, with urine levels rising again by day 7 suggesting two phases of As release, one from a soluble As species and another from a more slowly-soluble species.

Bioavailability of arsenic in PM10 mine wastes through a nose-only inhalation exposure model

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.