Characterizing the Carcinogenic: A Community-Based Participatory Research Approach to Probabilistic Risk Assessment of Metal(loid)s in a Rural, Mining Community

The “Gold Country” region of California is impacted by legacy and active gold mines associated with the California gold rush. Concomitantly, Gold Country has an increased rate of female breast cancer relative to the state average. The study titled “Breast Cancer Risks from California’s Gold Mining Legacy,” a continuation of the ongoing Community Health Impacts of Mining Exposure (CHIME) project, is sponsored by the California Breast Cancer Research Program. Together, researchers from Sierra Streams Institute, University of California San Francisco and University of Arizona are working together to determine whether: (1) breast cancer incidence is higher in closer proximity to mine sites, and (2) arsenic and cadmium exposures are associated with the consumption of local foods, gardening, and trail use in areas with mining residue. Previous research indicates the female population of Gold Country California may face elevated body burden of arsenic and cadmium, which are known to be associated with gold mining wastes, and that this burden is associated with certain behaviors such as gardening and outdoor recreation. Working with community partners and using community based participatory research methods, we recruited 40 participants and collected 354 total samples of water, home-grown foods, soil, and dust, which we compared to standards from the U.S. Environmental Protection Agency, the California Environmental Protection Agency, the U.S. Department of Housing and Urban Development, and the United Nation’s Codex Alimentarius. Using this dataset in conjunction with participant survey data, we conducted a Markov Chain Monte Carlo based probabilistic site-specific risk assessment for residential exposure to arsenic, cadmium. We find that arsenic exposure, due largely to water (63.5%) and home-grown food (33.3%) consumption, presents carcinogenic risks in excess of the EPA recommended upper limit for contaminated sites (1 x 10-4) in 12.5% of cases, and exceeds a risk level of 1 x 10-6 in 98.0% of cases. Analysis of plant metal(loid) data indicates differences in both plant metal(loid) concentrations as well as bioconcentration factors by family. Personalized data sharing materials were prepared and distributed to participants. In addition to detailed figures explaining contaminant concentrations by media, a table was generated outlining how much a participant can eat from their garden based on three different target risks. Our results indicate the need for further research on arsenic, cadmium, and lead exposures and sources in the Gold Country region as well as refinement of risk assessment methodologies, particularly estimation of plant ingestion and increased availability of dose-response data for cadmium and lead