After many years of working with the community to collect environmental monitoring data, we are now working to connect the dots between the health of the environment and that of the humans who live here.
The counties encompassing the Gold Country have consistently higher age-adjusted rates of breast cancer than the rest of the state. In fact, the three most populous of these counties (Nevada, Placer, and El Dorado) have incidence rates in the top 10 of California counties, while the combined incidence in Mariposa and Tuolumne counties is the second highest in the state. This runs counter to the trend of lower breast cancer rates in more rural areas.
Among the many possible reasons for the high incidence of breast cancer in the Gold Country is exposure to mine waste. Mine waste contains the elements cadmium and arsenic, which are carcinogenic metalloestrogens considered provocative with respect to breast cancer etiology.
In the CHIME pilot study—an example of community-based participatory research—sixty women from the local area volunteered to have SSI measure the amount of cadmium, arsenic, and other metals in their bodies. We wanted to know if any residential or lifestyle factors—sociodemographic characteristics, length of residency in Gold Country, residential proximity to mine waste, or daily and recreational activities—are associated with increased levels of these metals in local women's bodies.
The women were divided into two age groups—18 to 35 and over 35—and then divided again according to length of residency in the Gold Country. Each participant provided samples of urine and toenails and told us about her diet, and regular activities, and residential history.
The results of the study have proven to be interesting and to warrant a second follow-up study. Arsenic levels in the urine of the CHIME study participants were higher, overall, than for similarly aged women in U.S. Levels of inorganic arsenic (which is more toxic than organic) was over the level of concern (>20 ug/L) in the urine of six participants, although retests came in below the level of concern for all six. Arsenic levels were highest in women who ate seafood within three days of providing samples or who consumed locally-grown produce at least once a week.
Cadmium levels in the urine of the CHIME study participants were lower, overall, than for similarly aged women in U.S., but women over age 35 who have lived 10 or more years in the Gold Country had significantly higher urinary cadmium levels. Cadmium levels were higher in women living on dirt roads or with outdoor pets.
No cadmium or arsenic levels measured in this study suggested acute toxic exposures requiring medical intervention.
The second CHIME study is an effort to continue to engage the community in an investigation into the health consequences of living in a mining-impacted community.
In this study, we plan to compare the body burden of cadmium and arsenic in women with and without breast cancer. We also plan to train participants on how to collect soil and water samples that can be used to measure exposures in the home environment.
After completing this second CHIME study, we plan to expand our investigation into other parts of the Gold Country, study other health outcomes related to mining contamination, and Intensify environmental sampling to better identify routes of exposure.