Artisanal and small-scale gold mining (ASGM) has proliferated in recent decades due to the rising price of gold. Some sixteen million people are now estimated to be involved, primarily in rural areas of low and middle income countries. Most of these mines rely on mercury amalgamation to concentrate and liberate gold. Although environmental exposure to metallic mercury can result in a variety of adverse neurological health outcomes, there are typically no occupational or environmental safeguards. Worse yet, the mercury amalgams are sometimes vaporized in private homes, which are very small, confined “huts”, thus exposing children and potentially pregnant women.
As part of an effort to assess mercury exposure while educating miners and villagers about safeguards and altogether safer alternatives to mercury, CUNY Graduate School of Public Health and Health Policy (CUNY SPH) Professors Glen Johnson, Jean Grassman, and Jack Caravanos (now with the NYU College of Global Public Health) secured funding from a CUNY Collaborative Incentive Research Grant to visit a high altitude ASGM site in the Bolivian Andes. The faculty were accompanied by CUNY SPH master’s students Yilmael J. Diaz and Lina Hernández Gutiérrez, along with Guido Condarco from Fundación Plagbol, La Paz Bolivia, who established all local connections and transportation.
Elevated mercury levels were detected in localized concentrations where it is used for processing the gold ore, but fortunately it became non-detectable just a few meters away from its source and was not detected in the local village. Arsenic, however, was elevated at every sample point in both the mine processing center and the local village, exceeding the EPA screening level for remediating industrial soils. The researchers’ work documents very high levels of soil arsenic, which is known to be naturally high in the Andean region due to volcanic geology. However, Johnson explains that “arsenic levels far exceeded local background values in locations where mercury was also the highest, indicating increased arsenic exposure where gold ore is processed” and aresenic is released as a result. Several arsenic measurements were extraordinarily high, with soil concentration ranging from 5-14%.
The researchers collaborated with Brian Pavilonis, also a professor at CUNY SPH, to release a formal human health risk assessment which was published earlier this year in the journal, Environmental Research. The Bulletin of Environmental Contamination and Toxicology has also published their report which characterizes the spatial distribution of surface soil mercury and arsenic.
Aside from contributing to the literature on mercury and arsenic levels at high altitude mining sites, the paper also illustrates how geo-spatial methods can be used to leverage limited data in a very remote location with no pre-existing spatial data.
“This work contributes to the understanding of occupational and environmental exposures to mercury at artisanal and small scale gold mining sites where mercury is used to extract gold. However, much remains to be done to reduce metals exposure to miners and villagers, including children, as this type of mining proliferates globally, largely within low and middle-income countries,” concludes Johnson.
Johnson GD, Pavilonis P, Caravanos J, Grassman J. Geo-spatial Characterization of Soil Mercury and Arsenic at a High-Altitude Bolivian Gold Mine. Bulletin of Environmental Contamination and Toxicology. First online 16 Nov 2017.