Summary of environmental mercury concentrations and assessment of risk to public health from mercury at the geysers

Altshuler, Sam L.
Robertson, Moire L.
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Pacific Gas and Electric Company, Department of Research and Development
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Ambient mercury data were investigated in relation to the environment and public health at and near the vicinity of The Geysers, California. Mercury was found to occur naturally in the environment (air, water, soil, etc.) and as a result of industrial activities, although the exact contribution of each source could not be determined. Ambient air concentrations ranged from non-detectable to 630 ng/m3 . Concentrations in ambient waters ranged from non-detectable to 2.9 Mg/1; the highest value exceeds all water quality criteria for the protection of health and is 30% below the level set to protect freshwater organisms from acute toxicity. Little data are available on concentrations of mercury in fish; however, the existing data suggest that some fish may be bioconcentrating the mercury. Reported data for mercury in fish were above applicable health standards (for food) in most cases. Soil mercury levels ranged from less than the detection limit to 11 Mg/g. Mercury was not detected in small animals, and low and relatively insignificant mercury concentrations were found in bulk atmospheric deposition samples and in foliage. Because total human exposure data in or near The Geysers area are not available, the above environmental data were compiled and used to assess the worst-case potential risk to public health as a result of mercury emissions (natural and industrial) at The Geysers. The results of this study show that the highest mercury exposure to humans occurs from ingesting inorganic mercury in food. The concentrations of mercury in food are not expected to be impacted by activities at The Geysers. Under normal conditions. mercury in food accounts for approximately 99% of the total exposure to mercury. Regardless of the route of exposure (air, water, or food), the daily total exposure of mercury to the public living at The Geysers is predicted to be 28 Mg/day. According to the EPA, national average mercury exposures are approximately 25 Mg/day. It is very unlikely that any public health effects would occur since exposures of 200 Mg/day of methyl mercury are necessary for toxic response to be noticeable.
health, geysers, California, Geothermal resources--Environmental aspects, Environmental impact analysis
Altshuler SL, Robertson ML. 1989. Summary of environmental mercury concentrations and assessment of risk to public health from mercury at the geysers. San Ramon (CA): Pacific Gas and Electric Company.
49 pages
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