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Mercury Levels Safe in Waters of California's Gold Country

June 12, 2013

The California Water Board recently released the results of an extensive study that’s good news for California fishermen. The most comprehensive study yet of California sport fish indicates they are safe to eat throughout the Sierras.
New Study Released
The study was the third in a three-part study extending over seven years that sampled 63 rivers and 568 fish to determine the health of California sport fish.
Without exception, the fish in the mountains and gold-bearing areas of California were either well below or significantly below established criteria for consumption. Eighty-seven percent of locations sampled tested below mercury threshold levels and 100% of rivers in the gold country tested below US Environmental Protection Agency (EPA) thresholds. The only areas found with levels of mercury exceeding advisory criteria were in the Sacramento Delta, which is consistent with earlier testing.
The Water Board report concluded, “This could indicate that safe fish consumption at a frequency of more than one serving per week is possible at the vast majority of these locations if the cleaner species are selected. Comparing the data to a high standard of safety, 28 of the 63 locations (44%) had at least one species that can be safely consumed at a higher consumption rate of 3 servings per week.”
Confirms Prior Studies
The results are consistent with earlier studies finding California trout are some of the safest for consumption in the country. Measured amounts of toxins, including mercury, show levels well below established health advisories. This new information throws into question the continued push by environmental groups to place additional restrictions on fishing and outdoor activities.
The study follows a 2007 study of reservoirs and lakes that found none of the 22 lakes sampled required California Office of Environmental Health Hazard Assessment advisories. The study also found no difference in mercury levels between lakes in or outside historic mining districts.
The Water Board studies reflect a continuing trend in California for decreasing mercury levels. A 2011 US Geological Survey (USGS) report on mercury levels across the United States found mercury levels across the West had been dropping, including over a 7% drop in mercury levels in the Sacramento River and a 3% drop in the Klamath River. The USGS study evaluated measurements from a span of twenty years.
The Water Board study also measured levels of the naturally occurring element selenium. According to newly released guidance from the US National Oceanic and Atmospheric Agency (NOAA) the presence of selenium acts to completely offset the effects of mercury. The new NOAA guidance states if the balance of selenium to mercury in fish is achieved then fish are safe to eat. The Water Board study found levels of selenium in the fish exceeded the levels of mercury indicating an additional safety factor for consumption. 
“These studies confirm what we’ve been saying,” said Western Mining Alliance President Craig Lindsay. “Despite the rhetoric of environmental groups claiming a toxic legacy from mining, there is no argument about the science. The data clearly shows mercury is not an issue in gold country, the fish all measure well below advisory criteria, and mercury levels have been consistently dropping over the past twenty years.”

While the Water Board documented the selenium levels in fish and noted they exceed the levels of mercury, they have yet to acknowledge the numerous scientific studies that show selenium effectively neutralizes the effects of mercury. This selenium-mercury connection was conveniently ignored in the Draft Subsequent Environmental Impact Report on suction gold dredging in 2011 . (See: Selenium, Mercury and Suction Dredging -- Studies Contradict California State Water Resources Board, ICMJ's Prospecting and Mining Journal, March 16, 2013.)

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