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Selenium, Mercury and Suction Dredging -- Studies Contradict California State Water Resources Board

March 16, 2013

There is no doubt that mercury and methyl mercury are hazardous substances when absorbed by humans through contact or when consumed within food in large quantities.

Federal and state regulatory agencies often cite mercury and methyl mercury in our waterways as a major factor for further restrictions on placer mining, and on suction gold dredge mining, in particular.

However, these regulatory agencies are minimizing selenium and its neutralizing effects.

In the Draft Subsequent Environmental Impact Report (DSEIR) on suction dredging published by the California Department of Fish and Wildlife in 2011, the agency calls the evidence of selenium neutralization “lacking” despite numerous studies to the contrary.

The DSEIR reads, “Evidence from laboratory experiments has shown that selenium may be able to moderate the toxic effects of Hg when present at a molar ratio greater than around 1:1, and that most fish in the United States contain high enough levels of selenium to make this a possibility. However, epidemiological support for this phenomenon is lacking, and the limited evidence gives mixed results.”

In contrast to the claims made by the California Department of Fish and Wildlife, numerous scientific studies have shown that selenium—a common element in soils and waterways—binds with mercury and methyl mercury to neutralize it.

Raymond and Ralston, in Mercury: selenium interactions and health implications, state, “Measuring the amount of mercury present in the environment or food sources may provide an inadequate reflection of the potential for health risks if the protective effects of selenium are not also considered. Selenium’s involvement is apparent throughout the mercury cycle, influencing its transport, biogeochemical exposure, bioavailability, toxicological consequences, and remediation.

“Likewise, numerous studies indicate that selenium, present in many foods (including fish), protects against mercury exposure. Studies have also shown mercury exposure reduces the activity of selenium dependent enzymes. While seemingly distinct, these concepts may actually be complementary perspectives of the mercury-selenium binding interaction. Owing to the extremely high affinity between mercury and selenium, selenium sequesters mercury and reduces its biological availability.”

Dr. TW Clarkson of the University of Rochester, New York, published a study on the effects of methyl mercury exposure after nearly fifty years of research. Clarkson concluded that consuming fish that contained typical mercury levels would have no adverse effects.

Scientists who take a more restrictive approach will often cite “Minamata” disease along with a study conducted on Faroe Islanders that revealed high levels of mercury contamination among residents.

Over 3,000 Japanese children were diagnosed with Minamata disease and suffered developmental impairment. The disease was first recognized in the 1950s and was correctly attributed to mercury poisoning from consuming contaminated fish. However, mercury had been dumped into Minamata Bay over a period of 36 years, which made it impossible for selenium neutralization to keep up.

In the Faroe Islands study, the diet consisted of large portions of pilot whale meat. It was discovered that pilot whales—unlike fish commonly consumed in other areas of the world—do not retain sufficient selenium to neutralize mercury concentration.

As mentioned above, California’s regulatory agencies continue to ignore the fact that selenium provides one of the keys to neutralizing mercury in our waterways.

A recent letter, dated March 11, 2013, from the State Water Resources Control Board to Charlton Bonham, Director of the Department of Fish and Wildlife, states, “Based on the water quality impacts of recreational suction dredging, we recommend that the existing moratorium be continued indefinitely, or that this activity be permanently prohibited.

“The resuspension and discharge of mercury is a potent neurotoxin that is harmful to both humans and wildlife. Mercury builds up in the bodies of fish that live in waters with even small amounts of mercury; and in the bodies of humans who eat contaminated fish.”

Ignoring the studies on selenium and its benefits allows the agencies to continue down the path of restrictions, regulations and prohibitions.

There is one more study I want to bring to your attention. A 1995 study (Salonen, et al) revealed that men in eastern Finland consumed large quantities of freshwater fish and were suffering from higher rates of coronary heart disease, so the study examined mercury and selenium intake. Soil testing revealed that selenium levels were extremely low—the lowest in all of Europe—so the citizens suffered from low levels of selenium. Finland found a simple solution—instead of banning fishing and the consumption of fish, it required that selenium be added as a supplement to fertilizers. This simple solution added selenium in waterways due to run-off and sufficiently increased selenium levels in individuals through consumption of fish and other local foods.

Suction Gold Dredges Are Part of The Solution!

Common sense dictates a two-part solution. First, introduce selenium. Selenium levels could be increased in fertilizers with minimal cost. It's already been proven to have a positive effect in Finland.

Second, encourage suction gold dredging. Yes, you heard that right. There is mercury in our waterways, some of it from historic mining activities. There is no dispute on this fact. Historic miners did not foresee the problems they were creating for future generations when they used mercury for capturing gold, but today’s miners have a solution.

Mercury in our waterways is going to be disturbed and transported whether or not suction gold dredgers are in the water. During a large storm, an entire riverbed can be scoured to bedrock, and all material—including mercury—is on the move. Some of that mercury will become methylated.

Mercury is heavy and is attracted to gold, so much of it is captured along with the gold in the riffles of a dredge. Even if a dredge captures only 97% of the mercury it sucks up, it’s logical to allow suction gold dredgers to capture and remove it from our waterways before it gets disturbed by fast moving waters and enters the food chain.

Allowing dredgers to remove mercury from our waterways will benefit the environment and give a boost to the economy in tough times.


(Links are provided where available)

Salonen JT, Seppanen K, Nyyssonen K, Korpela H, Kauhanen J, Kantola M, et al.; “Intake of mercury from fish, lipid peroxidation, and the risk of myocardial infarction and coronary, cardiovascular, and any death in eastern Finnish men,” Circulation 1995 Feb 1;91(3):645–55.

Laura J Raymond, PhD; Nicholas VC Ralston, PhD; “Mercury: selenium interactions and health implications,” University of North Dakota, Grand Forks, North Dakota, USA.

Myers GJ, Davidson PW, Cox C, Shamlaye C, Cernichiari E, Clarkson TW; “Twenty-seven years studying the human neurotoxicity of methylmercury exposure,” Environ Res Section A 2000;83:275–85.

Draft Environmental Impact Report, Chapter 4.2, Pg 53, California Department of Fish & Wildlife, 2011.

Weihe P, Grandjean P, Debes F, White R.; “Health implications for Faroe islanders of heavy metals and PCBs from pilot whales,” Sci Total Environ 1996;186(1–2):141–8.

Selenium and Mercury—Fishing for Answers, National Oceanic and Atmospheric Administration Fisheries Service Pacific Islands Regional Office, U.S. Department of Energy’s National Energy Technology Laboratory, the Energy & Environmental Research Center’s Center for Air Toxic Metals® at the University of North Dakota, 2007.

California State Water Resources Control Board letter dated March 11, 2013, to Charlton Bonham, Department of Fish and Wildlife.

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