USGS's Study on Mercury in Fish: Trouble in the Water

by Catherine O'Neill

August 20, 2009

The United States Geological Survey (USGS) issued a report today finding widespread mercury contamination in U.S. streams. The USGS found methylmercury in every fish that it sampled – an extraordinary indictment of the health of our nation’s waters. The USGS reported that the fish at 27% of the sites contain mercury at levels exceeding the criterion for the protection of humans who consume an average amount of fish, as established by the U.S. Environmental Protection Agency. But EPA’s criterion grossly understates the risk to those people whose fish consumption practices differ from those of the “average American,” particularly members of the various fishing tribes, Asian-Americans, and those hailing from the Pacific or Caribbean Islands. Whereas EPA’s criterion is based on the assumption that people eat 17.5 grams per day of fish – about one fish meal every two weeks, on average – people in these groups consume fish at several times this rate. Many Native peoples in the Pacific Northwest, for example, currently eat hundreds of grams per day. The USGS findings are thus all the more troubling when one considers these higher-consuming populations – the USGS numbers mean that few of the fish sampled are fit for consumption by these people.

The concern raised by widespread mercury contamination in fish is even more pressing in these tough economic times. This summer, more and more people throughout the United States looked to fish for food (Update: for more on this, see Reuters, La Crosse Tribune, Detroit Free Press, and New York Daily News). This makes perfect sense: if they aren’t contaminated, fish are good for you. Nutritionists continue to extol the health benefits of eating fish. Fish are an excellent source of protein, omega-3 fatty acids, and a host of other nutrients essential to human health. And, if one can drop a line or dip a net into nearby waters, fish can be a relatively inexpensive way to put dinner on the table for one’s family.

But those fishing for food are placed in a bind. The USGS findings add weight to other studies that have led federal, state, and tribal governments to issue fish consumption advisories warning people to reduce or eliminate fish entirely from their diet due to mercury contamination. In fact, 48 states have issued advisories placing some or all of their lakes, rivers, or coastal waters under advisory for mercury (see the EPA's site on this).

The existence of this “bind,” in fact, helps explain why advisories actually don’t work to protect public health. For some people, there are simply no other options but catching and eating fish. This is one reason why I have argued elsewhere that agencies charged with protecting human and environmental health should not rely on such advisories and similar “risk avoidance” measures – approaches that ask people to change their ways in order to avoid being exposed to pollution that is permitted to contaminate our fish, water, and air. Instead, these agencies should look to the sources of pollution and require them to clean it up or, better, prevent it in the first place.

Mercury pollution is a case in point. The main anthropogenic sources of mercury releases in the United States are coal-fired power plants. Instead of requiring these sources to reduce their emissions, the Bush Administration notoriously pulled out all the stops to thwart regulation that EPA had had in the works at the end of the Clinton Administration. The Bush Administration’s effort was so out of line with what was required under the law that the D.C. Circuit threw it out. Sadly, we have lost eight years as a result. This delay is deeply troubling when one considers that methylmercury is a neurodevelopmental toxin. Exposure to even small amounts in utero or during childhood can lead to irreversible neurological damage. But evidence shows that at least one in ten women of childbearing age in the U.S. has blood mercury at levels that pose a risk to a developing fetus; and this number nearly triples for the group of women that includes Native Americans and Pacific and Caribbean Islanders So, while the Bush Administration did what it could to thwart mercury regulation, several birth cohorts came into a contaminated world.

The EPA is now trying to dig out from the hole in which they were left, working to craft a mercury regulation for coal-fired power plants. There are other sources, too, that have been left largely unregulated regulated: chlor-alkali plants and gold mines among them. Let’s hope that through legislation and regulation, our leaders will take seriously their obligations to protect the health of all those who rely on fish.

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