High mercury levels found in US streams and fish

MANUEL RUEDA, Anchor: Scientists from the US Geological Survey have found widespread mercury contamination of fish in streams across the country. The researchers published the “Report on Mercury in Stream Ecosystems” this week, which says that mercury was found in every fish tested in nearly 300 streams.

According to the study, more than 25 percent of the fish had levels of mercury higher than EPA safety levels establish for fish consumption. The scientists also looked for mercury levels in water and bed sediments.

FSRN spoke with Lia Chasar, a researcher at the US Geological Survey and one of the scientists who worked on this report.

Your study detected mercury contamination in every fish sample in 291 streams across the country, but how high were these mercury levels in the fish and were they also high in bed sediment and water?

LIA CHASAR, USGS researcher: The mercury levels in fish tended to roughly parallel the mercury levels in the water across the nation. Mercury levels in water are much lower than they are in fish by sometimes as much as a million times, because mercury does magnify as it goes form water to fish. But the levels range from fairly low values over the country to values that were higher than the EPA consumption criteria for fish.

RUEDA: Were there lots of fish that were beyond the consumption criteria? Are there any fish people shouldn’t be eating or places where people shouldn’t be fishing?

CHASAR: In our data set for the fish that we sampled, which was across the U.S., we found that for our fish, more than a quarter of them exceeded this safe consumption level of 0.3 ppm.  That’s a criterion that was set by the EPA for no effects.  About a quarter of our samples exceeded this level.  The best thing in terms of whether or not you can know if it’s a safe place to fish and eat the fish is to go to the state and national advisory website that’s hosted by EPA.  If you go to this EPA website, you can find a map and click on your state, and it’ll give all the different water bodies that are monitored in your state and the fish, and it’ll tell you which ones are safe to eat in terms of this EPA mercury criterion, and which ones you should either not eat as much of or stay away from.

RUEDA: Where does the mercury come from? How does the mercury get into the streams and the fish?

CHASAR: Over most of the U.S., mercury comes from what’s called atmospheric deposition.  Mercury is emitted into the atmosphere from things like coal burning power plants, waste incineration, cement production, and chlor-alkali facilities. And then once it gets up into the atmosphere, it can get deposited locally or it can travel a long way. It gets deposited out from the atmosphere in rain, snow, or sometimes just dry particles. Once it gets deposited onto the landscape, then it gets into areas that are wet or wetlands.  There is a type of bacteria that can methalate that mercury, make it toxic. And then it gets from that toxic form into many aquatic organisms, into the algae and fish.

RUEDA: So even if there’s not a coal power plant nearby, the stream may still have mercury in it?

CHASAR: Yes, mercury sometimes deposits very close to where it’s emitted and sometimes it travels a long way, so it’s actually more of a global problem.

RUEDA: Your study tested mercury levels from 1998 to 2005. Do you think the situation is better in 2009 or is it worse?

CHASAR: Well unfortunately, we don’t have a nationally consistent monitoring network in place so we don’t have a way to monitor trends in mercury in fish or water right now. About 10 years ago, for a long period of time, there was a program called the National Contaminants Biomonitoring Program. And they monitored mercury and other contaminants in fish from the late 1960s to the late 1980s. So we have good trend information from that time, but since the late 1980s, we don’t have good trend information.  One of the things that’s sorely needed is this way to nationally, consistently monitor these contaminants in our system.

RUEDA: That was Lia Chasar with the U.S. Geological Survey She says the EPA is currently revisiting the Clean Air Act and measures that could reduce mercury, while Congress is also studying the creation of a mercury monitoring network.  The EPA also publishes regular fish advisories at http://www.epa.gov/waterscience/fish/