National study finds mercury in fish in every stream tested - WKOW 27: Madison, WI Breaking News, Weather and Sports

National study finds mercury in fish in every stream tested

MADISON (WKOW) -- For Lee Loving, nothing is better than an afternoon in Madison while kicking back and waiting for the fish to bite.

"Good eating, especially the walleye," said the Chicago man. "Walleye's really one of the best tasting fish I've ever eaten."

He and his wife often make the trip from Illinois to Lake Monona for a specific reason.

"The fishing is no good where I'm from," said Dorothy Loving. "Because the mercury in the water." She added, "I heard there was some mercury, maybe, in all fish, but you know, fish is really fresh this way."

She didn't know how right she was.  Last month, the United States Geological Survey found there was mercury in every fish it tested in 291 streams across the country.  About one-fourth of the fish had mercury levels higher than what's considered healthy for people who eat fish regularly.

According to that study, some of the mercury pollution out West was due to mining. Closer to home, the likely source is coal-fired power plants.

Mercury is a neurotoxin. Women planning to be pregnant and young children are typically asked to limit how much fish they eat.

"There is a potential for an impact on the central nervous system for consuming too much mercury," explained Department of Natural Resources spokesperson Greg Matthews. The DNR publishes a list of mercury warnings for anglers, along with suggested preparation methods.

This new study by the USGS received pushback from the National Fisheries Institute. That group issued a statement saying: "USGS did not test commercial seafood. USGS tested fish from 'streams across the country.' ... The commercial fish we enjoy in restaurants or buy in the grocery store do not come from streams."

Although many of the people you'll see lining the shore of Lake Monona do eat what they catch.

"I love fish, it's good for you," said Dorothy Loving.

As the Loving's said, walleye is their favorite.

"It does accumulate in the environment," Matthews said of mercury in water. "The bigger the fish, especially the walleye, the bigger chance to have mercury."

So people like this Chicago couple will catch with caution, knowing that the fish here might not be 100-percent pristine either, but their haul will likely be healthier than from where they came.

"I don't know that much about it, but i do know it can be harmful if you do too much," said Lee Loving.

One of the authors of the study is Barbara Scudder from the Middleton office of the USGS.  She declined to speak on-camera, but offered thorough answers to questions from 27 News by email.  Below are her answers:

-What was the point of the study? Our objective was to determine the geographic and geochemical characteristics of stream basins that relate to fish-mercury levels in streams. The main source of mercury to natural waters of the U.S. is inorganic mercury that is emitted to the atmosphere and deposited with precipitation or dry particles. However, atmospheric deposition alone does not explain high mercury levels in fish from our nation's streams. Specific ecological conditions can enhance the conversion of inorganic mercury to the more toxic organic form, methylmercury, which is readily taken up and retained by aquatic organisms. Over 95% of the mercury in fish is in the toxic methylmercury form. Our study involved a one-time sampling of streams across the U.S. for mercury in fish, water, and streambed sediment.

-Why focus on streams (not lakes?) There is a critical need for multi-media studies of mercury in streams, using methods that are comparable across the Nation and consistent through time. Most studies of mercury in aquatic environments have focused on lakes, reservoirs, and wetlands. Fewer studies have focused on streams.

-How surprising was the result that every sample of fish had at least a trace sample of mercury? The detection of mercury in every fish sample was not a great surprise because mercury can be transported long distances in the atmosphere, and the science is such that we are now very good at detecting low levels of mercury. The fact that a quarter of fish samples were above the USEPA mercury criterion was also not surprising because 48 of 50 States have fish consumption advisories. This means that 48 out of 50 States have at least one commonly consumed fish species that exceeds the 0.3 parts per million criterion established by the USEPA for the protection of people who eat average amounts of fish. Mercury is currently the second leading cause of impaired waters in the United States, accounting for over 9,000 impaired waters (as of 26 August 2009).

-Is some mercury in the environment naturally occurring, or is it all appearing from human activities (i.e. mining and coal-fired power plants?) Although there has always been some mercury in the atmosphere from natural sources (volcanoes and degassing of elemental mercury from the oceans), human activities have increased the amount of mercury emitted to, and deposited from the atmosphere. Human-caused sources of mercury to the atmosphere are largely from combustion of materials that contain mercury, with coal-fired combustion being the largest source in the U.S., according to the 1997 EPA Report to Congress (<>).

In 2007, an international panel of experts concluded that remote sites in the Northern and Southern hemispheres show about a threefold increase in atmospheric deposition of mercury since pre-industrial times (Lindberg and others, 2007). In the most remote parts of North America--for example lakes in Glacier Bay, Alaska--current rates of atmospheric mercury deposition are about double what was observed in pre-industrial times (Engstrom and Swain, 1997). In the continental U.S., proximity to more mercury emission sources has resulted even larger increases-typically about threefold to fourfold since pre-industrial rates (Lorey and Driscoll, 1999; Swain and others, 1992; Van Metre and Fuller, 2009).

-What can you actually do with the results of this study? Findings from this study will be helpful to natural resource managers who need to anticipate where they may expect higher mercury levels in fish, water, and sediment from streams. In addition to the occurrence of mercury in fish, we found that there are ecosystems across the US that may be more "sensitive" in terms of mercury accumulation in fish. Sensitive ecosystems are those that were largely undeveloped with evergreen forested watersheds and abundant wooded wetlands.

-Have you heard criticism that it is alarmist to declare that every fish has mercury contamination? Yes, we have heard that criticism, and our intent was not to suggest that people avoid eating fish, which are known to be an important part of a healthful diet. The press release used the word "contamination," which has often been used in the context of a chemical that is present that should not be there (that is, entirely a result of human activities) and in the context of a chemical that is present but undesirable--even if some or all of it is natural (natural arsenic in groundwater is a famous example). The press release used "contamination" in the most generic sense, which could encompass both of these meanings.

We hope that people would use this as an opportunity to educate themselves on the issue: what are their state's fish consumption advisories? Where does the mercury come from? What is being done to reduce mercury in the environment? The best thing people can do is to become informed. Visit websites of the USEPA, FDA, and your State's health agency to find out which fish from which waterbodies in your area are safe or not safe to eat. These agencies provide guidelines so that the public can make informed decisions about which fish species are safe to eat, and they recommend including fish as part of a healthy diet but urge us to choose kinds (species) of fish that are lowest in mercury. They also let us know which fish to minimize or avoid. The USEPA has established a criterion of 0.3 parts per million for methylmercury in fish for the protection of people who consume average amounts of fish (<>). There is also a USGS website on mercury research which has links to summaries on mercury in the environment and current research results for these studies we have just released as well as many others (

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