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UW-Madison research part of international mercury conference

University of Wisconsin-Madison

A number of University of Wisconsin-Madison scientists will present research at the Eighth International Conference on Mercury as a Global Pollutant starting this weekend at the Monona Terrace Community and Convention Center in Madison.

Here is a preview of some newsworthy presentations:

Fish Advisories in Context:
Tuesday, Aug. 8, 4:40 p.m., Ballroom C: A UW-Madison researcher has found that fish toxicity notices in Wisconsin are often ineffective and largely fail to inform consumers about the dangers of mercury-contaminated fish.

Maria Powell, a research associate at UW-Madison's Lafollette School of Public Affairs, explored fishing cultures among African-American and European fishermen in Milwaukee and Cleveland. Powell looked primarily at how socioeconomic, physical and cultural factors might be influencing how fishermen perceive public notices about fish health.

The researcher found varying levels of trust with regards to the notices. Also, pro-fishing marketing and media coverage often overwhelms the coverage of the fish advisories, deepening confusion in the community.

Powell discovered the situation is even worse within the state's Hmong populations, which barely receive notices to start with. Additionally, myriad social, cultural and technological constraints bar Hmong community members from accessing the few translated notices that are available.

Powell believes fish-contamination notices could be have more impact with increased funding for their creation, improved communications with uninformed communities and better media coverage of fish contamination issues.

CONTACT: Maria Powell, (608) 240-1485,

Attacking mercury through the food chain:
Tuesday, Aug. 8, 10 a.m., Grand Terrace: To address the problem of mercury contamination in fish, a UW-Madison scientist is hunting for the microorganisms that help mercury slip in to aquatic food chains.

Geo-microbiologist Eva Sedo is focusing the search on members of a bacterial family known as the "sulfate-reducing bacteria" group. Researchers know that many sulfate-reducing bacterial species can produce methylmercury - the form of mercury most likely to contaminate fish - but it's still unclear which species produce the greatest amounts of the toxin.

Sedo says strategies to prevent mercury contamination will be limited unless scientists gain a deeper understanding of the sulfate-reducing bacterial community. She hopes to further that understanding by studying organisms in the Florida Everglades and in northwestern Ontario, Canada. Sedo has collected dozens of sulfate-reducing species from those sites to gauge how much methylmercury each is able to produce.

CONTACT: Eva Sedo, (608) 217-3190,

Consequences of exposure to methylmercury during development:
Tuesday, Aug. 8, 10 a.m., Grand Terrace: Pregnant rats that were exposed to a potent form of mercury gave birth to offspring that later showed problems changing their behavior to adjust to changes in their environment. A diet of fish oil - which some people think might counteract these consequences of methylmercury exposure - did not help the rats overcome their behavioral problems as they aged.

Elliott Paletz, a researcher with the UW-Madison Department of Psychiatry, tested the long-term consequences of in utero exposure to methylmercury, a common and highly toxic form of the metal. Exposure to methylmercury during development is known to cause serious neural and behavioral problems for many animals later in life.

Paletz says adult rats that had been exposed to methylmercury in utero were able to learn specific tasks - for example, pushing a lever when a light was turned on when they received food as a reward. However, the rats encountered problems when the tasks changed even slightly. Paletz describes the problems as "behavioral rigidity." The rats struggled to learn new behaviors even though they would be rewarded for them, and they persisted in old behaviors even when rewards were no longer offered.

Some rats in the experiment were raised on a diet that was rich in fish oil, specifically an omega-3 fatty acid known as DHA (docosahexaenoic acid). Some people suggest DHA might ease the neurotoxic effects of methylmercury, but DHA did not ameliorate the effects of methylmercury in this study at all. When rats on this diet were tested at middle age (about 15-18 months), they committed a substantial number of errors. (Intensive behavior therapy during the experiment mitigated these effects, and even the most seriously affected rats did well after this intervention.)

Paletz says the findings suggest that methylmercury produces behavioral rigidity in rats and that fish oil does not mitigate these effects. He says the findings have potential implications for human health: the children of women who were exposed to methylmercury during their pregnancies might have impairments that affect them later in life whenever "the rules change" in learning situations.

Paletz conducted this research for his Ph.D. dissertation at Auburn University.

CONTACT: Elliott Paletz, (608) 262-4780,

Methylmercury in groundwater in a Lake Superior watershed:
Wednesday, Aug. 9, 2006, 10 a.m., Hall of Ideas: Mercury contaminates watersheds around Lake Superior, and naturally-occurring bacteria convert this mercury into its most toxic form - methylmercury. Scientists have known for many years that these toxic transformations occur in wetlands and lake sediments: studies in Michigan's Upper Peninsula documented similar transformations in groundwater. Researchers from UW-Madison worked on a team that found that methylmercury levels in the watershed of the Tahquamenon River were elevated during periods when most of the water was coming from groundwater, not surface runoff.

The findings of this research suggest that the methylation process occurs amidst the rocks and gravel at the bottom of streams and in the sandy landscape that underlies coniferous forests in the Upper Peninsula. However, these findings are not specific to just Lake Superior and the Upper Peninsula: they confirm the importance of groundwater as a source of methylmercury to watersheds around the Great Lakes.

CONTACT: James Hurley, (608) 262-1136,

Bioavailability of Mercury in the Great Lakes Basin:
Thursday, Aug. 10, 10 a.m., Grand Terrace: Many fish in the Great Lakes Basin are contaminated by the most toxic form of mercury - methylmercury - and government health agencies issue fish consumption advisories to limit public exposure to this contaminant. The concentration of methylmercury in fish is not necessarily connected to the concentration of mercury in their immediate surroundings. Much of the methylmercury that enters Lake Michigan from tributary rivers appears to come from watersheds with large wetlands, not heavily industrialized regions. In addition, the mercury that contaminates sediments in waters around one industrial area - the city of Green Bay, Wis. - appears to be bound to the sediments in a way that keeps it from undergoing processes that otherwise would transform it into a more toxic form.

The transformation of mercury into methylmercury is caused by bacteria, and this process has been documented in wetlands and in sediments of lakes. This natural process appears to be creating more methylmercury in wetlands around Lake Michigan than in heavily industrialized areas. The situation in the waters around Green Bay, Wis., might be unique to the area. The form of mercury that has entered the Fox River - possibly from industrial uses - apparently binds very tightly to sediment particles, and this has obstructed the methylation process in parts of the Fox River and in portions of Lower Green Bay.

CONTACT: James Hurley, (608) 262-1136,


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