12/10/02

AUBURN RESEARCHERS INVESTIGATE MERCURY'S 'SILENT' DAMAGES

AUBURN -- A team of Auburn University researchers is investigating whether prenatal exposure to highly toxic methylmercury causes "silent" brain damage that isn't apparent until late adulthood.

The study's findings could be used by federal agencies that are reviewing their dietary advisories for pregnant women regarding fish and seafood and will become part of the heightened national focus on the risks versus the benefits of eating fish. Humans are exposed to methylmercury mainly through fish in the diet.

The research project, funded by the National Institute of Environmental Health Sciences and the Auburn University Environmental Institute, brings together AU researchers from three disciplines: Christopher Newland, Alumni Professor of psychology; Elaine Coleman, College of Veterinary Medicine associate professor; and Margaret Craig-Schmidt, a professor in the College of Human Sciences.

Newland recently completed a similar mercury research project that indicated that gestational exposure to methylmercury has long-term physical effects that do not appear until late middle age. Most notably, mercury-exposed rats in the study aged faster than non-exposed rats.

"They didn't die earlier, but their bodies began deteriorating and they began their physical decline at a younger age," Newland said.

The new research project will attempt to replicate Newland's earlier findings and to extend them to numerous behavioral domains, including visual function.

Because methylmercury affects the development -- and, evidently, the aging -- of the brain, the AU study's findings could also contribute to scientists' growing understanding of how the brain and behavior change in the course of a lifespan.

As part of the Auburn, the researchers also will investigate whether the risks associated with methylmercury might be offset by certain key nutrients found in fish. Foremost among those nutrients are omega-3 fatty acids, which are vital to central nervous system development in the prenatal and infant stages and which also lower cholesterol, blood pressure and risk of heart attack in adults.

"There's a great deal of uncertainty out there about whether methylmercury's adverse effects outweigh the many benefits of omega-3 fatty acids and other nutrients found in fish," Newland said. "We hope our work will help clarify those issues."

In the AU researchers' multidisciplinary study on rats, Newland is assessing the subjects from a behavioral standpoint, including mercury-exposed adult rats' reactions to movement and flickering lights.

Coleman is investigating whether the gestational exposure to mercury affects the neurons in the brain that underlie learning. Craig-Schmidt, meanwhile, is designing the diets the rats are fed, including one that is rich in omega-3 fatty acids and other nutrients found in fish and another that lacks those nutrients.

Mercury is released into the air by coal-burning power plants, municipal waste and hazardous waste combusters, and medical waste incinerators. Tiny mercury particles fall into waterways, where they are converted by bacteria into the toxic methylmercury.

The substance accumulates in fish muscle over time, so long-lived predatory fish-- namely shark, swordfish, tile fish and king mackerel -- contain the highest concentrations of methylmercury. Newland said he recommends that all individuals eliminate those four species from their diets.

Two federal agencies -- the Food and Drug Administration and the Environmental Protection Agency -- have warned pregnant women, nursing mothers and women of child-bearing age who may become pregnant that by eating mercury-containing fish, they run the risk of damaging their infants' central nervous system during critical developmental stages.

The FDA advisory urges those women to eat no more than 12 ounces of fish a week and to completely avoid the four species known to have high concentrations of methylmercury.

"Fish are an important part of a balanced diet, and my concern is that such advisories may drive some people away from eating fish altogether," Newland said. "But if they stop eating fish and instead eat french fries, which is worse?

"Better information for the public must be provided, and to do this we need a better understanding of how nutrients and toxic substances act on the developing and aging brain," Newland added.

The Environmental Institute serves a clearinghouse for environmental research, outreach and instruction at AU. The institute's key mission is to facilitate a multidisciplinary approach to environmental problem solving.

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dec02:AU-mercury

CONTACT: AU Environmental Institute, 334/844-4132.