Eight percent of newborns in Lake Superior basin show high levels of mercury, according to a recent study  by Minnesota’s Department of Health.

In Minnesota alone, 10 percent of the newborns whose blood was tested for overall mercury showed levels above the Environmental Protection Agency’s reference dose.

Routine blood samples taken from a pool of 1,465 infants born between 2008 and 2010 in Wisconsin, Minnesota and Michigan were tested. The elevated levels found in the infants most likely resulted from pregnant women’s contact with methylmercury, a form of mercury that gets introduced into the food chain via fish.

The presence of methylmercury in newborns is cause for alarm, as it has been shown to have an impact on cognitive functions ranging from memory to motor skills.

“It’s a pretty limited study; we can’t necessarily apply the finding to the whole Minnesota population,” said Doug Schultz of the Minnesota Department of Health, but the results presented “evidence that there’s more work to be done.”

Health-care providers in Minnesota have been pressed to make their patients aware of the risks of methylmercury in fish, especially in the spring and summer, when locals will consume greater numbers of locally caught fish.

Although mercury deposition levels tend to decrease in extreme northern states like Minnesota and Michigan’s upper peninsula, there are problematic species along the southern shore of Lake Superior. The levels for these northern Great Lakes states are significantly lower than areas such as downstate Illinois and Indiana, according to David Gay, coordinator of the National Atmospheric Deposition Program at the University of Illinois.

There was a seasonal pattern in the study as well, showing an elevated concentration in the summer, when fish consumption by pregnant women goes up.
Mercury levels in smaller inland lakes that exceed threshold levels provided for fish consumption and protecting human health..

To avoid mercury exposure, the Minnesota Department of Health advises limiting consumption of some fish, such as bass, catfish and small walleye. For some species, they recommend avoiding them altogether, especially predatory fish like lake trout and northern pike.

Besides identifying species of fish with elevated levels of toxins, the health department also provides a site-by-site advisory for freshwater bodies throughout the state.