MINNEAPOLIS (WCCO) — Minnesota researchers conducted the first ever study of its kind, looking at mercury exposure levels in newborn babies.

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The Minnesota Department of Health set out to see how much mercury newborns have in their blood, since small amounts can harm tiny brains and developing nervous systems.

In 2008, researcher Pat McCann started the project, testing 1,465 babies’ blood samples from the state newborn screening program in Minnesota, Wisconsin and Michigan.

McCann says the majority of babies had little exposure, but overall, 8 percent had unsafe levels of mercury. In Minnesota, however, the results were higher with 10 percent of babies with unsafe levels of mercury.

No Michigan samples were above the U.S. EPA dose limit, and 3 percent of the Wisconsin samples were above the limit, according to the report.

Babies born in the summer had higher levels than those born in the winter, which led McCann to look deeper at how much fish is eaten in Minnesota, since fish consumption is higher in the summer.

“Some studies have reported that people in Minnesota eat more fish than Wisconsin and Michigan as you might expect, also walleye and northern along north shore of Lake superior Basin are more contaminated in mercury than other parts of the state,” said McCann, who added that it’s clear the exposure to infants in Minnesota is too high.

The pollutant is environmental and can be distributed by wastewater treatment plants, mining and coal fired power plants.

New mothers at the Amma Parenting Center in Edina say they learned preventing mercury exposure begins even before pregnancy.

Patricia Kendrick of Edina knew to practice one guideline when she was pregnant.

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“I limited it to once a week for fish, which is hard when you love fish,” she said.

Michelle Ugurlu of Plymouth said she followed Minnesota Department of Health Guidelines when she was pregnant with her 3-month-old daughter Hazel.

“I was given a pamphlet that told how much I could fish I could have at a time, certain types, large fish versus small fish, fresh water versus salt water,” said Ugurlu, who says she’ll monitor even more closely with her next child. “I hope that the literature gets out to new moms and expectant moms.”

The Minnesota Department of Health has safe fish eating guidelines for women of child bearing age and children under the age of 15.

McCann says women should still eat fish, which is good for developing babies, but eat fish low in mercury. She says the general rule of thumb is to eat smaller fish, since large predator fish that eat other fish have more mercury.

“Because they haven’t lived as long, they haven’t had time to accumulate as much mercury,” said McCann, who warns that predator fish have higher levels.

“Walleye and Northern because they are at the top of the food chain and have the most mercury, “ she said.

Fish like salmon and shrimp and tilapia you can eat twice a week.

If you like canned light tuna or sunfish from our lakes, you can eat once a week. Once a month, it’s OK to eat fish like halibut, or smaller walleye and northern pike.

Fish to avoid In Minnesota include walleye longer than 20 inches and Northern Pike longer than 30 inches. As far as ocean caught fish, avoid shark and swordfish.

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Read more on the study here.