By Sarah Coefield
Oct. 15, 2009

The Great Lakes teem with fish, but anglers looking to them for their next meal should be cautious.

The fish contain an array of contaminants, including some known to threaten human health.  Methyl mercury inhibits brain development. PCBs can suppress the immune system and thyroid development and may cause cancer. The contaminants have lead to consumption advisories on many popular fish species, such as walleye, lake trout and salmon.

Meanwhile, fish are lauded as an excellent source of lean protein and omega-3 polyunsaturated fatty acids.  The fatty acids foster neurological development in children and lower the risk of dying from a heart attack.  To maximize health benefits from fish, the American Heart Association recommends eating fish twice a week.

But do the health benefits from Great Lakes fish outweigh the risks from contaminants?

A group of scientists working with the International Joint Commission spent more than a year trying to find out.  They recently reported their findings to the U.S./Canadian group that advises the governments on boundary water issues.

Their answer: We don’t know.

Weighing risks and benefits

The workgroup relied on studies carried out by other researchers. While contaminants in fish have been widely studied, the health benefits of Great Lakes fish remain hazy.  Few researchers have measured omega-3 fatty acids in Great Lakes fish.

“It’s definitely not as clear-cut as I’d hoped in the beginning,” said Bruce Kirschner, an environmental scientist at the commission.

“We know (fatty acids) benefit infants, the growing fetus and they’re good for older adults, but we really don’t know precisely how consuming any species in the Great Lakes would benefit any of these groups,” Kirschner said.  “And then you add in the real complicating factor of contaminants in various concentrations from various areas in the Great Lakes … and it ends up being a really complex situation.”

Risks are real

What researchers do know is that the health risks from eating fish with high concentrations of PCBs, mercury and other contaminants are “very, very real,” said David Carpenter, the director of the Institute of Health and Environment at the University at Albany — State University of New York.  Carpenter is also on the International Joint Commission’s science advisory board.

“Probably the greatest risk is to women of reproductive age because then they’re going to harm their child even before birth by interfering with their brain development,” he said.  “To dumb down your kid for life because the mother ate a lot of contaminated fish before the baby was born — that’s a very serious issue.”

And the evidence that contaminants in fish can harm Great Lakes residents is overwhelming, he said.  Carpenter cited a 1996 study out of Wayne State University in Detroit, Mich.  In that study, researchers followed more than 200 children from the region for 11 years.  They found that children born to women who ate Lake Michigan fish several times a month had IQ scores 6.2 points lower than average.

Health benefits are proven

Not all studies are full of doom and gloom.

According to the Center for Disease Control’s National Health and Nutrition Survey, Great Lakes residents consume about three to four fish meals a month.  But the Ojibwe tribes consume seven to 10 times as much fish as everyone else, said John Dellinger, a professor in the University of Wisconsin-Milwaukee’s college of health sciences.  Dellinger studied Ojibwe fish consumption in the Great Lakes Basin for 12 years.  Their higher fish intake correlates to greater levels of mercury and PCBs in their blood, he said.

Nonetheless, Dellinger’s studies show the Ojibwe are better off for eating all that fish.  “At the levels that they’re eating, with the wide variety of fish they seem to be eating, the effects that we saw actually were positive, not negative,” he said.

Those positive effects included lower rates of diabetes and heart disease, according to the study.

With all the health concerns the tribes contend with, such as diabetes and obesity, telling them to shy away from fish is not a good option, he said.  “Fish are actually a good source of food to be eating, much better than a lot of the other food we eat.  You just have to be careful.”

Reaching a decision

The best advice?  Always select the fish with the least contaminants and don’t weigh health benefits against contaminant concentrations, said Milt Clark, a senior health and science adviser for the Environmental Protection Agency’s office serving the Great Lakes region.  That kind of balancing act is “not the wisest thing.”

Until more is known, Great Lakes residents should follow fish consumption advisories and focus on eating smaller fish, he said.  Small fish usually have lower contaminant concentrations.

At least one scientist is confident that the uncertainty can be reconciled.

Donna Mergler, a member of the International Joint Commission’s science advisory board and professor emeritus at the Université du Québec à Montréal, worked on a similar issue in the Amazon Basin.  With her team’s recommendations, Amazon residents dramatically lowered their mercury intake while maintaining their fish consumption.

The challenge, she said, is to identify the contaminants and nutrients in the different fish species.  From there it is a simple matter of pointing people toward the right fish.

“A fish is not a fish is not a fish,” she said.  “Some have a lot of nutrients and few contaminants, but unless we know it’s hard to make decisions.

“Fish is a very healthy food,” she said.  “We need to find ways of eating it.”

Poll: How often do you eat Great Lakes fish?