By JACK NISSEN
Capital News Service
LANSING — A new study questions whether public health advice on eating Great Lakes fish is restrictive enough.
Ken Drouillard, a professor at the University of Windsor, looked at whether the Great Lakes region recommends sufficient restrictions on monthly meals of sport fish.
The results are in, and while they say no, they weren’t as restrictive as Drouillard expected.
Consumption advisories are used to limit human exposure to harmful substances that fish may contain.
Drouillard found that 60 percent of advisories would provide more restrictive advice under a method that takes into account multiple chemicals in a fish. That’s contrary to the current practice of basing fish advisories on just a single contaminant, according to the study published in the Journal of Environmental Health Perspectives.
Michael Murray, a staff scientist with the Great Lakes Regional Center at the National Wildlife Federation in Ann Arbor, said “Assuming those results are reasonable — and there has been a lot of research on the potential risk to human health from PCBs and mercury exposure through fish consumption — then it makes sense there are a lot of advisories that need to be revisited.”
The decision to use a contaminant-mixture process is based on an assumption that when consuming PCBs and mercury—common contaminants involved in fish advisories— they compound each other’s response in the human body.
While the researchers predicted the number of restrictions would be much higher with the mixture method, they didn’t increase as much as they expected, Drouillard said.
Fish advisories depend on factors like the size of the fish, its species and where it is caught. Recommendations are based on monthly consumption rates, with 31 being not very restrictive and zero being the most restrictive.
Murray said, “They’re typically developed on an individual contaminant basis, so we’ll develop an advisory for just mercury alone, then we’ll look at possible advisories for PCBs by themselves. It’s typical then they’ll base an advisory on whatever is more restrictive.”
The system has been used by the Ontario Ministry of Environment and Climate Change since the 1970s. Drouillard wanted to study its effectiveness.
Instead of looking at what contaminant was most prevalent, he considered a combination of contaminants. While both mercury and PCBs have different origins, they share a similar toxicological response.
“Because particularly the two major compounds, mercury and PCBs, have a similar toxicological endpoint, we might consider treating them as a mixture,” Drouillard said. “But we would certainly say there should be follow up research to basically document whether for example combined exposures to the two contaminants have an additive effect on the toxicity.”
The single-contaminant process is typically used for non-carcinogens because of their different end-responses,
PCBs are byproducts of industrial sources. While the electric coolant and insulator was banned in 1979, it still persists in the environment. The Environmental Protection Agency’s National Coastal Assessment says it’s the most common contaminant in the Great Lakes.
Toxicologist Jennifer Gray of the Michigan Department of Health and Human Services, said mercury comes from natural sources like coal.
Research shows that burning coal is the largest source of mercury emissions in the United States.
Drouillard said .mercury is the number- one driver of advisories in inland lakes in the region.
“Ultimately the reason why we’re worried about exposures to PCBs and mercury by humans, particularly the sensitive population, which is women of childbearing age and children under the age of 15, is because they basically contribute to disorders in the nervous system,” he said.
Revising restrictions is tricky. The concern is to make them sufficient but not scare the public away from eating fish, he said. Thus the study sought to produce more accurate advisories without unnecessarily frightening anyone.
Fish is good source of minerals like iron, zinc and magnesium. They also carry protein, omega 2 and 3 fatty acids, which help keep the heart and brain healthy.
The Great Lakes were chosen for the study due to their chemical complexity, Drouillard said. As former industrial hub, legacy chemicals in the region like PCBs and mercury were common byproducts of industry and continue to accumulate in fish
Jack Nissen writes for Great Lakes Echo.