Fish consumption advisories usually focus on one chemical at a time – like mercury – and these advisories tell you how much of each kind of fish you should eat, and what to avoid. But they don’t often tell you much about mixtures of different chemicals in the environment that could be in fish.
Ken Drouillard is a professor at the Great Lakes Institute for Environmental Research at the University of Windsor. He’s an author of a new study that looks at chemical mixtures and fish advisories.
“Generally, the fish consumption advice tries to put in the state of the art in terms of what we know about the toxicology of these contaminants and how to best reduce health impacts through the consumption of sport fish. The approach that we took in this paper was to say, what if all of the different chemicals themselves were considered a mixture, and what would be the total number of meals if we assumed that each of those chemicals was contributing to an adaptive toxicity?” he says.
Fish advisories tell you how many meals of each kind of fish you can safely eat each week.
The team found that about half of the fish consumption advisories they studied in the Canadian waters of four of the Great Lakes are "potentially not adequately protective."
Drouillard says when they used the multiple chemical method in their study, about 50% of the advisories would need to recommend eating one fewer fish meal.
So should local governments consider changing how they do fish advisories?
Drouillard says it's complicated.
"One of the real challenges is trying to address risk-benefits of eating fish. And of course fish advisories all focus on the risks, but at the same time, we don't want to give the impression to the general public to completely avoid eating fish, because there are a lot of health benefits that accrue from that," he says.
He says generally speaking, fish in the Great Lakes region like yellow perch, sunfish, and white crappie have the fewest contaminants. Moderately contaminated fish include largemouth and smallmouth bass. He says fish like carp and channel catfish are more heavily contaminated (and to some extent, walleye).
Drouillard says officials should make fish consumption information more accessible: like posting advisories on signs in popular fishing spots.
"We see in some cases, for example, in Great Lakes Areas of Concern, we have Michigan and we have Ontario that are posting signs of allowable meals that local shoreline fishers, for example, they can see those advisories posted right in the same areas that they’re fishing," he says.
Drouillard says their research suggests some advisories could stand to be more conservative.
“But I also think it probably takes a little more research to validate whether our approach versus the single-contaminant approach is the most effective and protective measure,” he says.