Researcher wants answers about toxins in northern Ontario fish

An environmental scientist in Sudbury is trying to figure out why contaminants are showing up in some northern Ontario fish. 

Gretchen Lescord, an environmental scientist and post-doctoral fellow at Laurentian University in Sudbury, co-published a paper that suggests while mercury in northern fish is still the biggest concern, levels of chromium and arsenic concentrations are also raising eyebrows. 

"The concentrations are still relatively low, but we still need to understand better why and how they're being accumulated in fish," she said. 

Most concerning is the presence of hexavalent chromium, a problematic carcinogen, Lescord said. 

"The issue is it's quite hard to measure those individually in fish or even in water," she said. "It is pretty challenging to do."

It was Lescord's studies into mercury contamination in fish, as well as information sessions with remote communities, that led her to look into other elements that were appearing in fish, like chromium and arsenic.

"Mercury is by far sort of the most concerning contaminants in Ontario fish because it's so pervasive and widespread," Lescord said. 

"What happens is mercury gets released into the atmosphere from some distant anthropogenic sources — things like coal and fire burning are a big source of mercury — and they can be carried long distances in the atmosphere and then get deposited on landscapes."

Contaminants enter food chain

Those deposits can make it as far as remote northern Ontario, Lescord said. From there, the contaminants infect the food chain.

"In general what we see is that big fish that feed on other — predators —  they tend to have higher mercury concentrations when compared to a smaller fish or a fish that feeds on the zoo plankton," she said.    

"So if you caught a really big walleye, for example, it's probably going to have higher mercury concentrations than if you caught a small whitefish." 

The goal of her research, is to find out why some fish end up with higher levels than others.

That, in turn, could help people when they research what fish they're eating.

The province currently provides information on recommended servings of fish, depending on what lake they're pulled from, or the fish's size.

Lescord said she hopes her research can answer why certain fish have more contaminants than others, and what factors influence the levels of toxins.