'Pervasive environmental problem': High levels of microplastics in fish caught in Toronto - Toronto

Fish fillets caught along Toronto’s waterfront contain up to 12 times more microplastics per serving than some common store-bought alternatives, according to a newly published study.

While scientists are still trying to determine whether microplastics pose a direct risk to human health, the study co-authored by researchers at the University of Toronto and the Ontario Ministry of the Environment offers a glimpse into how car tires and other plastics break down into tiny pieces and end up in fish — and on the dinner table.

“The high number of particles observed in fish from Humber Bay highlights the need for large-scale geographic monitoring, particularly near sources of microplastics,” the study said.

Microplastics, no larger than the width of a pencil eraser or a mitochondria, have become ubiquitous, from human blood to Arctic Ocean ice. In fish, these larger, decomposed pieces of plastic are linked to poorer growth and reproduction, among other problems.

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The researchers examined a total of 45 fish captured in Humber Bay, where the Humber River flows into Lake Ontario along Toronto’s waterfront.

The microplastics were found, in varying sizes and concentrations, at an average of 138 particles per fish, according to the study, which is much higher than averages reported in other studies. The same University of Toronto research lab, for example, found an average of 17 particles per fish in Lake Simcoe.

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Madeleine Milne, co-author of the latest study, said the findings show how microplastic pollution has become a “pervasive environmental problem”.

“It’s time for us to start thinking about how we’re going to solve this problem, whether it’s through policies to reduce single-use plastics, thinking about environmental solutions to clean up microplastics and other types of solutions like that,” said Milne, who conducted the study as part of his undergraduate thesis at the University of Toronto, with professor Chelsea Rochman.

Despite the contamination, the study found no evidence that microplastics were accumulating in the fish’s bodies as they aged.

“I think it’s promising. I think we just need to understand why this is happening,” said Milne, who is now a graduate student at the University of Manitoba.

The authors point out that the results likely represent a “worst-case scenario” for freshwater fish contamination. That’s because they looked at both the gut and the fillet of the fish, whereas studies typically only look at the gut, and they caught the fish in a part of the lake known to be highly polluted.

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Milne, who also recently co-authored a study on microplastics in common store-bought foods, says the Humber Bay fish contained about nine to 12 times more microplastics per fillet serving than minimally processed Alaska pollock. The number of particles per gram of Humber Bay fish fillet, about 0.5, was still within the range identified by a systematic review of other studies on microplastics in seafood, the study found.

The fillets pale in comparison to other common forms of human exposure to microplastics, the study notes. The authors estimated that a person who ate two servings of Humber Bay fish fillets per week would ingest about 12,800 particles per year, compared with about 90,000 particles per year from bottled water.

Lindsay Cahill, whose research into whether human exposure to microplastics negatively affects pregnancy is supported by the federal government, called the study released Wednesday a “significant step.”

“We’re starting to get real numbers that allow us to look at our exposure in humans and decide whether our exposure is harmful or not,” said Cahill, an associate professor at Memorial University of Newfoundland.

But, she noted, more research is needed to determine whether, and to what extent, this exposure is actually harmful.

Some studies have raised concerns.

A study published earlier this year in the New England Journal of Medicine, with notable limitations, found more evidence of inflammation in patients with microplastics in their blood vessels. Another 2021 study found that people with inflammatory bowel disease had higher levels of microplastics in their stool than healthy subjects.

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Of the five Great Lakes, Lake Ontario had the highest concentration of microplastics, according to an environmental report released last year by Ontario’s auditor general.

In an emailed statement, a spokesperson for the Ontario Ministry of the Environment, Conservation and Parks said it is studying microplastics in fish to provide “baseline information to help understand the level of concern as risk information becomes available.”