On average, the researchers found 138 microplastic particles in fish taken from Lake Ontario at Humber Bay — one contained 1,300 pieces of rubber.
The Star By Patty Winsa – A new study by University of Toronto researchers and the provincial environment ministry reveals that more than a hundred microplastic particles can be routinely found in freshwater fish from Humber Bay in Lake Ontario.
Tiny pieces of plastic have previously been found in lake fish, but the new study, published Wednesday, is the first to find them in such high numbers. It reports an average of 138 particles per fish, compared to past studies, which found an average of eight.
The research also found microplastics in the fish’s fillets — although not as many as found in the gut — a fact that’s “concerning as this is what humans eat and there is no clear understanding of the impacts that ingested microplastics might have on humans,” said lead study author Madeleine Milne.
“Further, it’s not fully understood how these microplastics in the fillets could harm fish, potentially contributing to issues surrounding quantity and quality of recreationally caught fish.”
Fish have long been known to absorb toxic chemicals from the water and food they eat, and the ministry already publishes a table with recommendations for the maximum consumption of fish per month based on the type and location of the catch in Ontario.
However, less research has been done on the harmful effects of microplastics, fragments that are five millimeters or less and contain many toxic chemicals and additives. Because of that, Milne said, it has been “more challenging to understand what kind of effects they might have” on humans.
In fish, research has shown the particles in their gastrointestinal tract and stomach can block their digestive systems and interfere with their ability to feed.
The study, which sampled 45 fish from six different species found in Humber Bay, found that on average there were 93 plastic particles in the gastrointestinal tracts of the fish and another 56 particles in the fillets.
But one fish contained 1,300 rubber pieces, most likely from tires, said Milne. An earlier study by the Rochman Lab at U of T found tire particles are one major source of microplastic pollution in the city, along with litter and artificial turf.
The pieces are generated from the wearing down of tires while driving, and the rubber accumulates on the road where it is washed into rivers and lakes in heavy rain or snow melts, Milne explained.
Milne did the research while working on her undergraduate degree in ecology and evolutionary biology at the University of Toronto. She is now completing a Master’s at the University of Manitoba.
The research was commissioned by the provincial Ministry of the Environment, Conservation and Parks, said Milne, and could lead to new recommendations for the safe consumption of fish from the Great Lakes.
Most of the lab research was conducted during the pandemic in 2021. The fish were dissected toobtain the gut and the fillet. Chemicals were used to degrade the tissue itself, but leave behind the microplastics, which were analyzed to determine the type of plastic.
The mechanism for how the plastic particles end up in the fillets is not fully understood yet, she said.
The study, published Wednesday in the peer-reviewed journal Environmental Health Perspectives, highlights not only that microplastics can be found in high numbers in fish, but a need to stop the fragments from washing into rivers and lakes in the first place.
The sediment and water in Humber Bay, where the fish were caught, is contaminated, according to the study, because of its proximity to Toronto.
Milne said large-scale solutions, such as the reduction of single-use plastics and recycling, will help, but there’s also a need for more downstream solutions, like the Rochman Lab’s seabins project at Toronto Harbour.
The bins, like giant floating vacuums, can suck out hundreds of plastic pieces from the water in a day.