A new study co-authored by researchers at the University of Toronto and the Ontario Ministry of the Environment, Conservation and Parks recently found high levels of microplastics in Toronto-caught fish, highlighting the need for large-scale geographic monitoring.

The study discovered that fish caught along Toronto's waterfront have up to 12 times more microplastics per serving than some store-bought alternatives, although researchers are still trying to determine the long-term effects of microplastics on human health. 

While plastic debris comes in all shapes and sizes, those that are less than five millimetres in length (roughly the size of a pencil eraser) are referred to as "microplastics." 

They can come from a wide range of sources, including larger plastic debris that breaks down into smaller pieces, which can pass through water filtration systems and end up in oceans and lakes. 

The study's researchers observed a total of 45 fish caught in Humber Bay along Toronto's waterfront. They found that each fish's fillet, on, average, contained 56 particles of microplastics. 

Assuming that humans eat fish twice a week, that's 12,800 particles per year or 123 microplastics per serving, which is over 12 times as many particles as the nine microplastics ingested per serving of grocery store Alaska Pollock found in a study by the same authors published earlier this year. 

Usually, when trying to examine how many microplastics are present, researchers only look at the content of the gut, but this recent study's researchers also assessed the fillets of the freshwater fish that they monitored, which are usually what humans consume. 

The study also notes other recent studies, which have documented the presence of microplastics in breast milk, placenta, three lungs, and human blood. 

Researchers also highlight other laboratory experiments using fish that have found that microplastics can cause stress to the immune system, impact growth, contribute to changes in behaviour, and even deformities during development. 

While the study emphasizes that its findings may represent the worst-case scenario, researchers also offer many solutions to prevent further contamination. 

These include more monitoring and risk assessment to build a more comprehensive picture of plastic pollution in Ontario's waters and an understanding of the impact on human health, more research on the ground, such as the research on lakes currently underway at IISD Experimental Lakes Area, and prevention strategies to reduce plastic pollution.