Shocking Microplastic Pollution Floods Lake Ontario from Toronto's Don River

According to a study published on 2025-10-23, researchers have discovered that the Don River in Toronto, Canada, is flushing an alarming amount of microplastics into Lake Ontario each year. The peer-reviewed study estimates the river basin discharges approximately 500 billion microplastic particles, weighing around 36,000 kilograms, into the lake annually. This is far more than the 160 kilograms of larger plastic items found in the river.

The lead author, Chelsea Rochman, an expert on plastic pollution from the University of Toronto, expressed shock at the high levels of microplastics, stating they are "more on par with places that don't have as good of waste management." Microplastics, tiny fragments no bigger than a pencil eraser, have become ubiquitous and have been found in human blood and Arctic sea ice.

The study identified several common sources of microplastics in the Don River, including construction foam, car tires, plastic pellets, and pieces shed from single-use plastics. The researchers also found that wet wipes and plastic bags are the most common larger plastic items in the river, with tens of thousands of wipes estimated to be present at any given time.

Experts say addressing this pollution will require a multi-pronged approach, including working with companies to prevent construction materials from blowing away, supporting sewer infrastructure upgrades, and potentially banning certain single-use plastics. The city of Toronto is currently in the midst of a $3-billion program to upgrade its aging combined sewer system, which can release untreated sewage and plastic waste into the river and lake during heavy rains.

The researchers suggest that if all plastic pollution was stopped, the Don River may naturally "clean itself" over time. Rochman emphasizes the importance of continued monitoring to understand and address the sources of this microplastic crisis.