Smaller than the eraser on the end of a pencil, microplastics are present in all five Great Lakes. The International Joint Commission’s (IJC) Great Lakes Science Advisory Board’s (SAB) latest report recommends a basinwide effort to monitor microplastic pollution.
The report recommends implementing routine monitoring for microplastics, supported by the standard operating procedures for sampling proposed in the report. The report also proposes a risk-assessment framework, which can use monitoring data to signal when pollution management actions may be needed.
“Plastic is a part of modern life... [and] its inherent durability prevents them from breaking down fully,” said report co-author and Science Advisory Board-Research Coordination Committee Canadian co-chair Rebecca Rooney during the board’s February webinar about the report.
“Coupled with rising production and improper disposal methods [leads] to substantial accumulation in the environment, and the Great Lakes are no exception” said Rooney, also assistant professor at the University of Waterloo.
To better understand the presence of microplastics in the Great Lakes, the IJC’s SAB examined the state of science on microplastics in the Great Lakes, and proposed tools to better monitor and assess plastic pollution.
Hundreds of interested participants joined the board’s February webinar to learn more about the board’s report and advice to Canadian and US governments. The report’s key findings and recommendations are also summarized in an infographic.
The Great Lakes Science Advisory Board’s February 2025 webinar about their Great Lakes microplastics report.
The report identifies some barriers to effectively monitoring the Great Lakes for microplastics. Current efforts are largely project-based, and do not have standardized methods. Furthermore, when the SAB examined all the existing published literature about Great Lakes microplastics “it became clear that there is no widely accepted, shared definition for microplastics,” said report co-author and University of Toronto professor Chelsea Rochman. The SAB proposes defining microplastics by size, including plastics between 1 micron and 5 mm (0.2 inch) in diameter, which is generally consistent with other definitions.
Adopting a common definition for microplastics will make it easier to compare data across multiple studies. “The data in reports and studies of microplastics [were] comparing apples to oranges. With a common definition, comparing apples-to-apples, reduces existing challenges to effective monitoring, risk assessment and management,” said Rochman.
Without systematic, coordinated and regular monitoring of microplastics in the Great Lakes, it is not possible to determine if the level of plastic pollution in the water, sediment, or living organisms is currently “good” or “bad,” or whether the situation is getting better, or worse, over time.
The board proposes tools to support a common and routine approach to monitoring. Included are standard operating procedures (SOPs) for sampling in surface waters, rivers, sediment and aquatic life like plants and fish. This project benefited significantly from the expertise of the Chesapeake Bay Plastic Pollution Action Team, the Southern California Coastal Water Research Project (SCCWRP) and the California State Water Resources Control Board.
To align with similar efforts across North America, the board adapted an existing microplastic pollution risk-based management framework recently developed by SCCWRP.
“Our proposed framework includes three tiers, categorizing ecosystem health as ‘Good,’ ‘Fair,’ and ‘Poor’ based on increasing microplastic concentrations,” said Eden Hataley, report co-author and PhD candidate at the University of Toronto.
The board’s adapted framework tracks ecosystem health trends over time and defines two threshold values of concern. “This categorization is designed to follow the assessment structure of the [Canadian and US] governments’ indicator assessment and reporting that they already use in their State of the Great Lakes reports,” said Hataley. The two thresholds, derived from data on Great Lakes species’ sensitivity to microplastics pollution, represent when microplastics would negatively affect 5 percent and 30 percent of an aquatic species in a community.
The board also adopted SOPs originally developed by SCCWRP and created Great Lakes specific addenda for each. Adopting these SOPs would not only standardize monitoring across the Great Lakes basin, but would align with efforts elsewhere in North America, including Chesapeake Bay and California.
Because of the lack of coordinated, systematic monitoring of microplastics, “it’s not currently possible to establish the status and trends of microplastics in water and sediment and their impacts on the Great Lakes ecosystem” said report co-author and Science Advisory Board-Science Priority Committee member Karen Kidd.
“Without indicators, it’s not feasible to evaluate the effectiveness of efforts to clean up and prevent microplastics pollution. As the saying goes, ‘You can’t manage what you don’t measure,’” said Kidd, also a professor at McMaster University.
To support coordinated monitoring efforts, the board recommends that the United States and Canada assess the status of microplastics in the Great Lakes under the Great Lakes Water Quality Agreement. Specifically, microplastics should be adopted as a Chemical of Mutual Concern (CMC) and monitored as a subindicator for the presence of toxic chemicals in the Great Lakes environment.
Assessing microplastics under the Agreement would commit the United States and Canada to actions to reduce and mitigate microplastic pollution and to report on the status of microplastics in their State of the Great Lakes (SOGL) report, published every three years.
Canada and the United States are currently considering a nomination to designate microplastics as a CMC under the Agreement. If designated, the governments would develop plans to prevent and mitigate microplastic pollution in the Great Lakes. In addition, the governments would assess the status of microplastics in SOGL reporting, to help evaluate if the governments’ actions are effectively improving the Great Lakes environment. The tools proposed in this report can be adapted by the governments to support this work.
The public can help prevent microplastics from entering the Great Lakes, like installing a microplastics filter on their washing machines. “We tested washing machine filters, and they remove about 80% or upwards of the microplastics that come from those machines from our garments. These only work to a certain particle size range, but they’re quite effective,” said Rochman, referring to her work at the University of Toronto.
When available, more information about the nomination of microplastics as a CMC are made available by the Canadian and US governments on their website about their activities under the Great Lakes Water Quality Agreement at binational.net.
Rachel Wyatt is the communications officer at the IJC’s Great Lakes Regional Office.
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