An estimated 22 million pounds of plastic garbage enters the Great Lakes every year.

The Toronto skyline. Photo: Shutterstock

A recent study from the Rochester Institute of Technology has estimated that around 10,000 metric tons (22 million pounds) of plastic enters the Great Lakes each year. It is the first study to take several smaller, local studies and use mathematical models to extrapolate how much plastic is entering the lake system overall. By comparison, an estimated 40,000 to 110,000 metric tons of plastic enters the oceans from the United States’ coastlines.

Plastics in the Great Lakes either sink to the bottom if they’re heavy enough, or are pushed to the shores of the lakes, whereas in the ocean the plastics group together into “garbage patches” and float on the surface. These plastics account for about 80 percent of the litter that accumulate on the shores of the Great Lakes.

Much of this comes from major population centers like Chicago, Toronto, Cleveland, Milwaukee, or Detroit, all of which introduce more plastic into the Lakes than collects on their shores.

Using hydrodynamic modeling, the researchers were able to see that plastic from Milwaukee or Chicago, for example, ends up on the eastern shores of Lake Michigan, while trash from Detroit or Cleveland heads for the southern coast of Lake Erie, and from Toronto, trash makes its way to southern Lake Ontario.

This new research is certainly saddening, and it will likely come as a big surprise to many people, but it will also help us to better understand how the Great Lakes are affected by pollution.

By applying this research in future projects, we can better understand how pollution like plastics enters into the Great Lakes system, how it moves through the lakes, and how that differs from other bodies and systems of water. This can help us to better understand how to clean that pollution up and, most importantly, prevent it from entering the water in the first place.