Nearly 22 million pounds of plastic debris enter the Great Lakes annually from the United States and Canada, according to a recent study by the Rochester Institute of Technology (RIT).
"This study is the first picture of the true scale of plastic pollution in the Great Lakes," said Matthew Hoffman, an assistant professor in mathematics and the lead author of "Inventory and Transport of Plastic Debris in the Laurentian Great Lakes."
Hoffman used computer simulations to follow the volume of plastic debris moving across both state and international boundaries, with nearly half going into Lake Michigan. Lake Erie followed a distant second with 5.5 million pounds, while Lake Ontario had 3 million, Lake Huron 1.3, and Lake Superior the least at about 70,000 pounds.
To put that into perspective, annual pollution in Lake Michigan is the equivalent of 100 Olympic-size pools full of plastic bottles, while that for Ontario equates to about 28.
While bottles and other plastic pollution accumulate in gigantic "garbage patches" in the oceans, winds and currents mostly carry them to shore in the Great Lakes.
"Plastic accounts for approximately 80 percent of the litter on the shorelines of the Great Lakes," RIT said in announcing the report. "The study quantifies dense plastic that quickly sinks and surface plastics like microbeads, fragments and pellets, plastic line, and Styrofoam, which could be consumed by wildlife and potentially enter the food chain."
Estimates of these tiny plastic particles floating or suspended in the lakes range from nearly 10,000 pounds in Erie to 436 pounds in Superior.
"We know some of the plastic sinks. But when we input the numbers, this is the amount that's floating near the surface," Hoffman said, adding that these microplastics are most likely to end up in fish and other aquatic life. "But we also don't know a lot about what happens to the plastic that doesn't float and where it ends up."
Meanwhile, researchers at the University of Wisconsin-Superior warned that these pollutants could pose a serious threat to aquatic ecosystems in 2013. And both the United States and Canada are working toward stopping production and sale of personal care products that contain tiny plastic beads, which wash down drains, pass unfiltered through treatment plants and enter the Great Lakes and other waterways.
Not surprisingly, Hoffman and his team revealed that major population centers are the primary sources of pollution, with Chicago, Toronto, Cleveland, and Detroit releasing more plastics than accumulate on their adjoining shorelines.
"Most of the particles from Chicago and Milwaukee end up accumulating on the eastern shores of Lake Michigan, while the particles from Detroit and Cleveland end up along the southern coast of the eastern basin of Lake Erie," Hoffman said. "Particles released from Toronto appear to accumulate on the southern coast of Lake Ontario, including around Rochester and Sodus Bay."