U.S. and Canada together discard 22 million pounds of plastic into the waters of the Great Lakes each year, according to a new Rochester Institute of Technology (RIT) study. Most of it washes up along the shores, accounting for 80 percent of the litter found there.

Researchers said that Chicago, Toronto, Cleveland and Detroit are the worst contributors to the plastic pollution. Half of the plastic dumped into the Great Lakes—11 million pounds—goes into Lake Michigan. Lake Erie comes in at number two, receiving 5.5 million pounds. Lake Ontario gets 3 million pounds of plastic waste a year, with Lake Huron and Lake Superior receiving smaller amounts.

"This study is the first picture of the true scale of plastic pollution in the Great Lakes," said Matthew Hoffman, assistant professor in RIT's School of Mathematical Sciences and lead author of the study.

Plastic pollution in Lake Michigan is approximately the equivalent of 100 Olympic-sized pools full of plastic bottles dumped into the lake every year.

"Every piece of plastic entering our watersheds is an example of a serious design flaw: we are manufacturing products that have no recovery plan or value after they leave consumer's hands," said Anna Cummins, co-founder and global strategy director of 5 Gyres Institute. "Just as we demand that people dispose of their trash properly, we must also demand that companies take responsibility for the end life of their products."

Plastic debris in the Great Lakes moves differently than in the ocean. Instead of the free-floating garbage patches that are driven by ocean currents, like the Great Pacific Garbage Patch, plastic in the Great Lakes is carried by winds and currents toward shore.

"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 explained. "Particles released from Toronto appear to accumulate on the southern coast of Lake Ontario, including around Rochester and Sodus Bay."

But, like the oceans, much of what remains as floating trash in the Great Lakes consists of microplastics, which are consumed by fish and enter the food chain.

"Similar to what we find worldwide, much of the plastic is microplastic, which are fragments smaller than a grain of rice and practically impossible to clean up, making prevention the only real option," said Marcus Eriksen, research director at 5 Gyres Institute.



Estimates of surface microplastics entering the lakes each year show 9,722 pounds in Lake Erie, 3,174 pounds in Lake Huron and less than 50 pounds in Lake Superior.

"Like our successful microbead campaign, the fact of so much trash entering the Great Lakes is an opportunity to identify the most common brands and work with those companies to improve recovery or choose something less harmful than plastic for their products and packaging," said Eriksen.



The RIT study, which will be published in an upcoming issue of Marine Pollution Bulletin, used computer simulations and mathematical modeling to provide a more complete and accurate picture of plastic pollution in the Great Lakes.

Researchers said that the study could help inform future cleanup and prevention efforts.