TRAVERSE CITY, Mich.—An organization representing more than 100 cities in the U.S. and Canada asked federal and industry officials Tuesday for action on the recently discovered problem of "microplastic" pollution in the Great Lakes.

Over the past two years, scientists have reported finding thousands of plastic bits—some visible only under a microscope—in the lakes that make up nearly one-fifth of the world's fresh surface water. Large masses of floating plastics also have been detected in the world's oceans.

Scientists believe some are abrasive "microbeads" used in personal care products such as facial and body washes, deodorants and toothpaste. They're so minuscule that they flow through screens at waste treatment plants and wind up in the lakes, where fish and aquatic birds might eat them, mistaking them for fish eggs. They also could absorb toxins.

"Even though you cannot see them, they pose a very real threat to human and wildlife health," said John Dickert, mayor of Racine, Wis., and secretary-treasurer of the Great Lakes and St. Lawrence Cities Initiative.

The group sent letters to the U.S. Environmental Protection Agency and its counterpart, Environment Canada, asking what they plan to do about the problem. David Ullrich, the organization's executive director, acknowledged it could take years to develop a regulatory crackdown on microplastics.

In the meantime, his group is sending letters to 11 companies that use microplastics, asking them to switch to biodegradable alternatives. Some are doing so. Procter & Gamble and Johnson & Johnson have said they'll phase out microbeads, and L'Oreal says it won't develop new products that include them.

"We think it makes more sense to appeal directly to the people involved and say, 'Let's work together and try to solve the problem; let's do the right thing,'" Ullrich said.

Additionally, the group is encouraging mayors in the eight states and two Canadian provinces adjoining the lakes to urge residents to buy products without microbeads. "We're not calling for a boycott, but we're asking citizens to inform themselves," Ullrich said.

Scientists led by chemist Sherri Mason of State University of New York at Fredonia and the 5 Gyres Institute, a nonprofit group based in California, took samples from all five Great Lakes in 2012 and again this year by skimming the surfaces with trawl nets attached to vessels.

In a paper published online by Marine Pollution Bulletin, they reported finding the plastic bits in Lakes Erie, Huron and Superior, with the highest concentrations in Erie. Mason said samples taken this summer from Lakes Michigan and Ontario are still being analyzed, but initial inspections turned up microplastics from both.

Pressuring companies to phase out microplastics quickly in favor of biodegradable abrasives such as grape and apricot seeds is the best way to deal with the problem, Mason said. Because of their size and wide distribution, there's no practical way to remove the particles from the lakes.

"Unfortunately, once they get into the water, they get widely distributed," she said. "You can't just go out and filter all the water."

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