First, it was tiny plastic beads from facial washes and toothpaste turning up in the Great Lakes. Scientists now are raising concerns about fibers from synthetic clothing.

Sherri Mason, a chemist with the State University of New York at Fredonia, says Friday that polyester fleeces and similar garments can shed thousands of fibers when laundered. They're making their way to wastewater treatment plants and then into the lakes.

She and colleagues have collected the fibers along with plastic beads and other debris when dragging nets across the lake surfaces in recent years. A 2013 expedition on southern Lake Michigan yielded an unusually high number of fibers.

Fish sometimes eat tiny plastics. Mason says fibers are getting stuck inside their bodies more than other microplastics are.