SAN FRANCISCO, July 8 (Xinhua) -- A University of Washington (UW) undergraduate has discovered a problem much closer to home: nearly invisible bits of plastic on Puget Sound beaches, along the northwestern coast of the U.S. state of Washington.

As a year-long project toward a UW bachelor's degree, Frances Eshom-Arzadon visited 12 beaches around Puget Sound to tally the number of microplastics, generally classified as fragments between 0.3 and 5 millimeters, or 1/100 to 1/5 of an inch, or smaller than a grain of rice.

As part of her senior thesis project, the oceanography major, who graduated in June, visited each location once at the same time along the Seattle and Everett shorelines in the tidal cycle between November and February, scraped sediment from an area just below the wrack line, the line of debris left by the high tide.

Back in the lab, Eshom-Arzadon dried the samples, then used chemicals and weight-based techniques to separate the plastic from sand and other material.

Her results show that small plastics are widespread along the shore of Puget Sound. All 12 samples contained microplastics, at an average of 1,776 pieces per 3-foot-square, or nearly 0.28-square-meter, sampling plot.

The highest concentration of plastics by number was at Howarth Park in Everett, followed by Carkeek Park and Alki Beach Park in Seattle.

The cleanest beaches, according to a recent posting on the university's website, were found to be at Mukilteo Lighthouse Park and Edmonds Marina Beach, both situated on points of land near ferry terminals.

Eshom-Arzadon became interested in this topic after doing an undergraduate service learning project with the UW-based Coastal Observation and Seabird Survey Team, or COASST. She volunteered to survey beaches around Seattle and her native Edmonds looking for stranded birds and marine debris. She also took an undergraduate class on marine pollution that included a section on marine plastics.

"Plastics can harm marine life, and can in some cases be the primary cause of death," she was quoted as saying in the posting. "Smaller organisms ingest microplastics, and then larger organisms, including humans, consume it indirectly."

Her sampling methods followed the procedures established by Julie Masura, a UW Tacoma lecturer who has been tracking marine microplastics in the region for almost a decade. "Plastics, specifically microplastics, have been found in over 90 percent of the surface samples collected in Puget Sound since 2008," said Masura. "We have yet to correlate the presence of plastic and other environmental factors."

Eshom-Arzadon's project included counting the plastic fragments and classifying them into six types: Styrofoam, fibers, fragments, flakes, films and synthetic sponges. Some 73 percent of the pieces she collected on local beaches were microfibers.

These thin strands are not from the breakdown of larger litter, such as plastic bottles or disposable cutlery; rather, they start when fabrics shed fibers that flow out with laundry water after washing synthetic fabrics, like polar fleece or other types of polyester.

"I wasn't expecting to find so many fibers," Eshom-Arzadon said. "When people do laundry, all their effluent with those microfibers is getting washed out. Those fibers come off clothes and get washed out already in the size of microplastics, so they can't be filtered out."

She noted that front-loading machines have been shown to generate fewer microfibers in washing water, while some clothing companies have begun efforts to produce synthetic fabrics that shed less fuzz.