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Styrofoam degrades in seawater

Study suggests besides the visible plastic, smaller bits also foul the waters

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6:11pm, August 20, 2009
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WASHINGTON — From the beer cooler at the bow to flotation devices and bumpers, life on the sea often involves light, white foamed plastic, commonly known by the trademark Styrofoam. But life in the sea is encountering the plastic as well. The chemical building blocks of foamed polystyrene have been detected in several areas of the Pacific Ocean and lab experiments demonstrate that the plastic degrades at seawater temperatures, researchers reported August 19 at a meeting of the American Chemical Society.

“Plastics are a contaminant that goes beyond the visual,” says Bill Henry of the Long Marine Laboratory at the University of California, Santa Cruz. The researchers’ reports are important, he says, because they provide “some of the first evidence of polystyrene as a potential contaminant to wildlife that’s more on the molecular level.”

Polystyrene foam is a manufactured plastic primarily made up of rings of carbon and hydrogen, called phenyl groups, attached to long hydrocarbon chains that can break into smaller styrene units. Studies suggest that the smallest of these units — the styrene monomer — is carcinogenic in mice, but its effect on other organisms isn’t yet clear.

Water samples collected off Malaysia and the U.S. Pacific coast and in the northern Pacific Ocean all contained styrene monomers, as well as styrene dimers and trimers, reported Katsuhiko Saido of Nihon University in Chiba, Japan. Saido and his colleagues also degraded polystyrene foam in the lab at 30º Celsius, similar to seawater temperature in some areas. The team found that the various smaller styrene units were present in the same relative quantities Katsuhiko Saido of Nihon University in Chiba, Japan in both the lab and in the water samples.

Much of the research on plastic pollution in the oceans has focused on what can be seen with the naked eye, says Joel Baker of the University of Washington Tacoma. Studies on animals tend to investigate damage from plastic nets or ingestion of visible chunks. But this new work adds to a growing body of evidence that many kinds of plastics break down in seawater into pieces too small to see.

“We are concerned that plastic pollution is also caused by these invisible materials and that it will harm marine life,” Saido said.

While the potential toxicity of these tiny plastic constituents is understudied for much of marine life, plastics are abundant in many forms. Marine litter is now 60 to 80 percent plastic, reaching 95 percent in some areas, according to a review by Charles Moore of the Algalita Marine Research Foundation in Long Beach, Calif., published in October 2008 in Environmental Research. And plastics, including polystyrene, are common in the wads of accumulated undigested matter that young black-footed albatrosses cough up before they fledge, Henry says.

Getting at the effects on marine life is challenging—plastics travel long distances, their distribution in the oceans isn’t uniform and scientists are still refining methods to detect and analyze the materials. But, Baker says, “almost all of the plastic that enters the ocean stays in the ocean.”

Though plastics have benefits, Baker says, there’s a lot of gratuitous use. “Now is a ripe opportunity to be more judicious with how and when we use plastics to avoid this loading of the ocean,” he says.

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