Amidst waves and wildlife in the world's oceans, billions of pounds of Styrofoam, water bottles, fishing wire and other plastic products float in endless circles.

This bobbing pollution is more than just an eyesore or a choking hazard for birds. According to a new study, plastic in the oceans can decompose in as little as a year, leaching chemical compounds into the water that may harm the health of animals and possibly even people.

"Most people in the world believe that this plastic is indestructible for a very long time," said Katsuhiko Saido, a chemist at Nihon University in Chiba, Japan. He spoke this week at a meeting of the American Chemical Society in Washington, D.C.

"We are now concerned that plastic pollution is caused by invisible materials," Saido said through an interpreter. "This will have a great effect on marine life."

Patterns in ocean currents create conglomerations of swirling trash that have received a burst of attention recently. The so-called Great Pacific Garbage Patch, for one, is a mound of waste, mostly plastic, that's about twice the size of Texas. It lies some 1,000 miles off the west coast between California and Hawaii.

In Japan, Saido said, up to 150,000 tons of plastic wash on shore each year. Much of it is Styrofoam, a type of polystyrene plastic.

In their lab, Saido and colleagues used a new chemical technique to simulate the decomposition of polystyrene plastic in the oceans at 30 degrees Celsius (86 Fahrenheit). The process produced some potentially toxic chemicals, including bisphenol A (BPA) and PS oligomer.