Hardly indestructible, plastics begin decomposing in ocean within a year, spreading harmful chemicals

Jeremy Hance
August 20, 2009

Scientists had assumed that plastics were basically indestructible. While floating plastic in the ocean was dangerous to particular species of marine life which consumed them or got snared by them, the scientists thought that the threat didn’t extend beyond this. However, a new study shows that plastic in the ocean may be quite insidious. Researchers found that so-called indestructible plastics actually decompose in the ocean, releasing potentially toxic substances throughout the seas.

"Plastics in daily use are generally assumed to be quite stable," said study lead researcher Katsuhiko Saido, Ph.D. a chemist with the College of Pharmacy, Nihon University, Chiba, Japan. "We found that plastic in the ocean actually decomposes as it is exposed to the rain and sun and other environmental conditions, giving rise to yet another source of global contamination that will continue into the future."

A boy in Japan points out Styrofoam debris from the ocean. Photo by: Katsuhiko Saido.
It can take only a year for polystyrene, one of the most common plastic types, to begin decomposing. Its leaked chemicals may decompose in open water or inside marine life.

Plastic pollution is ubiquitous throughout the oceans. Saido, who is from Japan, said that 150,000 tons of plastic debris washes up on Japanese shores alone every year. Floating islands of plastic commonly form in the open ocean. One of these islands, floating between California and Hawaii, is twice the size of Texas.

The chemicals which are released into the water by decomposing plastics include bisphenol A (BPA) and PS oligomer. These chemicals have been shown to disrupt hormone functioning in animals and affect reproductive processes. Three other chemicals were found in the lab when the plastic was broken down: styrene monomer (SM), styrene dimmer (SD), and Styrene trimer (ST). SM is already a proven carcinogen, while both SD and ST may also cause cancer.

The study raises questions as to whether plastics also break down in fresh water.

The findings were announced this week at the 238th National Meeting of the American Chemical Society (ACS) in Washington, D.C.

In Japanese

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Jeremy Hance
mongabay.com (August 20, 2009).

Hardly indestructible, plastics begin decomposing in ocean within a year, spreading harmful chemicals.