Plastic waste decomposing at sea

Reporting here today at the 238th National Meeting of the American Chemical Society (ACS), the researchers termed the discovery "surprising." Scientists always believed that plastics in the oceans were unsightly, but a hazard only to marine animals that eat or become ensnared in plastic objects.

"Plastics in daily use are generally assumed to be quite stable," said study lead researcher Katsuhiko Saido. "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."

He said that polystyrene begins to decompose within one year, releasing components that are detectable in the parts-per-million range. Those chemicals also decompose in the open water and inside marine life.

Each year as much as 150,000 tons of plastic debris wash up on the shores of Japan alone, Saido said. Vast expanses of plastic waste are now floating on the surface of the world's oceans. The so-called Great Pacific Garbage Patch between California and Hawaii is twice the size of Texas.

Saido, a chemist with the College of Pharmacy, Nihon University, Chiba, Japan, said his team found that when plastic decomposes it releases toxic bisphenol A (BPA) and PS oligomer into the water. Plastics usually don't break down significantly within an animal's body after being eaten. However, the toxic substances released when plastic decomposes in water are in fact absorbed by animals and plants. BPA and PS oligomer are sources of especial concern because they disrupt hormone function and can seriously affect reproductive systems.