At a recent meeting of the American Chemical Society, the worlds largest professional scientific society, a researcher from Japan presented a paper demonstrating that plastics floating in the ocean break down faster than expected. Previously it was thought that plastics broke down very slowly (hundreds of years) and at very high temperatures.
Normally we like chemicals that break down, that is, degrade into smaller chemicals and eventually (hopefully) into carbon dioxide and water. But the study by Dr. Katsuhiko Saido of Nihon University suggests that when the plastics break down they release contaminants - some of them potentially very toxic.
The problem is more urgent because the oceans are now filled with plastic, which the New York Times called in a recent editorial, "...an amorphous, floating mass of waste plastic trapped in a gyre of currents..." Dr. Saido reports that these floating masses of plastic are releasing similar contaminants in seawater samples collected near Malaysia and the Pacific Northwest in addition to the northern Pacific between Hawaii and Japan. The northern Pacific patch is estimated to be on the order of twice the size of the state of Texas and may contain as much as 100 million tons of plastic debris.
Since plastic waste has long been known to trap up to a million seabirds every year and some 100,000 marine mammals, the discovery that degradation of the plastic releases contaminants is an added concern.
A video of the north Pacific gyre and plastic can be seen here.
[Note: Photograph by René Ehrhardt: attribution license]