March 28, 2010
Scientists have discovered that despite being known for their hardness, polycarbonate plastics actually decompose in oceans, leaching chemicals, including BPA, throughout the marine ecosystem.
"We were quite surprised to find that polycarbonate plastic biodegrades in the environment," said Dr. Katsuhiko Saido with Nihon University in Chiba, Japan. "Polycarbonates are very hard plastics, so hard they are used to make screwdriver handles, shatter-proof eyeglass lenses, and other very durable products. This finding challenges the wide public belief that hard plastics remain unchanged in the environment for decades or centuries. Biodegradation, of course, releases BPA to the environment."
Organisms live off of the decomposing epoxy and polyurethane plastic paint used to seal the hull of this ship. Photo by: Katsuhiko Saido.
"When epoxy resin breaks down, it releases BPA, a typical endocrine disruptor," Saido explained. "This new finding clearly demonstrates the instability of epoxy, and shows that BPA emissions from epoxy [plastic paint] do reach the ocean. Recent studies have shown that molluscs, crustaceans and amphibians could be affected by BPA, even in low concentrations."
The researchers analyzed sand and seawater from over 200 sites across 20 countries, focusing on Southeast Asia and North America. All of the results showed what Saido calls "significant" BPA contamination: ranging from 0.01 parts per million to 50 parts per million.
The fact that plastics decompose in the oceans was first recorded last year by Saido and colleagues who showed that light, white-foamed plastic decomposed rapidly in the oceans, releasing toxins. However, this new discovery shows that even some of the world's toughest plastics disintegrate in the marine environment, polluting it.
According to Saido, plastic is the main type of garbage in marine environments. Littering either directly in the ocean or being carried through waterways into the marine environment, plastics have created vast floating garbage islands. One between California and Hawaii is twice as Texas, and aptly known as the Great Pacific Garbage Patch. Another patch was recently announced floating in the Atlantic Ocean in the western Sargasso Sea; its size is unknown.
"Marine debris plastic in the ocean will certainly constitute a new global ocean contamination for long into the future," Saido predicted.
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