In the first study to look at what happens over the years to the billions of pounds of plastic waste floating in the world’s oceans, scientists are reporting that plastics — reputed to be virtually indestructible — decompose with surprising speed and release potentially toxic substances into the water. Scientists always believed that plastics in the oceans were unsightly, but a hazard mainly 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, Ph.D. “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. However, the volume of plastics in the ocean is increasing, so that decomposition products remain a potential problem.
Saido, a chemist with the College of Pharmacy, Nihon University, Chiba, Japan, said his team found that when plastic decomposes it releases potentially toxic bisphenol A (BPA) and PS oligomer into the water, causing additional pollution. Plastics usually do not break down in an animal’s body after being eaten. However, the substances released from decomposing plastic are absorbed and could have adverse effects. BPA and PS oligomer are sources of concern because they can disrupt the functioning of hormones in animals and can seriously affect reproductive systems.
Some studies suggest that low-level exposure to BPA released from certain plastic containers and the linings of cans may have adverse health effects.
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