There are rafts of junk plastic in the oceans, some of them the size of a large country (e.g. Turkey), and scientists have been worried about them for many years. A recent study by a team from Nihon University (Chiba, Japan) has put new facts to those fears: The hard plastic containers constructed of polycarbonate, once thought to be non-degrading, are degrading and producing the endocrine disruptor bisphenol A (BPA). These containers make up a significant proportion of the ocean-floating plastic. Adding to the oceanic levels of BPA are the epoxy paints used to coat the hulls of many ships. Together these two sources have raised BPA concentrations in parts of the oceans to levels that may have negative biological effects.
This same research team announced in August of 2009 that polystyrene plastic, the material used to make styrofoam plastics, is a source of ocean-born toxins. The researchers analyzed samples from beach sand and seawater from 200 sites in 20 countries, mostly in North America and the Pacific Basin. They found BPA concentrations ranging from 0.01 parts per million (ppm) to 50 ppm. Other studies have shown that even low concentrations are having an effect on sea life. The plastics industry, in general, continues to contend that BPA, although present in many things (water, people, plants), is not found at toxic levels.
Katsuhido Saido, professor at Nihon University School of Pharmacy and lead researcher of the study also notes that the epoxy paints used to protect the hulls of sea-going vessels also degrade and produce BPA.
Saido said that waste plastics are finding their way into the environment through littering, and also may be carried by water into the oceans, spreading this pollution widely. Each year as much as 150,000 tons of plastic debris wash up on the shores of Japan alone, Saido said. Vast expanses of waste, consisting mainly of plastic, float elsewhere in the oceans. The so-called Great Pacific Garbage Patch between California and Hawaii was twice the size of Texas and mainly plastic waste. Plastics are, in fact, the main source of garbage in marine debris, according to Saido. “This process is expedited by the low temperatures at which plastic degradation can occur, temperatures present in oceans,” he added.
“Marine debris plastic in the ocean will certainly constitute a new global ocean contamination for long into the future,” Saido predicted.
The toxicity of the oceanic plastic rafts will be a matter for research and debate for some time. It is difficult to trace the effects of BPA to specific biological problems in specific species. Most scientific studies, so far, tend to extrapolate what compounds with the chemical characteristics of BPA could do to the endocrine or other systems. Worldwide, government agencies have been pronouncing on the effects and prohibitions for BPA – some are fairly strict, others permissive.
From an intuitive point of view, country sized rafts of plastic junk fit with the image of growing ‘dead spots’ in the oceans and other pollution related problems. As with so many other intuitive environmental insights, the hard data from research is either skimpy or subject to multiple interpretations.