Monday, July 12, 2010
From The Japan Times:
Umbrella handles. Pens. Popsicle sticks. Lots and lots of toothbrushes. These are just a few of the items that make up the approximately 13 million sq. km Eastern Garbage Patch, an immense plastic soup in the Pacific Ocean that starts about 800 km off the coast of California and extends westward. Sucked from the coasts of Asia and America by ocean currents, or discarded at sea, plastic debris accumulates there in an ever-growing mass that does not biodegrade and is said to be already larger than the United States.
Scientists have long known that plastic in the garbage patch and elsewhere is stuffing the stomachs of seabirds and causing them to starve, suffocating fish and choking marine turtles.
But what is now becoming clear is that when pieces of plastic meet other pollutants in the ocean, the results can be even more toxic. That's because, as a growing number of studies are showing, the plastic debris absorbs harmful chemicals from the seawater it floats in, acting like a "pollution sponge" that concentrates those chemicals and poses a different, more insidious threat to marine and other life.
Evidence of the problem can be found as close to home as Tokyo Bay. That's where Hideshige Takada, a professor of organic geochemistry at Tokyo University of Agriculture and Technology — and one of the world's leading researchers on the interaction between plastic garbage and chemicals in the ocean — headed one windy morning this February to collect samples for his studies.
Looking like a grown-up version of the children collecting seashells nearby, Takada, 49, knelt with his nose centimeters from the sand, a pair of tweezers in one hand and a foil bag in the other. The object of his search was not shells, however, but plastic resin pellets — a form of marine plastic pollution he's been studying since 1998.
It's easy to overlook plastic resin pellets. Ranging in diameter from 1 mm to 5 mm, and in color from clear to dingy brown, they look a lot like overgrown sand. And, like sand, they're now found on beaches all around the world.
According to Charles Moore — a U.S. sea captain-turned-researcher who discovered the Eastern Garbage Patch in 1997 while crossing the Doldrums, a windless part of the ocean that mariners usually avoid — resin pellets account for around 8 percent of annual oil production and are the raw material for the 260 million tons of plastic the world uses each year (they're also used in smaller quantities for purposes such as cleaning pachinko balls and stuffing teddy bears). Lightweight, small, and seemingly harmless, they escape in untold volumes during transport and manufacture and eventually wash into the ocean. Once there, as a 2001 paper by Takada, colleague Yukie Mato and four other Japanese researchers first showed, they suck up a range of persistent organic pollutants (POPs).
Specifically, the 2001 paper focused on polychlorinated biphenyls (PCBs), a highly toxic group of industrial chemicals, and DDE, a degraded form of the pesticide DDT. Though PCBs are now banned, and in most countries DDT use is restricted, neither breaks down readily and both are still present in seawater. Additionally, these toxins have been found to accumulate on the seabed, where storms frequently stir them back into the water, rendering them again liable to be gobbled up by floating plastic debris.
Both PCBs and DDE have been proven to disrupt the endocrine system, the extremely sensitive set of glands and hormones that regulate functions such as insulin production, metabolism and sexual development. And now, they're showing up in plastic garbage that acts as a magnet to leach them out of the marine soup.
"Chemicals like PCBs and DDE are very hydrophobic," explains Takada. "That means they have a very high affinity for oily materials. Basically, plastics are solid oil. Therefore, plastic pellets accumulate hydrophobic pollutants with a concentration factor that's almost 1 million times (compared to the overall concentration of the chemicals in seawater)."
Takada uses pellets in his research because they are a uniform size and shape and therefore easy to study and compare. But he says that other types of plastic debris — which comprise a greater proportion of the plastic in the ocean and include everything from discarded fishing gear to stray shopping bags and fast-food cartons — display the same tendency as the pellets to absorb toxins....
What happens next to this poison-laden debris is less certain. Some pieces certainly sink to the deep ocean floor or are washed up on beaches. Others, however, have been found in the stomachs of sea creatures, including fish, birds, marine mammals and reptiles. Scientists believe some animals may actively select the pellets because they resemble fish eggs.
Whether the chemicals contained in them are then desorbed to digestive fluids and transferred to tissues in quantities significant enough to harm the animals that have eaten them is the subject of intense, but as yet incomplete, research.
That, though, doesn't stop some scientists from worrying.
"We should be very concerned," says Theo Colborn, founder of The Endocrine Disruption Exchange (TEDX), a U.S.- based organization that focuses on the health effects of endocrine-disrupting chemicals. Though these health effects are still the topic of much debate, she says a host of scientific studies have shown that even low-level exposure to endocrine disrupters may be linked to attention- deficit disorder, diabetes, falling fertility rates and more.
Hence Colborn is concerned that if fish eat toxic plastic, those same toxins may be absorbed into the bodies of people who eat the fish. "Endocrine-disrupting chemicals could also interfere with the ability of fish to reproduce," she adds.
Meanwhile, at the same time as plastic garbage is acting like a sponge for environmental pollution, research also shows it is releasing another set of chemicals into seawater — and possibly into the bodies of the creatures that eat it.
Chemicals like bisphenol A (BPA), nonylphenol and octylphenol are added to plastic for purposes such as fireproofing and stabilizing. But many of these additives are proven endocrine disrupters or carcinogens, and studies have shown beyond doubt that over time they can leach into seawater (just as they leach into drinking water kept in plastic containers).
It may be tempting to think of all these pollutants as literally drops in the ocean. Not so says sea captain Charles Moore, who has been studying the Eastern Garbage Patch since 1997 through the California-based Algalita Marine Research Foundation, a nonprofit organization he founded.
"Subtropical gyres (areas of circular motion) make up 40 percent of the ocean. That's 25 percent of the globe. All of them are accumulators of debris," he says.
In other words, although the Eastern Garbage Patch has been studied the most so far, it isn't the only oceanic rubbish dump out there. A Western Garbage Patch also exists several hundred kilometers off the coast of Japan, connected to the Eastern Garbage Patch by a "superhighway" of garbage, says Moore. In addition, he points to four more vortex-like gyres scattered around the globe.