Biodegradable plastics not breaking down in ocean, UN report says

A new report from theUnited Nationssays plastics labelled biodegradable rarely disintegrate in the ocean because they require industrialcompostersand prolonged exposure to high temperatures to break down.

Plastic waste is a serious concern in the world's oceans, where as much as 20 milliontonnesof plastic ends up each year, according to recent estimates from the United Nations Environment Programme.

• 'Great Pacific Garbage Patch' researchers devastated by sight
• Plastics dumped in world's oceans estimated at 8Mtonnesannually

Biodegradable plastics were created to help reduce waste.However,thereport released this weeksayssome polymers need to be exposed to prolonged temperatures of above 50C to disintegrate.

These conditions are hard to come by in nature, says Peter Kershaw, one of the authors of the study.

"When you get in the ocean, the rates of degradation are even lower because UV light penetration is very limited," said Kershaw.

"It's cold, there's less oxygen. So once it's in the sea it's just going to stay there for an extremely long period of time."

Kershaw says it could taketwo or three years for some biodegradable plastics to disintegrate.

"Essentially the ocean is being used as a waste basket and the wastebasket is getting fuller and fuller, and so the impacts of that plastic litter are just going to keep on increasing."

Forget recycling

The report says biodegradable plastic also poses a problem for recycling.

"If you're recycling plastic you don't want to have anything to do with biodegradable plastics," Kershawsays. "Because if you mix biodegradable with standard plastics you can compromise the properties of the original plastic."

He says even when biodegradable plastic does disintegrate, the fragments can pose a threat to ocean life.

"Each of those fragments then behaves exactly the same way as a standard piece of polyethylene," adds Kershaw.

"The objects may disintegrate, but you're still left with an awful lot of microplastics and those have their own problems in terms of impact on the environment."

Some evidence also suggests that labelling products as 'biodegradable' increases people's tendency to litter because they think they are not creating waste.

Arctic ice compounds the issue

Plastic distributes toxic chemicals throughout Canada's oceans, says David Miller,president and CEO ofWorld Wildlife FundCanada.

"It can have an impact on all sorts of marine life, from marine mammals to corals, and of course it can get ingested and become part of the food chain," saidMiller.

In the Arctic,ice compounds the issue.

"In the Arctic, because the ice traps them, the abundance of microplastics are at least three times more than in other areas in oceans, including the Great Pacific Garbage Patch, which is THE concentration of plastics."

• Arctic sea ice polluted with microplastics

Miller says a lot of the plastic that WWF-Canada finds on shorelinesis from everyday waste, such as grocery bags, food wrappers and water bottles.

"What we can do, each of us, is dramatically reduce the amount of plastic we use; the second thing is to dispose of it properly,"said Miller.

He adds that the good news is that more and more organizations are getting involved in clean up efforts to help restore our coastlines, such as the Great Canadian Shoreline Cleanup in Iqaluit this past June.