A new report from the United Nations says plastics labelled biodegradable rarely disintegrate in the ocean because they require industrial composters and prolonged exposure to high temperatures to break down.

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

Biodegradable plastics were created to help reduce waste. However, the report released this week says some polymers need to be exposed to prolonged temperatures of above 50 C to disintegrate.

Peter Kershaw is one of the authors of the report. (Peter Kershaw)

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 take two or three years for some biodegradable plastics to disintegrate.

"Essentially the ocean is being used as a waste basket and the waste basket 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," Kershaw says. "Because if you mix biodegradable with standard plastics you can compromise the properties of the original plastic."

A lot of the plastic that WWF-Canada finds on the country's shorelines are from every day waste, such as grocery bags, food wrappers and water bottles. (WWF-Canada)

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 of World Wildlife Fund Canada.

"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," said Miller.

'In the Arctic, because the ice traps them, the abundance of microplastics are at least three times more than in other areas in oceans,” says David Miller the President and CEO of WWF-Canada. ( WWF-Canada)

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."

Miller says a lot of the plastic that WWF-Canada finds on shorelines is 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.