Biodegradable plastic items such as bags and water bottles break down extremely slowly in marine environments, a United Nations report found. Therefore, they are "false solutions" to the global plastic pollution.

The "greener" plastics have been positioned to replace their non-biodegradable counterparts that often end up in large plastic waste mountains in the oceans. However, what is thought to be a simple solution to a global crisis isn't that simple after all.

"A lot of plastics labelled biodegradable, like shopping bags, will only break down in temperatures of [50 degrees Celsius] and that is not the ocean," said U.N. Environment Program Chief Scientist Jacqueline McGlade.

The biodegradable plastics do not float so they end up sinking. Therefore, the lack of UV exposure will not break them down, McGlade added.

"Weathering and fragmentation is enhanced by exposure to UV irradiation. The process becomes extremely slow once this is removed, as in much of the ocean. Plastics marked as 'biodegradable' do not degrade rapidly in the ocean," said the U.N. report (PDF).

Because of its extremely durable nature, the majority of them end up in large mountains of plastic debris in the ocean. And it's not just the plastic bottles and shopping bags that are creating major concerns.

Several "microplastics," which are usually in the form of "microbeads" or "micro-exfoliates" also end up in the oceans, which could also endanger marine life. Moreover, the ocean currents spread them around the world.

Apart from the high possibility of getting caught in floating plastic wastes, marine animals can also ingest these microbeads and enter the human food chain.

These particles are often released into the wastewater systems after washing or directly into the marine environments through recreational bathing.

Microplastics can also disrupt the marine ecosystem. For instance, jellyfish use plastic waste to extend their range when they travel. Their expansion is not just bad for the swimmers near the coasts, but these marine invertebrates also consume the food meant for the marine life in the new areas they end up in.

In 2014 alone, more than 300 million tonnes of plastic products were produced, said the U.N. report. Given the current production and usage trends, this rate can surge to approximately 2,000 million tonnes by 2050.

The U.N.'s 179-page report titled "Marine Plastic Debris And Microplastics" was published in time for the agency's environment assembly. The event kicked off on May 23 and will conclude on May 27 in Nairobi, Kenya.

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