The research claimed that many biodegradable products are unlikely to ever fully break down in the ocean, while labelling products as biodegradable could also make people more likely to dispose of them carelessly in the first place.

The executive director of the UN Environment Programme (UNEP) Achim Steiner said: “Recent estimates from UNEP have shown as much as 20 million tonnes of plastic end up in the world’s oceans each year.

“Once in the ocean, plastic does not go away, but breaks down into microplastic particles. This report shows there are no quick fixes, and a more responsible approach to managing the lifecycle of plastics will be needed to reduce their impacts on our oceans and ecosystems.”

The issue of microplastics being ingested by marine life has attracted publicity in recent years, with major UK retailers pledging to phase out harmful microbeads by 2017.

Industry reaction

However, the UN report has attracted criticism from the plastics industry, with the Oxo-biodegradable Plastics Association (OPA) saying: “The author is a geologist with no expertise in oxo-biodegradable plastics and we are disappointed that he did not ask the industry for information before publishing”.

The OPA added that conventional plastic will float around intact in the ocean for 50 years or more and then fragment, but the oxo-biodegradable versions will last for five years or less.

A recent report from the Plastic Disclosure Project, the UK Environment Assembly and natural capital analysts Truscot seemed to agree with the UN, in that a more holistic approach to the plastic lifecycle was needed, rather than a simple switch to biodegradable products.

The report argued that firms should be forced to pay the natural capital costs of plastics – up to $75bn a year in the consumer goods industry alone – as well as reporting on plastic use and disposal.

Brad Allen

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