Up to 240,000 tonnes of plastic particles are polluting the world's oceans — at least three times more than previous estimates.

Credit: Richard Whitcombe/Alamy

Each year, 5 million to 13 million tonnes of plastic ends up in the sea, where it slowly degrades into microplastic particles that threaten marine ecosystems. Erik van Sebille at Imperial College London and his colleagues analysed 40 years of data on plastic collected from surface-trawling plankton nets — more information than in previous studies. By combining those data with sophisticated ocean-circulation models, they estimated that the oceans contain 93,000–236,000 tonnes of microplastic particles.

This represents just 1% of ocean plastic: the rest lies intact (pictured) on the sea floor or shore, or trapped in marine organisms, the authors suggest.

Environ. Res. Lett. 10, 124006 (2015)