An estimated 414 million pieces of plastic -- including nearly one million shoes and 370,000 toothbrushes -- have been found washed ashore on the beaches of remote Cocos (Keeling) Islands in the Indian Ocean, according to a study.
The survey of plastic pollution, published in the journal Scientific Reports, estimated that the beaches on the islands are littered with 238 tonnes of plastic.
Remote islands which do not have large human populations depositing rubbish nearby are an indicator of the amount of plastic debris circulating in the world's oceans, said Jennifer Lavers from the Institute for Marine and Antarctic Studies (IMAS) at the University of Tasmania in Australia.
"Islands such as these are like canaries in a coal mine and it's increasingly urgent that we act on the warnings they are giving us," Lavers said.
Plastic pollution is now ubiquitous in our oceans, and remote islands are an ideal place to get an objective view of the volume of plastic debris now circling the globe, researchers said.
"Our estimate of 414 million pieces weighing 238 tonnes on Cocos (Keeling) is conservative, as we only sampled down to a depth of 10 centimetres and couldn't access some beaches that are known debris 'hotspots'," said Lavers.
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Her research in 2017 revealed that beaches on remote Henderson Island in the South Pacific had the highest density of plastic debris reported anywhere on Earth.
While the density of plastic debris on Cocos (Keeling) Islands beaches is lower than on Henderson Island, the total volume dwarfs the 38 million pieces weighing 17 tonnes found on the Pacific island.
"Unlike Henderson Island, where most identifiable debris was fishing-related, the plastic on Cocos (Keeling) was largely single-use consumer items such as bottle caps and straws, as well as a large number of shoes and thongs," Lavers said.
Study co-author Annett Finger from Victoria University said global production of plastic continues to increase, with almost half of the plastic produced over the past 60-years manufactured in the last 13 years.
"An estimated 12.7 million tonnes of plastic entered our oceans in 2010 alone, with around 40 per cent of plastics entering the waste stream in the same year they're produced," Finger said.
"As a result of the growth in single-use consumer plastics, it's estimated there are now 5.25 trillion pieces of ocean plastic debris," said Finger.
Plastic pollution is a well-documented threat to wildlife and its potential impact on humans is a growing area of medical research.
The scale of the problem means cleaning up our oceans is currently not possible, and cleaning beaches once they are polluted with plastic is time consuming, costly, and needs to be regularly repeated as thousands of new pieces of plastic wash up each day, researchers said.
"The only viable solution is to reduce plastic production and consumption while improving waste management to stop this material entering our oceans in the first place," Finger said.