China ranked top polluter as figures suggest total plastic litter ending up in the seas could rise tenfold by 2025.
Coastal populations put about 8m tonnes of plastic rubbish into the oceans in 2010, an annual figure that could double over the next decade without major improvements in waste management efforts, scientists warn.
The mountain of plastic litter, including bags, food packaging and toys, was equivalent to five full shopping bags of debris for every foot of coastline bordering nearly 200 countries the team studied.
Though researchers have known about plastic waste in the oceans for 40 years, the latest report, published in the journal Science, is the first to attempt a detailed estimate of how much plastic made on the planet finds its way into the oceans.
The figures suggest that about 10 to 30 times more plastic debris ends up in the oceans than surveys have found floating about on the surface. In one recent survey, an international team reported more than 5 trillion pieces of plastic are floating in the world’s oceans, collectively weighing nearly 269,000 tonnes.
In the latest study, researchers at the University of Georgia and the Sea Education Association in Massachusetts calculated the amount of waste plastic generated in 192 countries with coastlines on the Atlantic, Pacific and Indian Oceans, and the Mediterranean and Black seas. From data on regional manufacturing and waste management practices, they worked out that 4.8m to 12.7m tonnes of plastic rubbish wound up as ocean debris in 2010.