The first comprehensive effort to estimate how much plastic pollution is going into the world’s oceans has come up with a staggering figure: As much as 13 million tons flow into the sea every year, and the annual pile could get 10 times bigger over the next decade.

Based on tonnage, China was judged the biggest plastic polluter among 192 coastal countries surveyed. Many of the others in the top 20 — such as No. 2 Indonesia and No. 3 Philippines — have fast-growing populations and economies. The United States ranked No. 20. But every nation could do more to stem the plastic tide, researchers said.

“It’s not about finger-pointing, but examining things that strongly influence a country’s rank on this list,” University of Georgia environmental engineer Jenna Jambeck told reporters here Thursday at the annual meeting of the American Association for the Advancement of Science. She’s the lead author for the survey, which is being published this week in the journal Science.

The survey combined country-by-country estimates for plastic production and disposal, as well as levels of waste mismanagement and litter, to come up with an estimate for the amount of plastic debris finding its way from land to sea. The range was 4.8 million to 12.7 metric tons for 2010, depending on assumptions about how much plastic waste makes its way from land to sea. The middle of the range is 8 million tons.

“Eight million metric tons of plastic — what does that look like?” Jambeck asked as she held up a plastic bag. “That’s the same as five bags filled with plastic for every foot of coastline in the world.”

Another author of the study, Kara Lavender Law of the Massachusetts-based Sea Education Association, noted that the annual global tuna catch amounted to roughly 5 million metric tons. “We are taking out tuna, and putting in plastic,” she said.