Last year, according to National Geographic, the amount of garbage in the global oceans was estimated to be 245,000 tons. However, a study released in the journal “Science” earlier this month places the number between 20 and 2,000 times greater than the previous estimate. According to the study, 8 million tons of plastic entered the world’s oceans in 2010: the equivalent of five grocery bags for each foot of coastline.

Previous estimates of ocean trash were based on sample measurements from floating garbage patches in the ocean’s gyres (large regions of circular ocean currents where trash is prone to collecting). But not all plastic remains on the surface. The new study takes a different approach.

“What we have done,” said oceanographer Kara Lavender Law, a co-author of the study, “is look at the other side of the equation—what’s coming out of the faucet, rather than what’s already in the bathtub.”

The numbers on the faucet side are sizeable and still climbing. The 8-million-ton total is projected to increase to 155 million tons by the year 2025, if no changes are made to trash management—or plastic production.

Plastic production for use in consumer products began 50 years ago and has climbed progressively since then. According to National Geographic’s Laura Parker, the year 2012 saw 288 million tons of plastic materials produced around the world. The new study found that 4.8 to 12.7 million tons of that plastic enters the ocean as waste from 192 coastal countries annually.

As large as these numbers are, the amount of plastic reaching the ocean annually is only about 2 to 5 percent of coastal countries’ annual waste. The vast majority of garbage produced on land remains there. But 8 million tons, small fraction of the total though it is, remains a significant number in the context of global pollution.

The study in “Science” also identified the top culprit countries, in terms of how many tons of plastic entered the global oceans from each in a given year. China ranked first; the United States took the 20th spot. The remainder of the top 20 list includes 11 countries in Asia and five in Africa, Brazil and Turkey.

Despite highly developed waste management practices employed in the United States, the study cites a “high per capita waste generation” and a “large coastal population” as reasons for the country’s high ranking.

Large coastal populations are identified by the study as the root causes of the ocean’s plastic problem, as many of the nations contributing have less-developed means of managing garbage handling. But even in the developed world, plastics are still on the rise in consumer products and the packaging for those projects. The study calls for a revolution in waste management practices the world over.

Plastic is ubiquitous in consumer products and is on its way to becoming so in the global oceans as well.

“Ocean plastic has turned up literally everywhere,” Parker reported. “It has been found in the deep sea and buried in Arctic ice. It has been ingested with dire consequences by some 700 species of marine wildlife.”