Researchers found between 12 million and 21 million metric tons of microplastic in just the top 200 meters of the Atlantic Ocean, according to a new study from the UK’s National Oceanography Centre. 

This means that the amount of plastic pollution in the Atlantic Ocean overall could be 10 times greater than previous estimates — up to 200 million metric tons.

“This finding itself is already very alarming because it tells us that there’s a lot more plastic in the ocean than we thought was there,” Katsia Pabortsava, co-author of the study, told Global Citizen. “It’s even more alarming from the perspective that this study only addresses three types of polymers at a very limited size, and also in a limited part of the ocean.”

The researchers decided to study microplastics in the Atlantic Ocean to make sense of the gap between the estimated amount of plastics released into the ocean and the amount actually reported to be in the waters.

In 2016 they embarked on an expedition from the UK to the Falkland Islands with a giant sieve that allowed them to search the ocean surface for tiny plastic fragments, some with diameters as small as half the diameter of a human hair. 

After taking samples from a dozen sites in the middle of the ocean, they extrapolated their findings to cover the area of the ocean they had studied. The researchers then realized that the scientific community had significantly underestimated the amount of plastic that was already in the ocean.

“People have said that over the last 65 years we’ve put about 17 million [metric tons] into the Atlantic,” co-author Richard Lampitt told Global Citizen. “But what we found was that just in the top 200 meters, and in a very specific size class, there was as much there as had ever been put in."

Since the researchers searched only the top 5% of the ocean and looked only at the three most common types of plastic, the total amount of plastic in the Atlantic Ocean is likely to be much greater than the already shocking 21 million metric tons. 

Taking into consideration all of the study’s limitations, the entire Atlantic Ocean could actually be carrying 200 million metric tons of plastic litter, according to the researchers.

“The previous estimates were wrong because, first, they only looked at the surface based on the assumption that plastics float; and second, they assumed that most of the plastic is in big particles because plastics don’t break down,” Lampitt said.

This new study is the first to measure these “invisible” microplastic particles beneath the ocean surface across the entire Atlantic, Pabortsava said. Microplastics form when larger pieces of plastic break down and erode into tiny particles, or when plastic fibers, such as those found in clothing, shred and disperse under pressure.

Since the study of microplastics is a relatively new field, there is still a lot that isn’t known about their potential harms. Recent studies, however, have shown the damage they can have on aquatic creatures when ingested. The tiny particles have now also been found in human organs.

Microplastics have contaminated practically every inch of the planet, said Peter Ross, vice president of research at Ocean Wise. They’re found in the earth’s air, water, soil, snowcaps, glaciers, wetlands, and even the most remote ocean trenches, Ross said. Given the widespread presence of microplastics in the environment, he’s not surprised by the study’s new numbers. 

“Plastic production has exploded — it’s up 20-fold over the last 40 years,” he told Global Citizen. “So even if recycling has improved, it’s been unable to keep up with the production and loss of plastic into the environment. With more and more plastic being produced, even with shoreline cleanups and recycling, we’re simply going to be fighting a losing battle.”

While ocean cleanup projects can help reduce the amount of larger pieces of plastic near the surface of the water, they cannot solve the problem of microplastic contamination in the deep sea. As this new study reveals the abundance of microplastics in the ocean already, the researchers urge countries to be smarter and more conscious about the use and disposal of plastic.

Public concern about plastic pollution has been growing for years now, and many countries and industries have made commitments to reduce single-use plastic. One of the UK’s largest supermarket chains is starting to switch out its plastic bags for paper versions. And Starbucks made headlines two years ago when it announced that it would phase out plastic straws by 2020.

Despite all of the progress, Lampitt notes that it is key to keep putting pressure on industries and businesses, and also to continue changing public attitudes toward plastic use.

“Plastic is an amazing, wonderful material,” he said. “But what we need to do is use less, reuse, recycle, and as a last resort, dispose of it in a safe way.”