We knew that microplastics—the tiny pieces of broken-down plastic bottles and other garbage—can now be found everywhere from Arctic ice to bottled water to seafood. But it turns out that it’s even more common in the ocean than scientists previously feared. In a recent study , researchers from Scripps Institution of Oceanography analyzed samples of ocean water and estimated that each cubic meter of water may be contaminated by a million times more pieces of microplastic than previous studies suggested.

Researchers usually count microplastic by running a net with a very fine mesh behind a boat; the mesh is small enough to catch plastic as small as a third of a millimeter in diameter. “That sounds super small, and it is small,” says Jennifer Brandon, the lead author of the study, who did the research as a graduate student at Scripps and now works as a senior scientist at Applied Ocean Sciences. “But . . . it is actually cutting off a vast size range of the plastic.”

As plastic breaks down into smaller and smaller pieces, it never fully disappears. “We realized that it was out there, but it’s just smaller than we were capturing,” she says. To collect pieces that would escape through a net, Brandon used a stainless steel bucket to take samples of water, and then used custom polycarbonate filters in the lab to capture the extra-small plastic. The pieces were so small that they couldn’t easily be identified, even with a microscope, so the researchers used technique that looks for the unique fluorescent properties of the material. Older studies had estimated that in a cubic meter of ocean water, there are 10 pieces of larger microplastic. The new study estimates that there are 8.3 million pieces of the smaller microplastic in the same amount of water.

The scientists also studied salps, a type of plankton that feeds on tiny particles of food in the same size range as microplastics. Every salp studied contained microplastics (those closest to shore were filled with more plastic than those in the Great Pacific Garbage Patch, surprisingly). It’s not clear yet what that means for their health, or for the fish or crabs that eat them, or the people that eat those animals. The average person now eats, by one estimate, at least 50,000 pieces of microplastic a year, and probably far more. Some studies have already shown that plastics can travel up the food chain and are linked to brain damage and liver tumors in fish. Other studies are underway.

Though projects like the Ocean Cleanup nonprofit attempts to collect larger pieces of plastic from the ocean—before those pieces of trash can break down—there isn’t yet a way to clean up the smallest particles. Until there is, the best answer is to prevent even more plastic garbage from entering the ocean in the first place. “I think investing at the prevention level right now is the best bang for your buck, and then figuring out the next wave of the technology we’re going to use to take these tiny things out of the ocean,” she says.