Plastic pollution in the ocean has long been a visible crisis, with images of bags, bottles, and nets entangling marine life. But new research reveals that the most widespread form of plastic pollution may be the kind that cannot be seen.
A study published in Nature on Wednesday estimates that the North Atlantic Ocean alone contains 27 million metric tons of nanoplastic—plastic particles 100 times smaller than the width of a human hair. According to the study’s authors, that figure is 10 times higher than previous estimates of plastic pollution of all sizes across all the world’s oceans.
Researchers from the Helmholtz Center for Environmental Research (UFZ), Utrecht University, and the Royal Netherlands Institute for Sea Research conducted the study, marking one of the first attempts to quantify marine nanoplastic pollution. Nanoplastics, defined as plastic particles less than 1 micrometer in size, were found to be present at all depths sampled, from surface waters to near the ocean floor.
“Plastic pollution of the marine realm is widespread, with most scientific attention given to macroplastics and microplastics. By contrast, ocean nanoplastics (<1 μm) remain largely unquantified, leaving gaps in our understanding of the mass budget of this plastic size class,” the authors of the study wrote. “Our findings suggest that nanoplastics comprise the dominant fraction of marine plastic pollution.”
The team collected samples during a 2020 research cruise aboard the RV Pelagia, sampling 12 locations across the North Atlantic at three depths: 10 meters below the surface, 1,000 meters deep, and 30 meters above the seafloor. They analyzed samples using thermal desorption and a high-resolution proton transfer reaction mass spectrometer (PTR-MS), combusting the nanoplastics to identify the gases released.
Lead author Dr. Dušan Materić, who developed the method at Utrecht University, explained that “each polymer has a unique chemical fingerprint by which both its concentration and identity can be determined.”
The analysis identified three primary types of nanoplastics. Polyethylene terephthalate (PET), used in plastic bottles and textiles, was the most widespread at every depth. Polyvinyl chloride (PVC), common in pipes, upholstery, and children’s toys, was also found, as was polystyrene (PS), used in plastic foam products.
At almost all measuring points, these types of plastic were detected in the uppermost layer of the ocean. “This is because, on the one hand, the redistribution from the atmosphere occurs via the sea surface and, on the other hand, a lot of plastic is introduced via the estuaries of rivers,” Materić explained.
Concentrations were highest closer to the surface, at 18 milligrams per square meter, and lowest near the seafloor, at about 5.5 milligrams per square meter. The lowest nanoplastic concentrations were found near the sea floor, but PET nanoplastics were detected at all points measured there, even at depths below 4,500 meters.
“They are present everywhere in such large quantities that we can no longer neglect them ecologically,” Materić said.
Notably, the study did not detect polyethylene (PE) or polypropylene (PP), the world’s two most common plastic polymers, likely due to limitations of the detection method. As a result, the researchers believe their estimate is conservative.
“This is in the same order of magnitude as the estimated mass of macro- and microplastics for the entire Atlantic,” Materić said.
Until now, quantitative data on nanoplastics in the world’s ocean was scarce. “Only a couple of years ago, there was still debate over whether nanoplastic even exists. Many scholars continue to believe that nanoplastics are thermodynamically unlikely to persist in nature, as their formation requires high energy. Our findings show that, by mass, the amount of nanoplastic is comparable to what was previously found for macro- and microplastic—at least in this ocean system,” Materić said.
The potential ecological and human health impacts of nanoplastics are profound. Due to their tiny size, nanoplastics can cross biological membranes more easily than microplastics, potentially leading to greater health risks. Studies suggest that nanoplastics cause inflammation to living cells when ingested, though it is unclear whether this is due to the particles themselves, chemicals they release, or pathogens they carry.
Tracey Woodruff, a professor of reproductive health and the environment at the University of California, San Francisco, who was not involved in the research, said she expects nanoplastics will be linked to many of the same health risks as microplastics. In animals, these include reproductive issues, intestinal problems, and colon and lung cancer. She warned, “Our hypothesis is that … nanoplastics could travel more widely in the body even than microplastics, and therefore could have more adverse health consequences.”
Helge Niemann, a researcher at the Royal Netherlands Institute for Sea Research and co-author of the study, stated nanoplastics are “not conducive, generally, for life.”
Martin Wagner, a biology professor at the Norwegian University of Science and Technology who was not involved in the study, said: “I would argue as a toxicologist that if you see something in micrograms per liter in the open ocean, that’s quite a high concentration.”
He cautioned, however, that the estimate relies on “very few samples,” but added, “It does make sense that you would find more nanoplastics than macro and microplastics.”
According to the United Nations, roughly 20 million tons of plastic enter aquatic ecosystems each year, much of which ends up in oceans.
“We’ve basically been dumping plastic in the ocean for decades,” Woodruff said. “It doesn’t go away, it just breaks down into smaller plastics, so it does make sense that you would find more nanoplastics than macro and microplastics.”
The findings have implications for upcoming UN plastics treaty negotiations, where world leaders will debate measures to address plastic pollution. Woodruff emphasized, “This reinforces how important it is to cap [plastic production], leave fossil fuels in the ground, and look to alternatives.”
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