27 million tons of nanoplastics, the most dangerous, are floating in the North Atlantic.

Nanoplastics are extraordinarily small particles (1 to 100 nanometers, smaller than the size of dust mites) that, precisely because of their size, can easily "sneak" into many places, from remaining suspended in the air we breathe to passing through our cellular barrier, settling in our organs . They can also reach us indirectly, through the meat or vegetables we eat. The problem: they are so small that scientists have trouble even making estimates; and the problem only grows, as the plastic waste generated every day is compounded by the disintegration of larger pieces into smaller parts.

Now, for the first time, a team of scientists has estimated how many nanoplastic particles there are in the North Atlantic Ocean alone. The data is not encouraging: a total of 27 million tons of these particles float in the strip that runs from the end of the Arctic Ocean to the equator and includes several Spanish coasts. This means that there are more of these tiny plastic "specks" than macroplastics and microplastics in the same area. The results have just been published in the journal Nature .

Plastics reach the ocean from rivers. But this isn't the only route: nanoplastics are also deposited in the oceans through the air, as suspended particles fall with rainwater or on their own, as "dry droppings." There, the larger plastics disintegrate under the influence of the sea, turning into these nanoparticles, which are known to directly harm marine plants and animals. They also settle on the seabed, where they can remain for tens, hundreds, and even thousands of years in some cases.

However, measuring nanoplastics has been a nearly impossible task until now: only a handful of studies have detected them in marine environments, focusing on coastal waters and the sea surface. The difficulties arise because nanoplastics are tiny, have very low masses, diverse chemical compositions, and behave differently than larger particles. To distinguish nanoplastics from the vast number of naturally occurring particles in the ocean, scientists need to develop methods to extract them from this marine "mixture" and then use advanced analytical techniques to detect and quantify them.

To make an estimate, the group led by Dušan Materić of the Helmholtz Centre for Environmental Research (Germany), in collaboration with scientists from the National Oceanography Centre in the United Kingdom, took samples of different waters at different depths during twelve stops across the ocean in 2020. The sample was taken by Sophie ten Hietbrink, a master's student at Utrecht University, who spent a month aboard the research vessel RV Pelagia. The samples were then filtered to remove any material larger than one micrometer (1,000 nanometers), and the work continued in the laboratory. "By drying and heating the remaining material, we were able to measure the characteristic molecules of different types of plastics using mass spectrometry," says Ten Hietbrink.

They found that, on average, the concentration of nanoplastics in the ocean's surface, specifically at a depth of 10 meters, was approximately 18.1 milligrams per cubic meter of water. However, samples taken near the seafloor showed a lower concentration of nanoplastics, 5.5 milligrams per cubic meter. The worst concentration was found near the coasts, where the concentration rose to 25 milligrams per cubic meter of water. With these results, Materić and his colleagues estimated that the total amount of nanoplastic pollution in the upper 10 meters of water in the North Atlantic is 27 million tons, which is what previous estimates considered for the entire ocean, up to the Southern Ocean (12.0 million tons of PET, 6.5 million tons of PS, and 8.5 million tons of PVC).

"This estimate shows that there is more plastic in the form of nanoparticles floating in this part of the ocean than in larger microplastics or macroplastics floating in the Atlantic or even in all the world's oceans," says Helge Niemann, a researcher at the Royal Netherlands Institute for Sea Research (NIOZ) and professor of geochemistry at Utrecht University.

The consequences of all these particles being present in these quantities in the water could be fundamental, Niemann emphasizes. “We already know that nanoplastics can penetrate deep into our bodies. They are even found in brain tissue. Now that we know they are almost ubiquitous in the oceans, it is also obvious that they penetrate the entire ecosystem: from bacteria and other microorganisms to fish and large predators like humans. More research is needed on how this pollution affects the ecosystem.”

In the future, Niemann and his colleagues also want to further study the different types of plastics that have not yet been found in the 1 micrometer fraction or smaller. "For example, we didn't find polyethylene or polypropylene among the nanoplastics. It's quite possible that these were masked by other molecules in the study. We also want to know if nanoplastics are as abundant in other oceans. We fear that they might be, but that remains to be seen."

The researcher emphasizes that the amount of nanoplastics in ocean water was a key missing piece, but now there's nothing that can be done about it. "The nanoplastics that are there can never be cleaned up. Therefore, an important message from this research is that, at the very least, we should prevent further plastic pollution of our environment."