27 Million Tons of Invisible Plastic Float in the North Atlantic

A sweeping study led by the Royal Netherlands Institute for Sea Research and Utrecht University puts the mass of nanoplastics drifting in the North Atlantic Ocean at roughly 27 million tons — more plastic than is estimated to exist as larger micro- and macroplastics anywhere in the ocean.

For years, the ocean's plastic budget has been dominated by visible debris: the great patches of surface litter, the microplastics that turn up in fish, in salt and in drinking water. Nanoplastics — particles smaller than one micrometer, roughly a thousand times thinner than a human hair — have been almost invisible to scientists. They pass through standard filtration nets and resist the counting methods used for larger plastic fragments, so no reliable mass estimate had ever been made.

Key finding: By measuring nanoplastic concentrations at 12 locations from the Azores to the European continental shelf, researchers estimate the well-mixed surface layer of the North Atlantic alone contains about 27 million tons of nanoplastics — exceeding the mass of all larger floating plastic in the Atlantic, and likely all oceans combined.

How they measured the invisible

The study began with a four-week expedition aboard the research vessel Pelagia. At each sampling site, water was filtered to remove everything larger than one micrometer, leaving behind only the nano-sized fraction. The residue was then dried and heated, releasing the characteristic molecular signatures of specific plastics — polystyrene (PS), polyvinyl chloride (PVC) and polyethylene terephthalate (PET). By reading which molecules appeared, the team could quantify exactly how much of each polymer was present in each sample.

Those measurements, collected along a transect spanning open-ocean gyre waters to the shelf near Europe, were then extrapolated across the entire North Atlantic's mixed surface layer. The result was a conservative estimate of 27 million tons — and the team stresses the number likely understates the true total, since the methods only captured a subset of plastic types.

Why it matters

Nanoplastics cross biological barriers that larger particles cannot. At less than a micrometer, they can penetrate cell membranes and enter organisms from plankton upward through the food chain. Because they are pervasive and persistent, they raise concerns for marine ecosystems and, by extension, for human exposure through seafood and drinking water.

The discovery reframes ocean pollution: the dominant plastic fraction is no longer the visible one, but the invisible nano fraction — and quantifying it is the essential first step toward managing it. Following the publication, a major grant was awarded to extend the work and track how nanoplastics move, settle and break down in the sea.

The results were published in Nature by a team led by researcher Helge Niemann of NIOZ and Utrecht University.

Knowledge takeaway: An estimated 27 million tons of nanoplastics (under 1 micrometer) float in the North Atlantic's surface layer, more than the mass of larger micro- and macroplastics; nanoplastics were detected by filtering sub-micron residue and reading polymer molecular signatures with heat; their tiny size lets them cross cell barriers, making them the dominant and most ecologically consequential ocean-plastic fraction.