Wednesday, July 09, 2025

Underestimated sources of marine pollution

A study published in Nature reveals for the first time the extent to which nanoplastic pollutes the North Atlantic.

Helmholtz Centre for Environmental Research - UFZ

Plastic waste pollutes oceans across all regions of the world. Marine animals may become entangled in larger plastic debris such as nets and bags or mistake smaller pieces for food. Ingested plastic can block or injure the gastrointestinal tract. The smallest plastic particles in the micro and nano range are mostly excreted, but a small proportion can pass through the intestinal wall and enter the bloodstream.

So how much nanoplastic is actually present in the oceans? Most scientific attention has so far been focussed on macro- and microplastic because their larger size makes them easier to study. Quantitative data on the pollution of the oceans by nanoplastic particles smaller than 1 µm have been scarce until now because the particles are very small, prone to change, and often difficult to distinguish from other environmental particles using standard methods.

During a 2020 expedition aboard the RV Pelagia, the largest Dutch research vessel and flagship of the NIOZ, researchers from the UFZ and Utrecht University recorded the occurrence of nanoplastic along a transect from the European continental shelf to the subtropical North Atlantic Gyre. Samples were taken at 12 measuring points: in the uppermost water layer at around 10 m, in the intermediate layer at around 1,000 m, and 30 m above the seabed. “With the data from these measuring points, we can make statements about the vertical and horizontal distribution of nanoplastic in the North Atlantic”, says Dr Dušan Materić, chemist at the UFZ and lead author of the study.

Led by Materić, the scientists used a high-resolution proton transfer reaction mass spectrometer (PTR-MS) coupled with thermal desorption (TD) to measure the concentrations of organic trace gases. With this TD-PTR-MS, the tiny plastic particles in the samples can be combusted. By heating them, gases are released; these can then be quantified in the mass spectrometer. According to Materić, who developed the method in 2020 while working at Utrecht University, because each polymer produces a distinct chemical fingerprint, its identity and concentration can be reliably determined.

The researchers detected nanoplastic at all depths analysed across the 12 measurement sites. “They are present everywhere in such large quantities that we can no longer neglect them ecologically”, says Materić. The research team most frequently found nanoparticles of polyethylene terephthalate (PET), polystyrene (PS), and polyvinyl chloride (PVC), which are commonly used in disposable and reusable plastic bottles, films, drinking cups, and cutlery. At nearly all measuring points, the researchers detected these types of plastic in the uppermost water layer. “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”, says Materić. The intermediate layer (i.e. the layer between the oxygen-rich surface water and the oxygen-depleted deep water) is dominated by PET nanoparticles. According to Materić, a higher concentration of nanoplastic was found in the North Atlantic subtropical gyre, an area where surface microplastics are known to accumulate because of ocean currents.

The researchers found the lowest concentrations of nanoplastic in the water layer near the sea floor. They detected PET nanoplastic at all measuring points there – even at depths of more than 4,500 m. This nanoplastic most likely originated from the fragmentation of synthetic clothing fibres but possibly also from previously unknown processes. “Nanoplastic and nanoparticles are so small that the physical laws governing larger particles often no longer apply”, says Materić.

The research team were surprised to find no polyethylene (PE) or polypropylene (PP) at any of the measuring points. Both PE and PP are commonly used in bags and packaging, which often end up as marine plastic waste. “There is a lot of PE/PP microplastic on the sea surface, but we did not find any PE/PP nanoparticles that could have been formed as a result of solar radiation or abrasion by the waves”, says Materić. The PE and PP nanoplastic may be mineralised or molecularly altered to such an extent that they are no longer detected as plastic by the PTR-MS, or there might be some other dynamic sedimentation and removal processes we are not yet aware of.

The scientists extrapolated the mass of nanoplastic in the North Atlantic from the concentration measurements. Based on these results, around 27 million tonnes of nanoplastic – 12.0 million tonnes of PET, 6.5 million tonnes of PS, and 8.5 million tonnes of PVC – are stored in the uppermost water layer of the North Atlantic, up to 200 m deep, from the temperate to the subtropical zone. “This is in the same order of magnitude as the estimated mass of macro- and microplastics for the entire Atlantic”, says Materić. This means that nanoplastic accounts for a large proportion of plastic pollution in the oceans and has not yet been factored into current assessments of the marine plastic balance. “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”, says Materić.

Journal

Nature

DOI

10.1038/s41586-025-09218-1

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Nanoplastic concentrations across the North Atlantic

Article Publication Date

9-Jul-2025

Tremendous amount of plastic floats as nanoparticles in the ocean

Answer to the paradox of the missing plastic

Royal Netherlands Institute for Sea Research

“This estimate shows that there is more plastic in the form of nanoparticles floating in the this part of the ocean, than there is in larger micro- or macroplastics floating in the Atlantic or even all the world's oceans!”, said Helge Niemann, researcher at NIOZ and professor of geochemistry at Utrecht University. Mid-June, he received a grant of 3.5 million euros to conduct more research into nanoplastics in the sea and their fate.

Ocean expedition
For this research, Utrecht master student Sophie ten Hietbrink worked for four weeks aboard the research vessel RV Pelagia. On a trip from the Azores to the continental shelf of Europe, she took water samples at 12 locations where she filtered out anything larger than one micrometer. “By drying and heating the remaining material, we were able to measure the characteristic molecules of different types of plastics in the Utrecht laboratory, using mass spectrometry,” Ten Hietbrink says.

First real estimate
The research by NIOZ and Utrecht University provides the first estimate of the amount of nanoplastics in the oceans. Niemann: “There were a few publications that showed that there were nanoplastics in the ocean water, but until now no estimate of the amount could ever be made.” This first estimate was made possible, according to Niemann, by the joining of forces of ocean scientists and the knowledge of atmospheric scientist Dusân Materic of Utrecht University.

Shocking amount
Extrapolating the results from different locations to the whole of the North Atlantic Ocean, the researchers arrived at the immense amount of 27 million tons of nanoplastics. “A shocking amount,” Ten Hietbrink believes. “But with this we do have an important answer to the paradox of the missing plastic.” Until now, not all the plastic that was ever produced in the world could be recovered. So, it turns out that a large portion is now floating in the water as tiny particles.

Sun, rivers and rain
The nanoplastics can reach water by various routes. In part, this happens because larger particles disintegrate under the influence of sunlight. Another part probably flows along with river water. It also appears that nanoplastics reach the oceans through the air, as suspended particles fall down with rainwater or fall from the air onto the water surface as ‘dry deposition’.

Consequences
The consequences of all those nanoplastics in the water could be fundamental, Niemann emphasizes. “It is already known that nanoplastics can penetrate deep into our bodies. They are even found in brain tissue. Now that we know they are so ubiquitous in the oceans, it's also obvious that they penetrate the entire ecosystem; from bacteria and other microorganisms to fish and top predators like humans. How that pollution affects the ecosystem needs further investigation.”

Other oceans
In the future, Niemann and colleagues also want to do further research on, for example, the different types of plastics that have not yet been found in the fraction of 1 micrometer or smaller. “For example, we have not found polyethylene or polypropylene among the nanoplastics. It may well be that those were masked by other molecules in the study. We also want to know if nanoplastics are as abundant in the other oceans. It is to be feared that they do, but that remains to be proven.

Not cleaning up but preventing
Niemann emphasizes that the amount of nanoplastics in ocean water was an important missing piece of the puzzle, but now there is nothing to do about it. “The nanoplastics that are there, can never be cleaned up. So an important message from this research is that we should at least prevent the further pollution of our environment with plastics.”

The research vessel Pelagia

Credit

NIOZ

Dried sample vials with salt residue.

Credit

Sophie ten Hietbrink