The Hidden Burden: Nanoplastics Across the North Atlantic

Marine plastic pollution is no longer a distant threat—it's here, pervasive, and far smaller than we once imagined. While public debate and scientific research have focused on macroplastics and microplastics (particles larger than 1 μm), a new study in Nature reveals that nanoplastics—particles smaller than a micrometer—are widespread across the North Atlantic Ocean. These particles are not just microscopic debris; they are so tiny that they can cross biological membranes, interact rapidly with other chemicals, and potentially accumulate in marine organisms and, ultimately, in our food chain.

In a groundbreaking effort, scientists quantified the concentrations, distribution, and potential mass of nanoplastics in one of the planet's most studied yet least understood marine regions. The results demand a rethink of global plastic budgets and pollution mitigation strategies.

A Missing Piece in the Plastic Puzzle

For decades, scientists have tried to reconcile the amount of plastic entering the ocean with the amount actually detected. The numbers never matched—vast quantities seemed to be missing. Nanoplastics, due to their size, have been largely absent from these mass balances. Their invisibility to traditional sampling methods meant that even “clean” waters might contain significant loads.

The Nature study, led by Sophie ten Hietbrink (Stockholm University) and colleagues from Utrecht University, NIOZ, and other institutions, asked a simple but crucial question: How much nanoplastic is in the North Atlantic, and where is it concentrated?

Mapping Nanoplastic Concentrations

The research team sampled 12 hydrographic stations along a transect spanning from the subtropical gyre to the European continental shelf. They collected water at three depths: the surface mixed layer (~10 m), intermediate waters (~1,000 m), and near-bottom waters (30 m above the seabed).

Using advanced filtration and chemical fingerprinting techniques, they targeted three common polymers: polyethylene terephthalate (PET), polystyrene (PS), and polyvinyl chloride (PVC). Concentrations were reported in milligrams per cubic meter (mg·m⁻³), with rigorous quality control and Monte Carlo simulations to account for potential overestimations from organic background material.

Key findings:

• Ubiquity: Nanoplastics were present at all stations and depths.
• Surface dominance: Mixed layer concentrations averaged 18.1 ± 2.1 mg·m⁻³, about 1.4 times higher than in intermediate waters.
• Coastal peaks: Coastal waters showed ≳1.5 times higher concentrations than open ocean sites, with maxima near the European coast.
• Deep presence: PET dominated in deep waters (~5.5 ± 0.6 mg·m⁻³), showing that these particles can sink and persist far below the surface.

A Mass Beyond Expectations

By extrapolating their measurements to the entire mixed layer of the temperate–subtropical North Atlantic, the researchers estimate a staggering 27 million tonnes of nanoplastics in just that portion of the ocean. This mass alone exceeds previous estimates for the total macro- and microplastic load in the same region.

This finding challenges long-standing assumptions in marine pollution research. If nanoplastics make up the largest share of the plastic mass in the ocean, then past assessments have significantly underestimated total plastic pollution.

Why This Matters for Policy and Public Health

Nanoplastics’ small size gives them unique environmental and biological properties:

• Ecosystem penetration: They can interact with plankton, fish larvae, and other small organisms, potentially altering food web dynamics.
• Chemical interactions: Their large surface area relative to volume allows them to adsorb pollutants or leach additives more efficiently than larger particles.
• Human exposure: They may reach humans through seafood consumption, inhalation of sea spray, or other pathways.

For policymakers, this study underscores the need to:

1. Expand monitoring to include nanoplastic fractions in marine surveys.
2. Regulate upstream sources, including industrial emissions and plastic fragmentation processes.
3. Integrate nanoplastics into risk assessments for marine and human health.

As the authors stress, focusing solely on visible debris and larger microplastics is no longer enough. Tackling the invisible fraction is essential for meaningful progress.

Next Steps for Research

• Standardized sampling methods for nanoplastics.
• Improved analytical tools to detect particles reliably at submicron scales.
• Studies of real-world ecological and toxicological impacts at environmentally relevant concentrations.
• Source identification, including rivers, atmospheric deposition, and in-ocean fragmentation.

These steps could help clarify how nanoplastics move through marine systems, how long they persist, and which sources are most significant—critical knowledge for developing targeted mitigation strategies.

Conclusion

This Nature study delivers a clear message: the plastic problem is not just on the surface—it is embedded in every layer of our oceans, down to the smallest measurable particles. With nanoplastics potentially representing the largest fraction of plastic mass in the sea, the urgency for comprehensive monitoring and action has never been greater.

It is no longer enough to clean up what we can see. We must also confront the pollution we cannot.

Topics of interest

Pollution