'Nanoplastics' Could Be Worse Than Microplastics and We Know Almost Nothing About Them

Microplastics have recently entered the public consciousness for finding their way into our bodies and to some of the most remote places on Earth. But now, a much smaller, potentially much more nefarious, and less understood threat is drawing scientist’s attention—nanoplastics.

They’re not just tinier versions of the same scourge. Early research conducted over the past five years shows that they interact with the environment and living organisms in a totally different way than microplastics. Plus, we know very little about them. What researchers do know has some experts concerned. 

Microplastics are on the scale of micrometers, while nanoplastics are mere nanometers. To get a sense of just how small that is, imagine the difference between the size of a WNBA basketball (which is slightly smaller than the NBA equivalent) and a grain of rice. Whereas you can see microplastics on the tip of your finger, or under a regular microscope for the smaller bits, nanoplastics are nearly invisible.

Nanoplastics form when bigger pieces of plastic break down because of UV light, waves, natural enzymes, or other environmental factors. Researchers recently discovered that plankton and Antarctic krill in the oceans break down microplastics and turn them into nanoplastics. But plastic can also break down and get released into the air, for example when people repair sewer pipes. Once airborne, they can float for thousands of kilometers, as far as the Earth’s poles.

The infinitesimal size of nanoplastics is partly why scientists know little about them. “There’s been quite a lot of research on microplastics because they’re easier to detect, you just need a microscope. Nanoplastics are much smaller so you need special techniques to detect them,” environmental chemist Eric Lichtfouse told Motherboard in an interview. 

Professor of nanotoxicology Stacey Harper from Oregon State University, explained that the best methods so far rely on taking a lot of seawater and either running it through filters or chemically breaking down all its components and looking for chemical signatures of plastic. Filters become easily clogged by algae or other debris, and a chemical breakdown doesn’t give you a sense of the number of pieces of nanoplastic. 

That means, right now, we have no idea how many specks of nanoplastic there are floating or sloshing around the world. It’s likely they’ve been around more than 100 years, since the invention of plastic, even if scientists only started researching them in earnest in the past five years.

And without proper research on nanoplastics, it’s difficult to get a sense of how risky they are, said Harper. Risk takes into account exposure and toxicity, as well as some unknown factors. “Right now, for nanoplastics, we have no idea what the exposure looks like. On the toxicity side, we’re limited by the fact that most of the studies are done on polystyrene spheres. This is not what we’re exposed to,” she said. “We’re lacking information on everyday consumer products that break down.”

But what little we do currently know about them is worrisome both environmentally and in terms of health, said Lichtfouse, who penned an editorial titled "Nanoplastics are potentially more dangerous than microplastics." 

“If you go down to the nanoscale the properties of these materials are very different. They’re much more reactive,” he said. Smaller pieces means more surface area, which means more space for chemical components of plastic to leak out or react with other compounds in the environment. 

Plastics are essentially long chains of molecules, called monomers. When these monomers are linked together, like in PVC, they’re harmless. But on their own, like vinyl chloride for example, they can be toxic. Plus, the additives used to bind plastic together are usually also toxic and are released when the plastic is broken down. “Compared to a classical pollutant like a single molecule of pesticide, nanoplastics have many more different ways of being toxic,” said Lichtfouse.

And whereas bacteria, dirt, or pollutants might sit on top of a piece of microplastic, nanoplastics can act like sticky little buoys, grabbing onto all that nastiness. Harper says research is now starting to focus on where and how far nanoplastics can carry chemicals within the environment. “Those chemicals that are very concerning to us are very hydrophobic [meaning they don’t like water] so they like to associate with nanoparticles. What we’re starting to get into is how that changes the fate of the chemicals in the environment.”

When it comes to how nanoplastics might affect our health, most of what researchers know comes from studies done in petri dishes or other animals. Even then, most of those animals are small aquatic ones or ones that filter water to feed. We know very little about what nanoplastics do inside animals higher up the food chain, let alone in humans.

But since they’re so much smaller, nanoplastics can get into places that microplastics can’t. Where microplastics might get inside an animal’s organs, nanoplastics can get inside their cells. For comparison, proteins, which regularly zip in and out of cells, can range from three to 10 nanometers in size (although they’re not usually measured that way).

A 2023 study showed that nanoplastics attracted clumps of a particular protein, called alpha-synuclein, that has been linked to Parkinson’s disease and dementia. This happens in cells in a dish and lab mice. Earlier research in zebrafish found that nanoplastics can be passed from Mom to baby via the placenta and can cross the barrier to get into the brains of mice where they damage brain cells and alter the brain’s activity. 

Harper said that, based on her research on zebrafish, nanoplastics aren’t hugely toxic short-term. “Fish aren’t going belly up, even at really high concentrations,” she said. But there are no long term studies to tell us what constant contact with these foreign bodies might do. “This is what we’re all experiencing. Lifelong exposure to these particles. Ultimately that will lead to complications.”

Lichtfouse goes as far as to question how much certain diseases like cancer may be the result, at least in part, of nanoplastics. “If they’re more dangerous they might have led to more deaths because, for a lot of death and disease, we don’t know the real source. Epidemiologists just have probabilities,” he said.

“From the public point of view, this could be the next asbestos,” said Lichtfouse.

Harper is more cautious however. “I don’t know if I’d make a direct link to disease outcome but I will say that pathogenic bacteria really like plastics and so it kind of concentrates those bacteria that can lead to pathologies,” she said.

To start to get at those answers, Harper and other scientists are calling for more research, particularly around better methods for identifying nanoplastics. “It really needs full-throated effort to get some tools and techniques that will legitimately give us some answers to the number of particles that we’re continually exposed to.” That’s on top of realistic studies using milled-down plastics instead of polystyrene spheres, and long-term research.

She’s optimistic though that we’ll start to get some more clarity in the next few years. The research group she leads, Pacific Northwest Consortium on Plastics, has more than 300 members and the National Institute of Environmental Health Sciences has issued a plea for better understanding of nanoplastics’ effect on health. That, combined with legislative and international awareness, means “the momentum is shifting.”