Tiny plastic particles in the environment: Nanoplastics - an underestimated problem?
These images speak to each of us: huge whirlpools of plastic waste in the world's oceans with sometimes devastating consequences for their inhabitants - the legacy of our modern lifestyle. Weathering and degradation processes produce countless tiny particles that can now be detected in virtually all ecosystems. But how dangerous are the smallest of them, so-called nanoplastics, really? In the latest issue of the journal Nature Nanotechnology, a team from Empa and ETH Zurich looks at the state of current knowledge (or lack thereof) and shows how these thoroughly important questions should be addressed.
Wherever scientists look for them, they find them: Whether in remote mountain lakes, in Arctic sea ice, in deep-sea soils or in air samples, even in edible fish - thousands upon thousands of microscopic plastic particles in the micro to millimeter range. This microplastic is now even considered one of the defining characteristics of the Anthropocene, the age of the Earth shaped by modern humans.
Microplastics are formed by weathering and physicochemical or biological degradation processes from macroscopic plastic products, such as the tons of plastic waste in the oceans. It is unlikely that these comminution processes will stop at the micrometer scale. And so there is growing concern everywhere about the potential negative effects nanoplastics could have on various ecosystems. "Many media reports suggest, through their sometimes very emotional coverage, that we are facing a huge problem there," says Empa researcher Bernd Nowack, who has long studied the material flows of synthetic micro- and nanoparticles, for example from textiles or tire abrasion, into the environment. But Nowack says this statement can hardly be scientifically substantiated at present: "We don't even know how much nanoplastics are present in the first place."
Huge gaps in knowledge ...
This is primarily because it is enormously difficult in terms of measurement technology to identify artificial nanoparticles from plastic in environmental samples with thousands and thousands of (natural) particles of similar size without any doubt. Appropriate analytical methods would first have to be developed, says Denise Mitrano of ETH Zurich. And then it would be a matter of understanding exactly what risk the tiny plastic particles - some of which differ considerably in their chemical composition - pose to humans and the environment, in other words: how dangerous they ultimately are. Says Nowack, "So we can't justifiably say we have a problem here - but we also can't say it's not."
That's because the smaller particles become, the more likely they are to reach organs and tissues that are inaccessible to larger particles. The blood-brain barrier or placenta, for example, keeps particles and macromolecules out of the bloodstream until they reach a certain size - or rather, smallness - thereby protecting the tissues and organs "behind" them, i.e. the brain and fetus, respectively, from potentially dangerous substances such as viruses and bacteria. "Even if we ingest microplastics, for example through our food, they probably do not enter our bloodstream or our brain, but are simply excreted again," says Peter Wick, head of Empa's Particles-Biology Interactions laboratory, which studies the influence of nanoparticles on biological systems. "With nanoplastics, we can't be so sure."
... and a great need for research
Mitrano, Wick and Nowack conclude that because of the enormous gaps in knowledge, further research into nanoplastics is absolutely essential. However, this should be done as systematically and broadly as possible - and with a cool head. After all, emerging pollutants do not always turn out to be as dangerous as originally assumed. "When it comes to many things that are new and unknown, our society initially adopts a zero-risk attitude," Wick says. And that's understandable, he said, especially in the case of nanoplastics, because "who wants plastic in their food?"
The solution to the problem, however, is as simple (at least in theory) as it is complex. For one thing, a large proportion of nanoplastic particles are created from the degradation of macro- and microplastics. Less plastic in the environment therefore reduces the amount of nanoplastics, and here every individual can contribute to not further polluting the environment with plastic waste. On the other hand, nanoplastics can also be created directly during the use of plastic products - for example through abrasion - without the user being able to do anything about it. Indeed, it is not possible to do completely without plastic. "The various polymers simply have too many positive properties for that," says Bernd Nowack.
Original publication: Nature Nanotechnology: Mitrano et al. (2021) – Placing nanoplastics in the context of global plastic pollution
Image source: Flickr.com: Kevin Krejci – Plastic Ocean