Study provides first evidence that plastic nanoparticles can accumulate in the edible parts of vegetables

Plastic pollution represents a global environmental challenge, and once in the environment plastic can fragment into smaller and smaller pieces.

A new study shows for the first time that some of the tiniest particles found in the environment can be absorbed into the edible sections of crops during the growing process.

The research used radishes to demonstrate, for the first time, that nanoplastics – some measuring as little as one millionth of a centimetre in diameter – can enter the roots, before spreading and accumulating into the edible parts of the plant.

The researchers say the findings reveal another potential pathway for humans and animals to unintentionally consume nanoplastics and other particles and fibres that are increasingly present in the environment.

It also underscores the need for further research to investigate what is an emerging food safety issue, and the precise impacts it could have on environmental and human health.

The study – published in the journal Environmental Research – involved experts in plant science, environmental chemistry and plastic pollution from the University of Plymouth.

It applied similar techniques to those previously used by the team to demonstrate the rapid uptake of plastic nanoparticles by commercially important species of molluscs and fish, adding evidence that these particles can move and build up throughout the food chain.

For the new research, scientists placed radishes in a hydroponic growing system, with the plant’s non-fleshy roots in contact with a solution of polystyrene nanoparticles that contained radiolabeled carbon.

After five days, they examined how far into the plant the particles had penetrated, finding that nearly 5% of those originally in the solution had been retained by the root system – amounting to millions of nanoplastics entering the crop.

Of those particles, around a quarter had made their way into the edible fleshy roots, while 10% had accumulated in the leaves.

Dr Nathaniel Clark, Lecturer in Physiology at the University and the study’s lead author, said: “Plants have a layer within their roots called the Casparian strip, which should act as a form of filter against particles, many of which can be harmful. This is the first time a study has demonstrated nanoplastic particles could get beyond that barrier, with the potential for them to accumulate within plants and be passed on to anything that consumes them. There is no reason to believe this is unique to this vegetable, with the clear possibility that nanoplastics are being absorbed into various types of produce being grown all over the world.”

The University of Plymouth has pioneered research on microplastics for over 20 years, showing the presence of plastic particles from the deepest parts of the global ocean to the slopes of Mount Everest.

It has also identified some of the main sources of microplastic pollution – from tyre wear to the laundry cycle and flaking paint, and the degradation of larger items in the environment - with this research having directly informed international legislation.

Professor Richard Thompson OBE FRS, Head of the University’s International Marine Litter Research Unit and a senior author on the current study, said: “To some extent, these findings shouldn’t be a surprise – after all, in all our previous work we have found microplastic pollution everywhere we have looked for it. However, this study provides clear evidence that particles in the environment can accumulate not only in seafood but also in vegetables. This work forms part of our growing understanding on accumulation, and the potentially harmful effects of micro- and nanoparticles on human health.”