Researchers find the foodchain soiled by plastics

A study from the University of Eastern Finland shows that lettuce can take up nanoplastics from the soil and transfer them into the food chain.

The concern about plastic pollution has become widespread as mismanaged plastics in the environment break down into smaller pieces known as microplastics and nanoplastics. It is likely that nanoplastics can pass through physiological barriers and enter organisms.

“Our results show that lettuce can take up nanoplastics from the soil and transfer them into the food chain. This indicates that the presence of tiny plastic particles in soil could be associated with a potential health risk to herbivores and humans if these findings are found to be generalisable to other plants and crops and to field settings. However, further research into the topic is still urgently needed,” said lead author Dr Fazel Monikh of the University of Eastern Finland.

An Australian lab was opened in Queensland in March to measure micro and nanoplastics in humans. The University of Queensland and the Minderoo Foundation collaborate to study micro- and nanoplastics in human blood and tissue samples, in a contamination-controlled lab.

Queensland Alliance for Environmental Health Sciences (QAEHS) Director Professor Kevin Thomas said: “We know that humans are exposed to plastics daily, but we don’t know if nanoplastics are in our urine, body and brain and if they do harm.”

Little is known about nanoplastics in food webs and soil ecosystems or their uptake by soil organisms. Agricultural soil is potentially receiving nanoplastics from sources such as atmospheric deposition, irrigation with wastewater, application of sewage sludge for agricultural purposes, and use of mulching film. Measurement of uptake of nanoplastics from the soil by plants, particularly vegetables and fruit in agricultural soils, is a critical step to reveal whether and to what extent nanoplastics can make their way into edible plants and food webs.

In their study, researchers at the University of Eastern Finland developed a metallic fingerprint-based technique to detect and measure nanoplastics in organisms. Lettuce plants were exposed to nanoplastics for 14 days through contaminated soil. They were harvested and fed to insects for 5 days, and then the insects were fed to fish for another five days.

Using scanning electron microscopy, researchers analysed the dissected plants, insects and fish. The images showed that nanoplastics were taken up by the roots of the plants and accumulated in the leaves. Nanoplastics were then transferred from the contaminated lettuce to the insects. The imaging of the digestive system of the insects showed that both PS and PVC nanoplastics were present in the mouth and the gut even after emptying their guts for 24 hours.

The number of PS nanoplastics in the insects was significantly lower than the number of PVC nanoplastics, which is consistent with the lower number of PS particles in the lettuce. When the fish fed on the contaminated insects, particles were detected in the gills, liver and intestine tissues, while no particles were found in the brain tissue.

Image credit: iStock.com/ISMODE