Tiny plastic particles are climbing up the food chain from the ground up

KUOPIO, Finland — Nanoplastics are making their way into our food, and likely accumulating in our bodies as a result, according to a recent study. Researchers from the University of Eastern Finland have created a fingerprint-based technique to detect tiny plastic particles in organisms. The method helped identify nanoplastics in the soil where lettuce grows.

Despite the usefulness of plastics, it is one of the hardest substances to recycle. If not broken down correctly, the plastic product can create microplastics and nanoplastics. These particles are toxic to plants, animals, and humans. However, not much is known about how plastic makes its way up the food chain, especially if they originally come from the soil. Nanoplastics enter the ground from a number of places, from atmospheric deposition, irrigation with wastewater, use of sewage sludge, and mulching film. Understanding how much nanoplastic is contaminating plant soil, especially where fruits and vegetables grow, can help farmers determine which plants are safe to eat.

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Researchers applied the metallic fingerprint-based technique to a model food chain with lettuce as the primary produce, black soldier fly larvae as a primary consumer, and insect-eating fish as the secondary consumer. The team used common nanoplastics found in the environment, such as polystyrene and polyvinyl chloride.

They exposed lettuce plants to nanoplastics for two weeks through contaminated soil. Study authors then harvested and fed the lettuce to black soldier fly larvae. After five days of eating the lettuce, researchers fed these insects to fish for another five days.

Using a microscope, the team studied the anatomy of the dissected plants, larvae, and fish. The imaging showed that the plant roots took in nanoplastics from the soil and stored them in their leaves. The nanoplastics then moved from the lettuce to the insects. Images from the insects’ digestive system showed that both types of nanoplastics remained in their mouths and guts — even after emptying the gut for 24 hours.

Nanoplastics then made their way from insects to the fish, with particles contaminating the gills, liver, and intestinal tissues. Study authors did not find any plastic particles in the brain, however.

“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 generalizable to other plants and crops and to field settings. However, further research into the topic is still urgently needed,” explains Dr. Fazel Monikh, a researcher at the University of Eastern Finland and lead author of the study, in a university release.

The study is published in the journal Nano Today.

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About the Author

Jocelyn Solis-Moreira

Jocelyn is a New York-based science journalist whose work has appeared in Discover Magazine, Health, and Live Science, among other publications. She holds a Master’s of Science in Psychology with a concentration in behavioral neuroscience and a Bachelor’s of Science in integrative neuroscience from Binghamton University. Jocelyn has reported on several medical and science topics ranging from coronavirus news to the latest findings in women’s health.

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