Nanoplastics are taken up by lettuce and barley under realistic soil condition

Nanoplastics (NPs) have been shown to be taken up by plants, raising concerns about their transfer into food webs and potential risks to human health. However, most existing studies have been conducted in hydroponic systems, which hardly represent realistic soil conditions and/or used fluorescent NPs, that do not allow for exact quantification. To quantify NP uptake and translocation by different crops under environmentally realistic conditions, ¹⁴C-labelled polystyrene NPs (~25 nm) were applied to intact soil monoliths at an environmental realistic concentration of 0.03% in the topsoil (0–10 cm). Winter barley (Hordeum vulgare) and lettuce (Lactuca sativa) were grown in spiked and unspiked monoliths; and plant samples were collected after five and nine weeks. Radioactivity in plants was quantified using liquid scintillation counting, additionally NP leaching through the soil columns was assessed.

After five weeks, lettuce had taken up an average of 8.9 µg NP g^-1 dry matter (DM), while winter barley accumulated 1.5 µg NP g^-1 DM, corresponding to approximately 0.02‰ and 0.004‰ of the applied NP, respectively. After nine weeks, lettuce accumulated on average 2.5 µg NP g^-1 DM and barley 2.0 µg NP g^-1 DM, corresponding to 0.026‰ and 0.014‰ of the applied NP, respectively. Detectable radioactivity in the soil percolates further indicating NP transport through the soil profile.

These findings demonstrate that NPs can be taken up and translocated by plants under realistic soil conditions and accumulate in edible tissues, highlighting a potential pathway for entry into the food chain.