Quantitative tracking of nanoplastics along the food chain from lettuce (Lactuca sativa) to snails (Cantareus aspersus)

Terrestrial systems are a significant sink for plastic contamination, including nano- and microplastics (NMPs). To date, limited information is available about the transfer of NMPs up the food web via trophic transfer, however, concerns about this exposure pathway for invertebrates and higher-level organisms have been raised. We aim to examine and quantify the trophic transfer of europium doped polystyrene nanoplastics (Eu-PS; NPs) within a terrestrial food chain. The uptake of 100 nm spherical Eu-PS particles from water through the roots of the plants to the leaves and finally to garden snails (Cantareus aspersus) was assessed. Lettuce (Lactuca sativa) was cultivated in Hoagland solution spiked with different concentrations of Eu-PS (15, 150 and 1500 μg/L) for three weeks. Then, lettuce shoots were used as food for snails for 19 days at a rate of 1 g of shoots per day. The Eu-PS primarily accumulated in the lettuce roots for all treatments, with a limited transfer to the shoots (only quantifiable in the highest treatment; translocation factor: TF < 1). No detectable levels of Eu-PS were found in the snails' digestive gland; however, the Eu-PS particles were detected in their feces (trophic transfer factor: TFF > 1). Moreover, only limited effects were observed on lettuce biomass by NPs treatments. No effects of the Eu-PS particles on snails were observed, with the exception of a consistent decrease in the shell diameter. Overall, our research illustrates that NPs can be absorbed by plants through their roots, subsequently transported to the shoots. However, our findings show limited transfer of NPs into snail tissues, but direct excretion into their feces. We provide an important insight into the potential transfer within the human food chain.