Microplastic uptake and impacts on crops under realistic exposure: implications for soil-plant systems.

Increasing micro- and nanoplastic (MNP) contamination of agroecosystems has become a significant concern due to their potential effects on crops and food safety, yet their fate and effects under environmentally realistic conditions remain poorly understood. Here, we investigate the behaviour, toxicity and uptake of MNPs under realistic exposure conditions, considering polymer types, size, concentration and surface characteristics, in two crop plants: wheat (Triticum aestivum) and tomato (Solanum lycopersicum) in a silty loam soil, under both individual and mixed exposure. Plant presence significantly reduced the leaching of aged polyethylene terephthalate (PET) fibres and polyethylene (PE) fragments in soils, with smaller MPs (average 124 µm) leaching more than larger MPs (average 568 µm), implying a plant-mediated retention effect. Fibres caused greater effects than fragments, particularly in tomato, reducing chlorophyll content and plant growth. Notably, mixed MNP exposures induced more pronounced phytotoxicity in tomato than single exposures, suggesting potential synergistic effects. Although pristine NPs (∼400 nm) were not taken up, we found that aged NPs can be absorbed by plant and translocated to both roots and stem base tissue in both species, with further translocation to the leaf vascular system observed in tomato, highlighting the impact of surface characteristics on the uptake. This study provides new evidence on the effects and uptake of environmentally representative MNPs, addressing a critical gap in current research that mostly relies on pristine MNPs and at unrealistic concentrations. Our findings highlight the urgent need for risk assessments and regulatory frameworks that reflect real-world conditions to protect sustainable agriculture and public health.