A Critical Review of Microplastic Contamination in Agricultural Soils and its Potential Risks to Crops and Human Health

Microplastic contamination of agricultural soils has moved from a largely conceptual concern to an empirically documented component of terrestrial pollution. Agricultural plastic films, sewage sludge, compost and other organic amendments, irrigation water, atmospheric deposition, and diffuse litter can introduce plastic particles to soil, while tillage, weathering, bioturbation, and water movement redistribute and fragment them. This critical narrative review evaluates evidence on the occurrence and persistence of microplastics in agricultural soils, consequences for soil function and biota, uptake and toxicity in crops, transfer to edible tissues, and implications for human health. Literature published from 1 January 2012 to 17 July 2026 was identified through multidisciplinary and agriculture-, environmental-, and health-oriented scholarly sources and appraised for analytical validity, environmental realism, study design, and claim-source alignment. Field studies provide convincing evidence that repeated plastic mulching and sludge application can increase soil contamination, but cross-study abundance estimates remain poorly comparable because particle-size windows, extraction efficiencies, polymer identification, and reporting units differ. Controlled experiments show that microplastics can alter aggregation, porosity, water relations, microbial activity, soil fauna, plant growth, nutrient acquisition, photosynthesis, and oxidative balance; nevertheless, effect direction depends strongly on polymer, shape, size, concentration, soil, and crop. Evidence for true plant internalisation is strongest for nanoplastics and submicrometre particles, especially in controlled systems, whereas field-scale transfer of larger microplastics into edible tissues remains uncertain. Human biomonitoring demonstrates exposure to plastic particles through multiple routes, and emerging observational data raise legitimate health concerns, but no study has established a causal pathway from contaminated agricultural soil through crops to a defined human disease outcome. The most defensible risk interpretation is therefore pathway-specific: agricultural soil contamination is established, crop effects are plausible and increasingly supported, food-chain transfer is demonstrated under selected conditions, and human health risk from the soil-crop route remains insufficiently quantified. Progress depends on harmonised analytical methods, realistic field exposures, quantitative crop-transfer studies, and route-resolved human exposure assessment.