Abstract

Microplastics (MPs) and nanoplastics (NPs) are pervasive contaminants in agricultural soils, raising concerns over their environmental fate, food chain infiltration, and potential human health impacts. This review critically examines their primary sources—plastic mulching, biosolids, organic fertilisers, and atmospheric deposition—while distinguishing findings from laboratory, semi-field, and field studies. We assess their effects on soil health, microbial diversity, and crop productivity, emphasising methodological challenges in detecting and quantifying MPs. Plant and soil toxicity studies often use exaggerated MP concentrations (up to 50% by volume), whereas field data indicate much lower yet cumulatively significant levels (typically below 0.1% w/w). This discrepancy reveals the potential for long-term accumulative ecological risks and misrepresentations in many toxicity studies. Accurate toxicity assessments and analytical methodologies are crucial, as exaggerated MP concentrations in studies may misrepresent real-world risks. The review also evaluates plant uptake pathways, exploring bioaccumulation evidence and research discrepancies. In addition, we highlight the role of MPs as carriers of hazardous additives and pollutants, distinguishing their intrinsic effects from those of associated chemicals. A significant gap remains in standardised risk assessments and regulatory frameworks, limiting effective governance despite increasing environmental exposure. We propose future research priorities, including improved detection methods, long-term field studies, environmentally relevant toxicity studies and policy interventions, to mitigate the risks MPs and NPs pose in soil-based food systems. This review highlights the urgent need for coordinated scientific and regulatory efforts to address the growing challenges of agricultural plastic contamination.