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Microplastic contamination from agricultural plastic waste: Soil microbiome disruption and cascading food chain risks-A systematic review
Summary
The plastic used in farming (mulch films, greenhouse covers, etc.) breaks down into tiny microplastic particles that build up in soil, and this review of over 130 studies shows these particles harm the beneficial bacteria soil needs to stay healthy and cycle nutrients properly. Even more concerning, researchers found these microplastics turning up in common foods like rice, wheat, leafy greens, milk, and meat—meaning what starts as plastic waste in a farm field may end up on your dinner plate. The review calls for more research and stronger regulations, since we still don't fully understand the health risks of eating these particles
Global agricultural systems consume an estimated 12.5-15.7 million tonnes of plastic annually across mulch films, drip irrigation systems, greenhouse covers, silage wraps, and seed coatings. A significant fraction of this plastic undergoes physical degradation, UV photolysis, and biological fragmentation in situ, releasing microplastics (MPs; < 5 mm) and nanoplastics (< 1 µm) directly into agricultural soil environments. This systematic review synthesizes evidence from over 130 peer-reviewed publications (2010-2024) sourced exclusively from Q1 journals to comprehensively characterize: (i) the nature, quantity, and weathering mechanisms of agricultural plastic MP generation; (ii) the disruption of soil microbial community structure, diversity, and function - encompassing nitrogen cycling, carbon turnover, and enzymatic activity; (iii) MP uptake pathways in crop plants and the cascading contamination of food chains from soil to human dietary exposure; (iv) the synergistic ecotoxicology of MP-associated chemical additives (plasticizers, stabilizers, flame retardants); and (v) emerging mitigation strategies and critical regulatory gaps. Meta-analytical synthesis of 47 controlled experiments demonstrates that MP concentrations above 500 mg/kg soil consistently reduce bacterial Shannon diversity by 12-28%, suppress nitrification rates by 20-45%, and increase N₂O efflux by 35-65%. Food chain tracing studies confirm MP presence in rice, wheat, leafy vegetables, milk, and meat at concentrations posing emerging human health risks. The review identifies nano-MP soil toxicology, biodegradable plastic MP characterization, and food chain transfer quantification as the highest-priority research frontiers, and proposes a harmonized global regulatory framework for agricultural MP thresholds.