Integrating the Environmental Fate and Systemic Ecotoxicity of Soil Micro-/Nanoplastics into Life Cycle Assessment: A Critical Review

Soil micro-/nanoplastics (MNPs) have emerged as critical terrestrial pollutants, especially in intensively managed agricultural systems. Yet conventional life cycle assessment (LCA) still underestimates the environmental burden of plastics because MNPs emissions, fate, and long-term ecotoxicity are rarely represented in either life cycle inventory (LCI) or life cycle impact assessment (LCIA). This critical review synthesizes the transformation, transport, aging, and ecological effects of soil MNPs and, more importantly, examines where current attempts to integrate them into LCA remain methodologically weak. Rather than proposing universal default thresholds or one mandatory release model, the review identifies three unresolved bottlenecks: how soil MNPs impacts should be positioned relative to standalone ecotoxicity, broader soil-degradation endpoints, and delayed freshwater transfer; how fate and effect terms can be derived when available evidence is still dominated by short-term laboratory tests on pristine particles; and how dynamic release from residual films can be represented without overstating precision. Accordingly, we propose a cautious soil-oriented implementation scaffold in which dynamic inventories, soil-specific fate-exposure-effect logic, minimum reporting requirements, and explicit scenario recommendations are treated as reporting expectations rather than as fully standardized defaults. An illustrative mulch-film example is used only to demonstrate bookkeeping logic, sensitivity priorities, and minimum reporting needs; it is not used to claim a universal ranking between polyethylene (PE) and biodegradable mulch films (BDMs). The review further argues that soil ecotoxicity alone is insufficient: parallel modules or explicitly declared omissions are also needed for soil-structure degradation, soil-organic-carbon loss, and secondary greenhouse-gas release. Overall, an MNPs-corrected LCA should therefore be viewed not as a mature method, but as a critical next step for improving plastic-footprint accounting, comparative product assessment, and soil-protection policy.