Impact Assessment of Microplastic Emissions in LCA: Preliminary Characterization Factors for Expanded Polystyrene and Tire and Road Wear Particles

Although life cycle assessment (LCA) includes a variety of potential environmental impacts (climate change, ecotoxicity, etc.), to date there is no LCA methodology to include the potential impacts of plastic litter. This limits the applicability of LCA as a tool to compare potential impacts of single-use plastics and their alternatives. To address this shortcoming of LCA, the international scientific work group MarILCA (MARine Impacts in LCA) was founded in 2018 with the goal to propose a methodology for assessing (macro-, micro, nano-) plastic litter impacts (marilca.org). Within the MarILCA framework, the new impact category physical effects on biota addresses impacts associated with physical effects of plastics such as entanglement (of macroplastics) or ingestion (of microplastics), which ultimately may affect ecosystem quality. This work proposes two examples of preliminary characterization factors (CFs) for assessing potential impacts of microplastic emissions in aquatic environments via the impact category physical effects on biota. To develop these CFs, effect factors for assessing the potential impacts of micro- and nanoplastics on aquatic environments proposed by Lavoie et al. (2021) were used. To complete the preliminary CF modelling, simplified fate factors are developed for two types of microplastics: expanded polystyrene (EPS) and tire and road wear particles (TRWP). This exploratory work aims at understanding the relevance of different transport and removal mechanisms influencing the fate of microplastics in aquatic environment, identify challenges and guide research efforts. For EPS and TRWP, this work tested different fate scenarios for the degradation and sedimentation of microplastics. The fate scenarios were based on literature values and expert estimations. The obtained simplified fate factors were integrated into preliminary CFs and applied to a food container case study. The results confirm the potential relevance of marine litter impacts, the need for developing physical effects on biota CFs specific to different types of plastics, as well as the importance of modelling the fate of microplastics in more detail to reduce the uncertainty of CFs.