Updated and comprehensive characterization factors for microplastics in life cycle assessment considering multimedia fate modelling

Plastic litter poses potentially significant threats to ecosystem quality, human health, and socio-economic assets. However, current Life Cycle Assessment (LCA) does not properly consider these impacts. The international research group MarILCA has proposed a framework to include plastic litter impacts in LCA, highlighting the interdependence of environmental compartments and the importance of studying microplastic transfers between them. While MarILCA has presently focused on marine impacts, this project aims to investigate the impacts of microplastic emissions in other compartments by calculating multimedia Characterization Factors (CF) for the impact category: physical effects on biota. A fate model is developed building on the SimpleBox4Plastics model and adapted to the USEtox methodology. It covers nine environmental compartments on continental and global scales and illustrates the fate mechanisms of microplastics within and between the compartments, from emission to removal. Fate Factors (FF) are computed for 13 spherical polymers in 5 sizes, quantifying the distribution and residence time of plastic emissions in the compartments. Subsequently, CFs are calculated using exposure-effect factors (EEF) for aquatic, terrestrial, and sedimentary ecosystems. Preliminary findings suggest that the highest CFs concern marine ecosystems for a direct emission into sea water or its sediments (i.e. from macroplastic fragmenting), or emission into freshwater for low-density polymers, as a large proportion of microplastics emitted there end up in the sea. High CFs are also noted for aquatic ecosystems when low-density polymers are emitted into lakes, where they tend to remain. The lowest CFs are those for terrestrial ecosystems which can be explained by a lower EEF in soil. This model allows for the first time the integration of potential impacts of microplastics in LCA, in all compartments. The CFs can be integrated with emission inventories, enhancing LCAs of plastic products and empowering governments and consumers to make better-informed decisions regarding plastic use.

Mots clés

• LCA
• modelling
• impact
• fate
• characterization factors
• microplastics
• ecosystems
• soil
• sea
• freshwater