PlasticFADE: a predictive model for plastic fragmentation and degradation rates in the environment

Plastics are widespread across the globe, posing risks to environmental and human health. Fragmentation and degradation are key processes that govern the environmental fate and impacts of plastics, yet their rates remain poorly quantified. Life cycle assessment (LCA) is widely recognized as the standard framework for comprehensively evaluating the environmental performance of products and services. Accurately capturing the fate of plastics in natural environments therefore represents a critical priority for impact assessment modeling. However, the degradation and fragmentation mechanisms governing plastic polymer behavior remain poorly quantified in current life cycle impact assessment (LCIA) models, limiting their capacity to characterize the potential biodiversity impacts arising from plastic emissions to natural environments. In this study, experimental data on plastic fragmentation and degradation were systematically compiled from the literature. Using these data, PlasticFADE was developed as the first iteration of an empirical model to predict polymer-specific rate constants in various environmental compartments. The model predictions reveal that the rate constants vary considerably across polymers and compartments. Estimated lifespans of plastics range from several decades to over a millennium. Beaches are identified as hotspots for both fragmentation and degradation, whereas plastics are most likely to remain intact in the water column. Criteria are proposed for evaluating the reliability of the model outputs, which should be interpreted with due caution. Despite its limitations, the model offers valuable insights into plastic fate processes and offers significant potential for improving current LCIA methods for plastic emissions assessment.