MPsizeBase: a database for particle size distributed environmental microplastic data

Understanding the sources, dispersion, and health impacts of microplastic (MP) pollution requires quantitative observations in terms of MP number and/or mass concentrations. Measurements of environmental MP fragments or fibers typically target variable size spans within the formal 1 to 5000 µm range, due to different sampling and detection techniques, and are therefore not directly comparable. In addition, the majority of measurements by microscopy techniques are number based, whereas life cycle analysis, numerical models for MP dispersion and policy evaluation, and plastic additive exposure estimates are mass based. Data analysis frameworks, based on measured MP particle number size distribution (PSD), have been developed to align and extrapolate measurements to a common MP size range (e.g. 1-5000 or 1-300 µm), which in turn allows direct data inter-comparison. In this study we present the MPsizeBase, a database of published MP number concentrations and PSD in the environment, including land, ocean and atmosphere. MPsizeBase uses the power law to fit observed MP cumulative number PSDs, and extrapolate and align observations over a common size range of choice. Assuming MP shape and volume approximations, MPsizeBase also estimates size-aligned MP mass concentrations. We illustrate how the MPsizeBase can be used for inter-comparison studies, and end with recommendations on MP size, shape, and PSD reporting, including length, width and surface area. We invite scientists to contribute old and new data to MPsizeBase for additional environmental compartments, including soils, sediment and biota.