Additional file 1: Table S1. Overview of ranges and mean or median values (underlined) of concentrations of microplastics (or, where specified, small plastic particles) in the marine environment based on Hidalgo-Ruz et al. [11] and selected recent publication. Table S2. Overview of ranges and mean or median values (underlined) of concentrations of microplastics (or, where specified, small plastic particles) in the freshwater environment. Table S3. Overview of effect concentrations derived in ecotoxicity tests with aquatic organisms exposed to microplastics