Physical properties of microplastics affecting the aquatic biota: A review

The physical properties of microplastics, such as size, type, polymer and chemical composition, affect their level of toxicity once ingested by aquatic species. Therefore, to be able to produce environmental relevant ecotoxicity data, laboratory tests should take these properties into consideration as well as in the calculation of effect factors for the Life Cycle Assessment methodology. In this study, we reviewed papers estimating ecotoxicity of microplastics ingested by species under laboratory conditions as well as data on microplastics ingested by species sampled from the field. This aims to identify the physical property of the plastics ingested and the influence on levels of ecotoxicity. Afterwards, our paper shows a mismatch between the physical properties ingested by the species sampled in the field and those tested for toxicity in laboratory studies. Regarding types, laboratory studies commonly expose aquatic species to regularly shaped particles such as microbeads and pellets (representing 72 %). For effect factors in LCA context, microbeads represent 88 % in number of datapoints. In contrast to this, irregularly shaped particles (e.g. fibres and fragments) are more frequently reported in the field, representing 85 % of the ingested microplastics. At the same time, regarding size, most of the laboratory studies examine microplastics and there is a lack of toxicity data for nano sized particles. A mismatch is also reported on the polymers; Polypropylene, Polyethylene and Polyester represented a total of 45 % of the samples detected in the field, while Polyethylene and Polystyrene represent 69 % in ecotoxicity studies and 78 % in effect factors. These mismatches shows that physical properties prevalent ingested by the species still lack data on levels of ecotoxicity as well as in number of data points in the LCA context.