Ecotoxicity testing of microplastics: Considering the heterogeneity of physicochemical properties

Abstract

“Microplastic” is an umbrella term that covers many particle shapes, sizes, and polymer types, and as such the physical and chemical properties of environmental microplastics will differ from the primary microbeads commonly used for ecotoxicity testing. In the present article, we discuss the physical and chemical properties of microplastics that are potentially relevant to their ecotoxicity, including particle size, particle shape, crystallinity, surface chemistry, and polymer and additive composition. Overall, there is a need for a structured approach to the testing of different properties to identify which are the most relevant drivers of microplastic toxicity. In addition, the properties discussed will be influenced by and change depending on environmental conditions and degradation pathways. Future challenges include new technologies that will enter the plastic production cycle and the impact of these changes on the composition of environmental microplastics. Integr Environ Assess Manag 2017;13:470–475. © 2017 SETAC Key Points: In this commentary piece, we discuss the following aspects important for the hazard characterization of microplastics: 1) physical properties, including particle size, particle shape, surface area, and crystallinity; 2) chemical properties, including polymer type, additives compounds, and changes to surface properties; and 3) future innovations for the plastics industry, including new polymer types and the introduction of nanomaterials.