A 2‐Tier standard method to test the toxicity of microplastics in marine water using Paracentrotus lividu s and Acartia clausi larvae

A 2‐tier standardized protocol was designed to test the toxicity of microplastics to planktonic organisms. This approach uses sea urchin ( Paracentrotus lividus ) and copepod ( Acartia clausi ) larvae because they are common biological models in marine research, and standard methods for toxicity testing with regulatory applications are available. In Tier I, leachates obtained at a 100 to 1 liquid to solid ratio are tested, and toxic units are calculated using a probit dose–response model to quantify the toxicity of the plastics. In Tier II, which is conducted only if significant toxicity (> 1 toxic unit) is found in Tier I, particles less than 20 μm in size are tested at concentrations between 0.1 and 10 mg L −1 , and a toxicity threshold suitable for ranking materials according to their toxicity is obtained from the 10% effect concentration (EC10) values. Results point to chemical additives as being responsible for the toxicity found in certain plastic materials. This process is suitable for both a priori identification of the hazard posed by plastic objects in the aquatic environment, and a posteriori assessment of environmental risk caused by microplastic pollution. The method also provides a quantitative procedure appropriate for ranking plastic materials according to their toxicity to aquatic organisms. Environ Toxicol Chem 2019;38:630–637. © 2018 SETAC