Release of Additives and Non-Intentionally Added Substances from Microplastics Under Environmentally Relevant Conditions

Abstract

Microplastics and plastic additives are contaminants of emerging environmental concern. Knowledge on the extent and rate of additive leaching from microplastics is essential to understand their behaviour and fate in receiving environments and the risk they present to organisms. We evaluated additive leaching from a range of common polymer-additive formulations using an environmentally relevant dynamic leaching method. The method was validated to ensure sink conditions were maintained over the duration of the test, thereby avoiding solubility limited release and ensuring the test conditions were representative of those occurring in the environment. High-resolution liquid chromatography-mass spectrometry was used to quantify targeted plastic additives and identify non-intentionally added substances leaching from the plastics. Leaching profiles showed significantly different kinetics across the four plastics, with cumulative additive release over 64 d spanning more than five orders of magnitude from 0.0002% to 38%. Diffusion-controlled release of additives was observed for low density polyethylene, polyvinyl chloride and nylon 6. Monomers and oligomers of nylon 6 and polyethylene terephthalate were the predominant non-intentionally added substances released. This study highlights the wide variation in leaching behaviour of different plastics and the need for further studies on microplastic leaching using standardised and environmentally relevant methods.

Keywords: plastic pollution, Microplastic, plastic additive, leaching, release kinetics