Plastic pollution and microplastics are prevalent across the globe and have been highlighted as a contaminant class of environmental concern. However, the extent and mechanism by which plastic pollution affects organisms is not well understood. One proposed mechanism through which plastics may exert harm is the leaching of plastic additives, such as UV stabilisers, colourants, and plasticisers. To establish the risk of microplastic pollution the behaviour and fate of additives in receiving environments must be characterised.
We present an assessment of additive fate in microplastic pollution, using both laboratory and field-based experiments. Additive leaching kinetics were determined for three common plastics (polyethylene, polyethylene terephthalate, and nylon 6) prepared with and without exposure to artificial weathering. Targeted and non-targeted analysis was performed using high-resolution liquid chromatography-mass spectrometry. Additive leaching under laboratory conditions was significantly different across the three plastics, with cumulative additive release spanning more than five orders of magnitude over a 64-day test period. The impact of accelerated weathering on leaching kinetics was highly dependent upon the polymer type, additive chemistry, and weathering exposure. Field-based marine leaching experiments were consistent with laboratory findings, where additive fate was strongly dependent upon polymer type, additives, and exposure to weathering. Few differences were observed between geographic locations used for deployment. Non-target analysis revealed a distinct extractables profile for each plastic. The extractables profile was strongly influenced by exposure to accelerated weathering, with deployment time and location provoking minimal change. This work highlights the importance of knowing what additives are incorporated into plastic products and understanding the fate of additives in receiving environments for meaningful risk assessment.