Addressing the importance of microplastic particles as vectors for long-range transport of chemical contaminants: perspective in relation to prioritizing research and regulatory actions

Over the last several years there has been increasing concern regarding the environmental fate and potential global transport of plastic debris, particularly in the form of microplastic particles (MPs). The global transport of MPs has also triggered concerns regarding the potential role that its mobility may represent towards influencing the long-range environmental transport (LRET) of particle-bound chemicals, particularly the large number of chemicals known to be added to plastic. This perspective considers the various lines-of-evidence that might be used towards understanding the LRET of persistent organic pollutants (POPs). For instance, it has been proposed that the LRET of POPs is facilitated by global fractionation processes that facilitate the mobility of chemicals from source regions towards remote locations, such as the polar regions, where they have the potential to accumulate. These processes are influenced by the physicochemical properties of POPs and can result in various transport mechanisms influencing environmental fate and transport. Here I suggest that there are similarities that can be drawn, whereby knowledge of how differences in the physicochemical properties of MPs relative to different emission scenarios, can influence the relative importance of sequestration processes that may result in global fractionation of MPs. Several challenges are identified throughout the perspective, with an urgent need towards the development and application of standard sampling and analytical methods being identified as critical for enabling datasets to be reliably compared for use in better understanding potential source-receptor relationships, as well as advancing the characterization and quantification of various environmental fate processes. In many instances, it is suggested that advances in our understanding can be facilitated based on knowledge obtained in other areas of research, such as in relation to studies developing tools to evaluate the mobility of particulate organic matter in aqueous environments or from studies investigating the fate and mobility of atmospheric particulates. Recognizing that not all MPs are equal, with respect to environmental fate and toxicological effects, knowledge regarding which types of MPs are likely to be subject to LRET can only strengthen our ability to evaluate their role as vectors of transport for plastic associated chemicals and the associated risks that their LRET may represent. Nevertheless, several outstanding issues remain that would benefit from constructive discussions between all stakeholders. It is anticipated that this perspective can play a role in initiating those discussions.