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

Abstract

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.

Risk assessment of microplastic particles

“…First, most empirical studies considered chemical exposure only through ingestion of microplastics, neglecting parallel uptake pathways. This overestimates the relative importance of microplastics as a vector for transport and uptake, but underestimates the total exposure to chemicals 15,35 . When all uptake processes are taken into account, uptake through microplastic ingestion is seen to be minor 15,41,187 .…”

“…Scientists often portray environmental microplastic as a diverse and complex material, given its origins from a wide variety of materials and products 1,2,4,8,9,29 , and define it simply as 'all plastic particles smaller than 5 mm' . Because this definition is vague, microplastic constitutes a heterogeneous mixture of polymers, sizes and shapes, and is associated with all kinds of chemicals 1,4,8,10,17,29,34,35 . For instance, polybrominated diphenyl ethers (PBDEs), phthalates, nonylphenols (NPs), bisphenol A (BPA) and antioxidants, all common additives in plastic products, slowly desorb into the environment when plastic items age and fragment 36 .…”

“…Microplastics can cause physical damage by adsorbing and aggregating on the surface of microalgae 128 , restrict movement by accumulating in tentacles 130 , or promote satiation and reduce food assimilation by blocking the food passage 121,[133][134][135]137,139,141,143,144,147 . Other studies have attributed the effects to specific plastic properties, such as the surface groups 28,31,35,36,135,138,142,143 , or the leaching of toxic chemicals from the microplastics 136,140,145,147 . The severity of the effects vary depending on the properties of the microplastics, their concentrations and the exposure time.…”

“…These terms are imprecise because phase distribution ensures that the same chemicals are also present in other environmental media or particles, such as soil, sediment, water, organic particles, algae, black carbon or detritus 15,17,35,37,38,41,85,100,102,103 . Depending on exposure concentrations, any of these chemicals from any such media can pose a risk to biota.…”

Implications of COVID-19 pandemic on environmental compartments: Is plastic pollution a major issue?

“…Thus, frequent ingestion of PPE litter can decrease organisms health due to physical effects and potential chemical body-burdens, as observed in Seagulls ( Seif et al, 2018 ). Although the fraction of hazardous chemicals (e.g., hydrophobic organics) sorbed by plastic debris seems to be low compared to natural particles, particularly in aquatic environments (see ( Koelmans et al, 2016 )); their role as vectors increases when its higher mobility is considered, contributing to long-range environmental transport and affect remote locations ( Gouin, 2021 ).

Figure 1 Source, fate, and effects of personal protective equipment in aquatic and terrestrial environments.

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