Transport of persistent organic pollutants: Another effect of microplastic pollution?

Over the past decade, the number of studies examining the presence and effects of microplastics in the environment has drastically increased. Works seeking to identify these particles have proven beyond doubt that microplastics constitute a generalized pollution affecting all environmental compartments, from inside air to arctic snows. Studies on their potential ecotoxicological impacts were more nuanced but many have shown deleterious effects when these microplastics were associated with persistent organic pollutants. This primer mainly focuses on POP sorption and transport by microplastics in the aquatic environment and the possible toxic effects that result from it. Indeed, the associations between microplastics and persistent organic pollutants are very common in the environment. If the mechanisms of interactions are well known, they depend on many factors and their significance in the environment can be very variable in time and space. Indeed, these interactions depend on both the plastic particle (polymer type, crystallinity, particle size, shape, specific area, and functional groups/polarity) and the pollutant (hydrophobicity, functional groups) but also environmental factors (microorganism population, salinity/ionic strength, pH, dissolved organic matter concentration, and temperature). Changes in the interactions between pollutants and microplastics can result in pollutant release in the aquatic environment and potential toxic effects. However, apart from specific situations, the role of microplastics as local source of exogenous molecules (PAHs, PCBs, etc.) is rarely significant because the limited amounts of involved pollutants. It is much less negligible for endogenous chemicals that enter into the initial composition of the plastic (phthalates, biocides, etc.).