Microplastics as vectors for environmental contaminants: Exploring sorption, desorption, and transfer to biota

ABSTRACT The occurrence and effects of microplastics (MPs) in the aquatic environment are receiving increasing attention. In addition to their possible direct adverse effects on biota, the potential role of MPs as vectors for hydrophobic organic chemicals (HOCs), compared to natural pathways, is a topic of much debate. It is evident, however, that temporal and spatial variations of MP occurrence do (and will) occur. To further improve the estimations of the role of MPs as vectors for HOC transfer into biota under varying MP concentrations and environmental conditions, it is important to identify and understand the governing processes. Here, we explore HOC sorption to and desorption from MPs and the underlying principles for their interactions. We discuss intrinsic and extrinsic parameters influencing these processes and focus on the importance of the exposure route for diffusive mass transfer. Also, we outline research needed to fill knowledge gaps and improve model‐based calculations of MP‐facilitated HOC transfer in the environment. Integr Environ Assess Manag 2017;13:488–493. © 2017 SETAC Key Points Concentrations of microplastics (MPs) and environmental conditions change over time, meaning that spatio‐temporal hotspots do (and will) occur, potentially changing the relative importance of MPs as hydrophobic organic chemical (HOC) vectors compared to natural pathways (such as water, food, and natural particulate matter). An improved understanding of the governing processes is needed to better evaluate the role of MPs as pathways for HOC transfer into biota under such varying conditions. We point out future research needed and highlight direct contact exposure as a route of HOC transfer process, which should not be overlooked when working toward a better understanding and model‐based estimations of microplastic as HOC vectors in the environment.