Microplastics as vectors of pharmaceuticals in aquatic organisms – An overview of their environmental implications

Microplastics (MPs) have been recognized as an environmental threat due to their persistence, ubiquity, and toxicity potential. Due to their small size, MPs are endowed with a large specific surface area, having the ability to sorb and accumulate other contaminants that co-exist with them in the aquatic environment as it is the case of pharmaceuticals. In this way, MPs can act as vectors, facilitating the contact of pharmaceuticals with aquatic organisms. Once ingested, MPs may desorb pharmaceuticals, increasing their bioavailability, which could promote their bioaccumulation and biomagnification through the food web as well as modulate their toxic effects. Microplastics may differently impact the toxicity of pharmaceuticals by potentiating (synergism) or decreasing (antagonism) it. This review aims at highlighting the role of MPs as vectors of pharmaceuticals to aquatic organisms and how the interaction of these emerging contaminants may influence the bioaccumulation and toxicity of pharmaceuticals on biota. Examples of different scenarios resulting from the exposure of aquatic life to MPs and pharmaceuticals are presented. Future studies should cover a broader range of polymer types and environmental realistic concentrations to better understand the impact of MPs on the bioaccumulation and toxicity of pharmaceuticals.