Microplastics as a vector of arsenic contamination

The presence of microplastics (MPs) in environmental compartments is an issue of concern due to their moderate toxicity to organisms. This toxicity may increase if they adsorb dangerous pollutants, such as arsenic (As), a toxic metalloid threatening ecosystems and human health. The results of a review on this topic indicated that the abundance of As adsorbed on environmentally exposed MPs varied from non-detected values to 6.53 mg/kg. Nevertheless, this abundance was lower than that of other trace elements. This may be related to the contrasting mechanisms controlling adsorption. Unlike metal cations, aqueous As is in the form of neutral and anionic species, which may interact repulsively with MP-negative surfaces and MP electron-rich groups, inhibiting the As adsorption. This review highlights the scarcity of risk assessment studies on As adsorbed onto MPs. However, As–MP co-exposure effects such as decreasing biomass and alteration of metabolic processes in plants have been reported.