Further studies in translatable model systems are needed to predict the impacts of human microplastic exposure

Microplastics are a pervasive environmental contaminant that have been found in many media including water sources, soils, and foodstuff. Due to the worldwide presence and persistence of microplastic debris, human exposure is inevitable. Human exposure occurs predominantly through ingestion, although dermal and inhalation exposures are probable. Microplastic single exposure studies in aquatic species and fish have shown various toxic effects including those on reproduction and survival. In addition to potential intrinsic toxicity, microplastics often have chemicals adsorbed to their surfaces. Studies report that these chemicals can have innate toxicity that is modulated by the composition of microplastics. Both the impacts of microplastics alone and co-exposures with adsorbed chemicals exhibit size dependent effects. Analysis of the current literature has revealed published studies predominantly investigate the toxicity of microplastic exposure in fish and other aquatic species, with limited knowledge about the effects in mammals and cell lines. Toxicity has been shown to vary widely between taxonomic groups, suggesting inferring human health relevance will require model systems where human routes of exposure can be mimicked. Although it may be difficult to extrapolate the results from aquatic model systems to relevant human health impacts, they may suggest effects to investigate. In order to best estimate the short- and long-term impacts of human microplastic exposure, it is imperative that studies in model systems with increased similarity to human anatomy and cellular processes be done.