Polyurethane microplastics and associated tris(chloropropyl)phosphate additives both affect development in larval fathead minnow Pimephales promelas.

Microplastics (< 5 mm) are a diverse class of contaminants ranging in morphology, polymer type, and chemical cocktail. Microplastic toxicity can be driven by one or a combination of these characteristics. Most studies, however, evaluate the physical effect of the most commercially available polymers. By disregarding other polymers with high consumption and/or production rates, and the chemical constituents of plastics, we fail to have a holistic understanding of the mechanisms of toxicity. Polyurethane is understudied in terms of effects testing yet considered one of the most hazardous polymers due to its chemical composition. Polyurethane is a high production polymer and is found in common consumer products ranging from packaging to spray foam insulation. To better understand the physico-chemical effects of polyurethane and a common additive in polyurethane products, we exposed larval fathead minnows for 28 days to polyurethane without chemical additives (i.e., plastic treatment), chemical leachate from polyurethane containing chemical additives (i.e., tris(chloropropyl)phosphate [TCPP]; i.e., chemical treatment) and polyurethane with chemical additives (i.e., plastic with chemical treatment) in a fully factorial experiment. We observed significant decreases in growth at 12 days posthatch (dph) in the plastic, chemical, and plastic with chemical treatments, suggesting a physical and chemical driver of toxicity. At 28 dph, we did not observe significant differences in growth, suggesting individuals can recover. We also observed concentrations of ΣTCPPs in fathead minnow exposed to the plastic with chemical treatment and the chemical only treatment, demonstrating TCPP uptake in exposed individuals. Combined, our data suggests the importance of both the physical and chemical components of microplastics when assessing effects, and thus emphasizing the need to evaluate the effects of microplastics in a multidimensional way.