Evaluation of phenotypic and behavioral toxicity of micro- and nano-plastic polystyrene particles in larval zebrafish (<i>Danio rerio</i>)

Plastic particles have been found in all environments and it is necessary to understand the risks these particles pose in, and to, the environment. The objectives of this work were to understand the toxic effects of varying size and concentration of polystyrene (PS) micro- and nano-plastics in zebrafish embryos and their fate within the larvae. In this work, larval zebrafish (Danio rerio) were exposed to six sizes (0.05, 0.25, 0.53, 2.1, 6.02, and 10.2 µm diameter) and concentrations (0.0005 to 0.2 µg/µL) of PS micro/nanoplastics particles. The zebrafish embryo toxicity (ZET) and the general and behavioral toxicity (GBT) assays were used to determine particle toxicity in embryos. Behavioral analysis was performed and micro/nanoplastics uptake and organ distribution were assessed. Phenotypic and behavioral toxicity was observed in all exposures with the exception of 0.25 µm particle-exposed larvae. Significant phenotypic toxicity was seen at the highest tested exposure concentration, with some sizes showing potential recovery as time increased in the assay. Behavioral analysis demonstrated a decrease in baseline activity across all micro- and nano-plastic sizes. Significant increases in light-dark responses were recorded in ZET assays of smaller-sized particles and no significant effects were observed at larger sizes. Significant decreases in this response were reported in the GBT assays of all tested sizes with the exception of the 0.05-µm particles. These assays demonstrate the general, developmental, and neurotoxicity of micro/nanoplastics to a model organism, which can be used to infer individual and population-level effects of exposure.