Toxicity of microplastic fibers containing azobenzene disperse dyes to human lung epithelial cells cultured at an air-liquid interface

There is growing concern surrounding the human health effects following inhalation exposure to microplastic fibers (MPFs). MPFs can harbor chemical additives, such as azobenzene disperse dyes (ADDs), that may contribute to their toxicity. The goal of this study was to determine the acute biological effects of dyed polyethylene terephthalate MPFs to fully differentiated normal human bronchial epithelial (NHBE) cells cultured at an air-liquid interface. Cells were exposed to 2000 undyed MPFs (84.80 µg/cm²) or 2000 dyed MPFs (129.86 µg/cm²) colored with a black dye stuff containing the dye Disperse Violet 93 (DV93) using a mesh hopper delivery device. Cells were also exposed to DV93 only (1 µg/mL). Results show that the dyed MPFs caused a more pronounced decrease in cell viability and transepithelial electrical resistance compared to undyed MPFs and unexposed control cells. Additionally, the DV93 and dyed MPFs significantly upregulated the mRNA expression of CYP1A1 and CYP1B1, which was not observed in the undyed MPF group. These results support the idea that components of MPFs, specifically azobenzene disperse dyes, can leach from MPFs in biological systems and exert unique toxicity profiles. This study emphasizes the importance of considering toxicity associated with both the fibers themselves and chemical leachates in future studies.