Polystyrene microplastics alter the toxicity of 6PPD to zebrafish (Danio rerio) larvae

Tire wear particles (TWPs) are a significant source of microplastics (MPs) and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) in aquatic environments. However, the combined toxicity of MPs and 6PPD to aquatic organisms remains unclear. Here, we investigated the bioaccumulation of 6PPD, developmental toxicity, oxidative stress, and metabolic alterations in zebrafish larvae following single and combined exposure to polystyrene MPs (PSMPs) and 6PPD. Our results indicated that co-exposure to PSMPs and 6PPD induced synergistic toxicity in zebrafish larvae, significantly elevating levels of reactive oxygen species (ROS) and malondialdehyde (MDA), along with enhancing antioxidant enzyme activities. PSMPs did not influence the bioaccumulation of 6PPD, but increased the concentration of 6PPD quinone (6PPD-Q) in zebrafish larvae. PSMPs and 6PPD altered the metabolomic profiles of zebrafish larvae, affecting organic acids and their derivatives, amino acids and carbohydrates. The primary distinctions between single and combined exposures were observed in organic acids (citric acid and 9-Octadecenoic acid), sugars (D-Allose, D-Arabinose, and d-Mannose), and cholesterol. These findings imply PSMPs alter the toxicity of 6PPD to zebrafish larvae, providing valuable data for assessing the potential risks of single and combined pollution of MPs and 6PPD to aquatic creatures.