Adverse effects of 6PPD-quinone bioaccumulation at environmentally relevant concentrations on Cyprinus carpio growth and development.

With industrial advancements, the development and use of various additive substances have increased, leading to their potential release into the environment during use and disposal. As a primary tyre additive, the rubber additive, N1-(4-methylpentan-2-yl)-N4-phenylbenzene-1,4-diamine (6PPD) has recently become an environmental issue. Its oxidation by-product, 6PPD-quinone (6PPD-Q), which is released from tyre wear, has drawn considerable attention because of its potent toxicity to fish in aquatic environments, particularly to coho salmon. In this study, we aimed to determine whether 6PPD-Q is potentially toxic to non-salmonid fish species within aquatic ecosystems, using carp (Cyprinus carpio) as a representative model organism for toxicity assessment. We analysed the proteomic changes in carp following 8 weeks of chronic exposure to 6PPD-Q, and the effects were further evaluated using gene-based analyses. 6PPD-Q disrupts cytoskeleton-related pathways and induces oxidative stress in carp. This can potentially impair the antioxidant defence system and suppress gene expression related to growth and metabolism, contributing to a decline in health. These findings suggest that 6PPD-Q poses a serious threat to the growth and survival of aquatic organisms. Considering the escalating global tyre consumption and the resultant environmental runoff of 6PPD and 6PPD-Q, ongoing research into the ecotoxicology of these additives, along with the development of safer alternatives, is strongly warranted.