Potential human health risk of the emerging environmental contaminant 6-PPD quinone

The tire antioxidant 6-PPD has been widely used to enhance tire performance and extend tire lifespan. 6-PPD quinone (6-PPDQ), a quinone derivative derived from 6-PPD in the presence of ozone, has been recognized an emerging environmental contaminant. In addition to causing acute lethality to coho salmon, 6-PPDQ exhibits toxic effects on other aquatic species and mammals. Based on the existing evidence, we provide a critical overview on the human internal exposure, potential adverse effects on health, and prediction of human health risk of 6-PPDQ. 6-PPDQ could be detected in human samples, including human urine, blood, and cerebrospinal fluid. Human exposure to 6-PPDQ in the environment is inevitable and may lead to adverse health effects, including hepatotoxicity, enterotoxicity, pulmonary toxicity, neurotoxicity, reproductive toxicity, and cardiotoxicity. Additionally, potential human health risk to 6-PPDQ through exposure routes and human samples were predicted. This review is helpful to identify the existing knowledge gaps and future research directions regarding the human health effects of 6-PPDQ.