Unveiling the mammalian cell cytotoxicity of tyre-impacted water in disinfection

Tyre-related chemicals, which enter the aquatic environment through surface runoff, are of growing concern owing to their high ecotoxicity and ubiquitous occurrence. However, their toxicological effects in drinking water remain unknown. Here, using Chinese hamster ovary cell cytotoxicity as the metric, we found that chloramine, chlorine and ozone disinfection substantially elevated the cytotoxicity of tyre-impacted water (5.0-, 4.0- and 1.4-fold increases, respectively). These were 3.1–6.0 times as high as disinfected pristine lake waters. Toxicity correlates with halogenated (especially brominated and iodinated) products formed from reactions between additives and disinfectants based on non-target analysis. Thirty-three chemicals (for example, benzothiazoles, phenols, benzophenones and arylamines) accounting for <5% of total carbon mass and their transformation products contributed to 25–36% of the cytotoxicity of disinfected tyre-impacted water. The cytotoxicity of drinking water could be substantially elevated in extreme precipitation events. This research advances our understanding of toxicological effects from tyre-related chemicals for drinking-water sources with intensive tyre particle impact, suggesting the need for pretreatment strategies and environmentally benign tyre additives. Although tyre-related chemicals are raising concerns, information about their toxicity after water disinfection is still lacking. Data on Chinese hamster ovary cell cytotoxicity now show that chloramine, chlorine and ozone disinfection substantially elevated the cytotoxicity of tyre-impacted water.