In recent years, the environmental impact of tyre-derived chemicals has garnered increasing scientific scrutiny, particularly their infiltration into aquatic ecosystems. These contaminants, primarily originating from the wear and tear of automobile tyres, find their way into surface waters via runoff, raising significant concerns due to their widespread presence and potent ecotoxicological properties. Despite extensive research highlighting their prevalence and harm to aquatic life, a crucial gap remains in understanding the repercussions of these compounds after routine potable water treatments. A compelling new study by Liu, Wang, Hu, and colleagues published in Nature Water delivers groundbreaking insights into how common water disinfection processes drastically alter the toxicity profiles of waters burdened with tyre-derived contaminants.
The research employed a sophisticated toxicological assay using Chinese hamster ovary (CHO) cells to quantify cytotoxic effects—essentially measuring the degree of cell damage or death when exposed to treated water samples. The findings were stark: disinfection methods routinely employed at water treatment facilities, including chloramination, chlorination, and ozonation, considerably exacerbated the cytotoxicity of tyre-impacted waters. Specifically, chloramine treatment resulted in a fivefold increase in cytotoxicity, chlorine caused a fourfold increase, and ozone produced a 1.4-fold elevation compared to the untreated samples. Notably, these figures were many times higher—ranging from three to sixfold—than the cytotoxicity observed in disinfected waters sourced from pristine lake environments, underscoring the unique and compelling risk posed by tyre-associated contaminants during disinfection.
Delving deeper into the chemical transformations underpinning this heightened cytotoxicity, the study deployed non-target analytical techniques, a cutting-edge approach that enables comprehensive identification of chemical species without prior specification. The results revealed a pronounced presence of halogenated organic byproducts in disinfected tyre-impacted waters, with brominated and iodinated compounds emerging as principal contributors. These findings are particularly significant given that halogenation, a common reaction during disinfection, often increases the stability and toxicity of organic pollutants. The interaction between tyre additives and disinfectants leads to the emergence of these complex halogenated products, which likely amplify the cellular toxicity observed.
The researchers highlighted a subset of 33 chemical entities—comprising benzothiazoles, phenols, benzophenones, and various arylamines—that cumulatively accounted for just under 5% of total organic carbon mass in the samples but disproportionately contributed between 25 and 36% of the observed cytotoxicity. This disproportionate toxicity contribution signals that even trace concentrations of certain transformation products can drastically impact water safety and suggests that conventional water quality metrics focusing solely on carbon mass or bulk chemical measures might underestimate actual health risks.
An important epidemiological implication derived from this work is the potential for marked increases in drinking water toxicity following extreme precipitation events, which are expected to become more frequent and intense due to climate change. These hydrological episodes likely amplify tyre particulate runoff into water bodies, raising the raw influent load of hazardous chemicals entering treatment plants. Consequently, the formation of toxic halogenated byproducts during disinfection could spike episodically, posing unpredictable threats to public health and challenging current water safety protocols.
This pioneering study also underscores the urgent need for reconsidering standard water treatment practices and precursor chemical controls. While disinfection remains indispensable for eliminating microbial pathogens, the unintended side reactions with ubiquitous environmental contaminants illustrate a critical blind spot. Future water treatment strategies may require integrating advanced pretreatment methods aimed at removing or transforming tyre-derived compounds before conventional disinfection steps. Such approaches could minimize the formation of toxic transformation products downstream and improve drinking water safety.
Complementing process innovations, the study advocates for a paradigm shift in the tire manufacturing industry towards designing environmentally benign additives. Current formulations contain chemicals prone to transformation into harmful halogenated derivatives upon environmental release and water treatment. Developing additive chemistries that degrade into innocuous substances or resist halogenation could drastically reduce the downstream cytotoxic burden and align tyre production with sustainability goals.
On a technical front, the research showcases the value of combining toxicological bioassays with comprehensive non-target chemical analyses. This dual approach enables not only a precise quantification of biological impact but also mechanistic insights into the molecular culprits behind toxicity. Such methodologies represent a new frontier in environmental toxicology, moving beyond traditional targeted detection to unravel complex mixtures and transformation dynamics in real-world scenarios.
The implications of this study extend beyond water treatment facilities and regulatory agencies. Public health experts, environmental policymakers, and urban planners will need to consider tyre-degradation products as emerging contaminants of concern, especially as urbanization and vehicular traffic density rise globally. Moreover, monitoring programs should evolve to detect these transformation products routinely and assess their risks in conjunction with traditional pollutants.
In parallel, the research raises thought-provoking questions about cumulative human exposure to multiple compounds with overlapping toxicities. While this study focused on mammalian cell cytotoxicity, the broader toxicological landscape—incorporating genotoxicity, endocrine disruption, and long-term chronic effects—remains largely uncharted. These dimensions warrant urgent investigation to fully elucidate the health consequences of consuming disinfected tyre-impacted water over extended periods.
From an ecological perspective, while this study centered on drinking water safety, the findings suggest potential risks to aquatic organisms inhabiting untreated or partially treated waters as well. Halogenated transformation products formed naturally or during water treatment could accumulate in aquatic food webs, causing physiological stress or mortality, thereby undermining ecosystem integrity. Long-term monitoring and ecotoxicological assessments should thus be prioritized.
In summary, this study by Liu et al. decisively positions tyre-derived chemical contaminants as hidden yet significant hazards in the context of drinking water treatment. The revelation that disinfection processes can inadvertently amplify toxicity invites urgent reassessment of both water treatment protocols and urban source control measures. As climate patterns evolve and urban runoff challenges water quality, holistic and forward-looking solutions will be vital to safeguard human and environmental health in the coming decades.
The unfolding story of tyre contaminant toxicity exemplifies the intricate interplay between anthropogenic chemical inputs and water treatment chemistry. It underscores the complexity of managing emerging contaminants and highlights the essential role of multidisciplinary scientific inquiry. Researchers, engineers, and policymakers must collaborate to devise innovative and sustainable strategies that not only eliminate pathogens but also curtail the unintended generation and dissemination of chemically modified toxins.
Ultimately, this research not only advances fundamental understanding but also serves as an urgent call to action. Water quality management, once centered predominantly on microbial safety, must now integrate chemical toxicity frameworks that address dynamic environmental transformations. Embracing this challenge will ensure cleaner, safer water supplies and healthier ecosystems, thereby upholding public trust and environmental stewardship well into the future.
Subject of Research:
Toxicological impact of tyre-derived chemicals in drinking water following disinfection processes.
Article Title:
Unveiling the mammalian cell cytotoxicity of tyre-impacted water in disinfection.
Article References:
Liu, H., Wang, R., Hu, C. et al. Unveiling the mammalian cell cytotoxicity of tyre-impacted water in disinfection. Nat Water (2025). https://doi.org/10.1038/s44221-025-00469-w
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