Disinfection byproducts (DBPs) are compounds that form between disinfectants and other constituents during water treatment and are associated with long-term health effects. Trihalomethanes (THMs) are a group of DBPs that are regulated by the US EPA and have ubiquitous presence in our drinking waters. However, nitrogenous DBPs (N-DBPs), such as haloacetonitriles (HANs), are orders of magnitude more toxic than THMs. Aniline, a benzene ring with an amino group, is a nitrogenous moiety that is present in a number of industrial and agricultural chemicals but has not been evaluated as a DBP precursor. In this work, we observed that aniline and substituted anilines, act as potent precursors to both THMs and HANs under chlorination and bromination conditions. At halogen to nitrogen molar ratio (X:N) of 5, chloroform formed at concentrations 2–3 times higher than dichloroacetonitrile (DCAN) from 30 min–24 h under chlorination conditions; After integrating these concentrations with the toxicity, DCAN contributed 55-85 times more to the cytotoxicity of the chlorinated sample than the chloroform. Moreover, bromoform and dibromoacetonitrile (DBAN) formed at comparable levels during bromination over a similar time profile and X:N ratio. Our results indicate that aniline forms HANs and THMs at comparable levels to tryptophan and phenol, which are respective high-yield precursors. Furthermore, 2-ethyl substitution of aniline substantially decreased the formation of DCAN by 50% during chlorination, whereas it enhanced the formation of DBAN almost 2-fold during bromination. Our work is ongoing to investigate key intermediates after aniline ring cleavage using liquid chromatography–high resolution mass spectrometry. Our overall findings suggest that (1) aniline is an overlooked precursor to HANs and THMs and (2) the differences between chlorination and bromination challenge the conventional thinking that chlorinated and brominated disinfection byproducts form analogously from the same precursor.

Halogenation of anilines: Formation of regulated and unregulated disinfection byproducts

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