Recent progress in identification of water disinfection byproducts and opportunities for future research.

Numerous disinfection by-products (DBPs) are formed from reactions between disinfectants and organic/inorganic matter during water disinfection. More than seven hundred DBPs that have been identified in disinfected water, only a fraction of which are regulated by drinking water guidelines, including trihalomethanes, haloacetic acids, bromate, and chlorite. Toxicity assessments have demonstrated that the identified DBPs cannot fully explain the overall toxicity of disinfected water; therefore, the identification of unknown DBPs is an important prerequisite to obtain insights for understanding the adverse effects of drinking water disinfection. Herein, we review the progress in identification of unknown DBPs in the recent five years with classifications of halogenated or nonhalogenated, aliphatic or aromatic, followed by specific halogen groups. The concentration and toxicity data of newly identified DBPs are also included. According to the current advances and existing shortcomings, we envisioned future perspectives in this field.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Level of confidence in DBP identification based on the level system proposed by Schymanski et al. (2014) (Schymanski et al., 2014): Level 1: structure confirmed with a reference standard; Level 2: exact structure was proposed by different evidence; Level 3: candidate structural isomer exist but exact structure was not confirmed; Level 4: specific molecular formula was determined; Level 5: only exact mass (m/z) was measured while formula was not elucidated.
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