Formation and Decomposition of New Iodinated Halobenzoquinones during Chloramination in Drinking Water

Abstract

Previously four chlorinated and brominated halobenzoquinones were reported as new disinfection byproducts (DBPs) in drinking water, which have drawn great concern due to their high toxicity. In this study, three new iodinated halobenzoquinones, including 2-chloro-6-iodo-1,4-benzoquinone (2,6-CIBQ), 2-bromo-6-iodo-1,4-benzoquinone (2,6-BIBQ), and 2,6diiodo-1,4-benzoquinone (2,6-DIBQ), were detected and identified in drinking water for the first time. Their cytotoxicity was evaluated, and their formation under various conditions was examined. Since they were not stable during chloramination, their further decomposition during chloramination was also explored. The results indicated that the concentrations of 2,6-CIBQ, 2,6-BIBQ, and 2,6-DIBQ in drinking water were in the ranges of 0.7−1.3, 1.8−8.0, and 0.4−15.9 ng/L, respectively. Compared with 2,6dibromo-1,4-benzoquinone, the iodinated halobenzoquinones were generally more cytotoxic. The formation of 2,6-DIBQ during chloramination was significantly affected by the iodide concentration, pH, and natural organic matter. The five tested iodinated halobenzoquinones decomposed during chloramination following pseudo-first-order decay, with the decomposition rate constants in the rank order of 2,6-CIBQ > 2,6-BIBQ > 2,6-DIBQ > 2,3-diiodo-1,4-benzoquinone >2-iodo-1,4-benzoquinone. Nine polar halogenated intermediates as well as ten aliphatic halogenated DBPs were detected as the decomposition products of 2,6-DIBQ during chloramination, based on which the decomposition pathways of 2,6-DIBQ during chloramination were proposed and verified.

Haloquinone Chloroimides as Toxic Disinfection Byproducts Identified in Drinking Water

“…The isomer of higher polarity would easily enter into the cell and induce higher cytotoxicity. Similar results were also reported for the cytotoxicity of halobenzoquinones in CHO-K1 cells and HepG2 cells. , Third, the lowest cytotoxic concentration (induced a statistically significant reduction as compared to the negative control) of five HQCs and 2,6-DCBQ was calculated by the Holm-Sidak method with the power (1-β) ≥ 0.8 at α = 0.05 after a significant F value was obtained ( P < 0.05). The lowest cytotoxic concentration of six analytes was 2,6-DCQC (20 μM), 2,6-DCBQ (160 μM), 2-CQC (15 μM), 3-CQC (80 μM), 2,6-DCMQC (120 μM), and 2,6-DBQC (60 μM).…”

“…Similar results were also reported for the cytotoxicity of halobenzoquinones in CHO-K1 cells and HepG2 cells. 35,50 Third, the lowest cytotoxic concentration (induced a statistically significant reduction as compared to the negative control) of five HQCs and 2,6-DCBQ was calculated by the Holm-Sidak method with the power (1-β) ≥ 0. S6 and S7.…”

“…The HepG2 cell line, a human hepatocyte carcinoma cell line commonly used in DBP metabolism and toxicity studies, − was acquired from the cell bank of the Chinese Academy of Sciences (Shanghai, China) for evaluating the cytotoxicity of HQCs. The HepG2 cells were cultured in Dulbecco’s modified Eagle medium (DMEM) supplemented with 10% fetal bovine serum (GIBCO; #16000-044) and 1% 1000 U penicillin/streptomycin solution (HyClone).…”

Occurrence and Distribution of Disinfection Byproducts in Domestic Wastewater Effluent, Tap Water, and Surface Water during the SARS-CoV-2 Pandemic in China

“…The three Cl-aromatic DBPs, including 3,5-DCl-2-HBA (19.7 ng/L), 3,5-DCl-4-HB (17.7 ng/L), and 2,4,6-TClP (15.1 ng/L), were the dominant species among the nine aromatic halogenated DBPs and accounted for 70%, which was much higher than those of the measured Br-aromatic (27%) and I-aromatic DBPs (3%). Increasing the chlorine dose for emergency disinfection can accelerate the formation and decomposition of aromatic (non)­halogenated DBPs and thus increase the formation of aliphatic DBPs, including THMs, HAAs, and other DBPs, in disinfected waters. − This might account for the low detection frequencies and concentrations of the nine aromatic DBPs measured in Wuhan and Beijing. For all tap water samples, NDMA (22.9 ng/L), NMEA (13.8 ng/L), and NDEA (8.9 ng/L) were the three most dominant species and accounted for 69% among nine NAs.…”

Ozonation Treatment Increases Chlorophenylacetonitrile Formation in Downstream Chlorination or Chloramination

“…Disinfection byproducts (DBPs) are inevitably generated during drinking water disinfection by the reaction of disinfectant with organics and halides . Numerous epidemiologic and metabolomic observations have identified associations between the long-term consumption of chlorinated drinking water and adverse health risks such as abnormal pregnancy outcomes, bladder cancer, and cardiac birth defects. − Many researchers have aimed to identify the DBP that may act as toxicity drivers in drinking water. − Since chloroform was first reported in chlorinated drinking water in the 1970s, more than 800 DBPs have been identified and confirmed. − Trihalomethanes (THMs) and haloacetic acids (HAAs), carbonaceous DBPs (C-DBPs), are currently regulated by the United States Environmental Potency Agency, but no evidence has shown that they are drivers of elevated bladder cancer risk. , Nitrogenous DBPs (N-DBPs) are reported to be more toxic than C-DBPs. , Recently, a number of aromatic DBPs have been identified in drinking waters. − Aromatic DBPs are of concern due to their high toxicity, often 3 to 4 orders of magnitude higher than regulated DBPs. , Furthermore, it has been reported that the metabolic rate of aromatic nitrogenous groups in heterotrophic organisms was significantly lower than that of non-nitrogenous aromatic groups, indicating they are slowly metabolized by humans. , In other words, aromatic N-DBPs in drinking water may be important components of the overall toxicity. Recently, chlorophenylacetonitriles (CPANs), an emerging class of aromatic N-DBPs, have been identified in drinking water. , Chronic cytotoxicity tests based on Chinese hamster ovarian (CHO) cells have shown that the CPANs are 2 to 3 orders of magnitude more cytotoxic than regulated THMs and HAAs.…”