How Much of the Total Organic Halogen and Developmental Toxicity of Chlorinated Drinking Water Might Be Attributed to Aromatic Halogenated DBPs?

Abstract

Although >700 disinfection byproducts (DBPs) have been identified, >50% of the total organic halogen (TOX) in drinking water chlorination is unknown, and the DBPs responsible for the chlorination-associated health risks remain largely unclear. Recent studies have revealed numerous aromatic halo-DBPs, which generally present substantially higher developmental toxicity than aliphatic halo-DBPs. This raises a fascinating and important question: how much of the TOX and developmental toxicity of chlorinated drinking water can be attributed to aromatic halo-DBPs? In this study, an effective approach with ultraperformance liquid chromatography was developed to separate the DBP mixture (from chlorination of bromide-rich raw water) into aliphatic and aromatic fractions, which were then characterized for their TOX and developmental toxicity. For chlorine contact times of 0.25−72 h, aromatic fractions accounted for 49−67% of the TOX in the obtained aliphatic and aromatic fractions, which were equivalent to 26−36% of the TOX in the original chlorinated water samples. Aromatic halo-DBP fractions were more developmentally toxic than the corresponding aliphatic fractions, and the overall developmental toxicity of chlorinated water samples was dominated by aromatic halo-DBP fractions. This might be explained by the considerably higher potentials of aromatic halo-DBPs to bioconcentrate and then generate reactive oxygen species in the organism.

Molecular-Level Insights into the Formation of Traditional and Novel Halogenated Disinfection Byproducts

“…Organic DBPs form when naturally present dissolved organic matter (DOM) reacts with disinfectants such as free available chlorine (i.e., HOCl/OCl – , Cl 2 , and Cl 2 O), , which is effective, inexpensive, and provides residual disinfectant during distribution. , Organic DBPs regulated in the United States (i.e., four trihalomethanes, THMs, and five haloacetic acids, HAAs) − represent only a fraction of DBPs that are present in treated water. Known unregulated DBPs, including haloacetonitriles (HANs) or aromatic DBPs, contribute significantly to the toxicity of chlorinated drinking water. − Furthermore, the vast majority of organic DBPs produced during chlorination have not yet been identified and their toxicity is unknown. ,,, …”

“…8−12 Furthermore, the vast majority of organic DBPs produced during chlorination have not yet been identified and their toxicity is unknown. 9,10,12,13 DBP formation during disinfection is influenced by both the concentration and composition of DOM, which ranges widely in drinking water sources. Most utilities in the United States rely on surface waters and, as a result, the composition and reactivity of DOM in these sources are well characterized.…”

Research Progress of the Endocrine-Disrupting Effects of Disinfection Byproducts

“…[ 30 , 31 , 32 ]. However, recent studies revealed that commonly regulated DBPs cannot be the major contributor to the adverse health effects induced by consuming chlorinated drinking water [ 33 , 34 ]. Compared with regulated DBPs, some emerging DBPs, such as halobenzoquinones, iodinated DBPs, nitrogenous DBPs, and aromatic DBPs, are more worthy of attention [ 35 , 36 ].…”

Fate of New Persistent Organic Chemical 3,6-Dichlorocarbazole in Chlorinated Drinking Water

“…The assessment of human health threats of PHCZs in drinking water requires a thorough understanding of their transformations and fates, especially during potentially prolonged interaction with chlorination disinfectants, such as booster chlorination in delivery systems, which may generate highly toxic secondary chlorinated byproducts. 23 There is growing concern about the artificial chemicals acting as precursors of the DBPs and the possibility of these nextgeneration DBPs exhibiting long-term or even enhanced bioactivity. 24−26 For example, perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS) can be generated from zwitterionic and cationic precursor compounds during chlorination disinfection, and novel chlorination byproducts of tryptophan are formed during water disinfection.…”

“…This study mainly focuses on the transformation of PHCZs in drinking water. The assessment of human health threats of PHCZs in drinking water requires a thorough understanding of their transformations and fates, especially during potentially prolonged interaction with chlorination disinfectants, such as booster chlorination in delivery systems, which may generate highly toxic secondary chlorinated byproducts . There is growing concern about the artificial chemicals acting as precursors of the DBPs and the possibility of these next-generation DBPs exhibiting long-term or even enhanced bioactivity. − For example, perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS) can be generated from zwitterionic and cationic precursor compounds during chlorination disinfection, and novel chlorination byproducts of tryptophan are formed during water disinfection. , It has been reported that the chlorination process may also lead to the transformation of some organic pollutants to small molecule disinfection byproducts. − The transformation processes of PHCZs induced by photolysis have been reported, where dehalogenation, hydroxylation, and hydrolysis are suggested as the major photodegradation mechanisms of PHCZs in liquid solution. − However, the transformation of PHCZs during the chlorination process in drinking water has not been investigated, and the generation of possible chlorination byproducts has also not been studied.…”