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Chapter 3
Effect of Boiling on Halogenated DBPs and Their Developmental Toxicity in Real Tap Waters Jiaqi Liu, Xiangru Zhang,* and Yu Li Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China *E-mail:
[email protected].
The use of chlorine for disinfection results in the formation of halogenated disinfection by-products (DBPs) in tap water. Evidence has shown that halogenated DBPs may cause chronic adverse effects on human health, and brominated DBPs are generally significantly more toxic than their chlorinated analogues. Previously, the authors’ group found that boiling of a simulated tap water for 5 min significantly reduced the overall levels of brominated and chlorinated DBPs, thus reducing the cytotoxicity of the simulated tap water to mammalian cells. In this study, we further investigated the effect of boiling on the level and developmental toxicity of halogenated DBPs in two “real” tap water samples. With a novel precursor ion scan approach using electrospray ionization-triple quadrupole mass spectrometry, the whole pictures of polar brominated and chlorinated DBPs in both tap water samples without and with boiling were revealed. After 5 min boiling, the concentrations of total organic bromine (a collective parameter for all brominated DBPs) in the two tap water samples decreased by 43.6% and 37.5%, respectively; the concentrations of total organic chlorine (a collective parameter for all chlorinated DBPs) in the two tap water samples decreased by 39.0% and 57.1%, respectively; the developmental toxicity of the two tap water samples decreased by 53.0% and 57.1%, respectively. This study suggests a simple
© 2015 American Chemical Society In Recent Advances in Disinfection By-Products; Xie, et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2015.
way to reduce the adverse health effect of halogenated DBPs in humans through tap water ingestion.
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Introduction With the purpose of inactivating harmful microorganisms and eradicating waterborne diseases, disinfection has been applied in drinking water treatment. Chlorine is a widely used disinfectant for drinking water. Chlorine-disinfected drinking water is distributed to households via a public water distribution system, in which a certain level of chlorine residual should be maintained to prevent regrowth of microorganisms in the water, especially when breaks or cracks occur in the pipeline. However, chlorinated disinfection by-products (DBPs) unintentionally form (from the reaction between hypochlorous acid and natural organic matter in source water) during chlorination in a drinking water treatment plant and in a water distribution system. Besides, source waters contain bromide ions resulting from geologic dissolution, seawater intrusion and human activities (1). During chlorination, hypochlorous acid can oxidize bromide to hypobromous acid, which subsequently reacts with natural organic matter in source water to generate brominated DBPs. Brominated DBPs have been reported to exhibit significantly higher toxicity than their chlorinated analogues (2–6). Humans are unavoidably exposed to DBPs via water ingestion. It has been reported that the total cancer risks from the commonly known haloacetic acids and trihalomethanes mainly result from tap water ingestion (7). In most Western nations, tap water is directly drunk, whereas in some Asian nations, people are used to boiling tap water before drinking. Boiling has its own advantages, including effectively removing chlorine or chloramine residual and thus eliminating chlorinous taste and odor of the water (8); inactivating chlorine-resistant pathogenic protozoa Cryptosporidium and Giardia (9); and reducing some major DBPs (including trihalomethanes, haloacetic acids, haloketones, haloacetonitriles, haloaldehydes, and halonitromethanes) (10–12). Recently, a powerful precursor ion scan (PIS) approach with electrospray ionization-triple quadrupole mass spectrometry coupled with ultra performance liquid chromatography (UPLC/ESI-tqMS) has been developed for selectively detecting polar halogenated DBPs (13–19). By using this approach, the authors’ group has studied the effect of boiling on the halogenated DBPs in a simulated tap water, and found that boiling for 5 min significantly reduced the halogenated DBPs and cytotoxicity of the water (20). However, a real tap water may be different from the simulated tap water because a real tap water originates from a real source water, which may contain a variety of organic and inorganic components including (micro)pollutants. Accordingly, the purpose of this study was to determine the effect of boiling on the halogenated DBPs and toxicity in real tap waters. Hutchinson’s group developed an in vivo assay using the sensitive embryo-larval stages of a polychaete, Platynereis dumerilii, which is a cosmopolitan species, extending from the tropics to cold temperate latitudes in both hemispheres (21, 22). The authors’ group modified Hutchinson et al.’s 46 In Recent Advances in Disinfection By-Products; Xie, et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2015.
method and significantly lowered the relative standard deviation to
