Analytical and Toxicological Characterization of Novel Nitrogen Containing Disinfection Byproducts

  • Author / Creator
    Boyd, Jessica M.
  • Disinfection byproducts (DBPs) are an unwanted consequence of water disinfection. Consumption of chlorinated drinking water has been associated with an increased risk of bladder cancer; however, the DBP or DBPs responsible has not been identified. The N-nitrosamines are a class of DBPs that are known rodent carcinogens. They are more potent than the currently regulated DBPs and may be capable of causing health effects at low ng/L concentrations. Due to these possible health concerns, the study of nitrosamines in drinking water is warranted. Gas chromatography mass spectrometry (GC-MS) is the main technique used for nitrosamine analysis, but cannot directly detect thermally unstable or non-volatile nitrosamines. A liquid chromatography tandem MS (LC-MS/MS) method was developed that is capable of detecting GC-detectable nitrosamines, such as N-nitrosodimethylamine (NDMA), and GC-non-detectable nitrosamines. Using this method, N-nitrosodiphenylamine (NDPhA), a thermally unstable nitrosamine, was detected as a DBP from an authentic drinking water sample. A survey of 38 North American drinking water systems using the LC-MS/MS method found that NDMA was the most commonly detected nitrosamine (28 of 38 systems) followed by NDPhA (6 of 38 systems). A real-time cell electronic sensing (RT-CES) technique was developed and demonstrated as a useful tool for DBP toxicity testing. NDPhA was more cytotoxic than NDMA in four cell lines. Further mechanistic analysis determined that NDPhA induces cell cycle arrest, which is different than other nitrosamines such as NDMA. Studies on nitrosamine formation showed the important role of source water. Disinfectant type alone was not sufficient to determine which nitrosamines are formed. Additional studies determined that diphenylamine (DPhA) can form NDPhA, particularly in the presence of monochloramine. This reaction also formed phenazine and N-chlorophenazine. Further investigation determined that phenazine containing natural products produced by bacteria are also precursors for the phenazine containing DBPs. These results suggest that the currently monitored nitrosamines are not widespread enough to be solely responsible for the observed increase in bladder cancer risk. However, there are several locations where elevated nitrosamine concentrations are a concern. Until the DBP cancer culprit is identified, reduction of overall DBP formation through source water management and careful monitoring of the disinfection process is the best practice to manage cancer risks posed by DBPs.

  • Subjects / Keywords
  • Graduation date
    Fall 2012
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.