Hi all…in an effort to avoid chlorinated disinfection byproduct (DBP) formation in distribution systems many drinking water utilities switched from free chlorine to chloramination. While there was a learning curve associated with this disinfectant it did meet objectives to reduce regulated chlorinated DBP formation (i.e. THMs and HAAs). It has been recognized that some DBP exposure can occur through inhalation of steam in showers and boiling water for example (as opposed to simply drinking tap water) but I don’t think anyone had considered DBP formation during cooking with iodized table salt until around the time the study referred to below was published. In addition to chlorinated DBPs, there has been much effort dedicated to identify brominated, nitrogenated, and iodinated DBPs in the past decade. A large number have been identified and toxicity studies are on-going but it is recognized that some of these are more “toxic” than chlorinated DBPs.
A 2016 study investigating the formation of iodinated disinfection byproducts (I-DBPs) revealed that numerous new I-DBPs were detected when cooking with iodized table salt using chloraminated tap water. The authors investigated toxicity and concentration data of nine major I-DBPs. Their study concludes with “many of the I-DBPs identified in the simulated cooking water samples were phenolic I-DBPs, which generally exhibited substantially higher development toxicity than aliphatic I-DBPs. Considering I-DBPs’ potential adverse implications for human health and based on their formation under various disinfection and cooking conditions we thus proposed several practical suggestions for controlling their formation during cooking e.g., performing cooking with chlorinated tap water containing relatively low levels of chlorine residual instead of chloraminated tap water (commercially available purified water which is free of disinfectant residual is also preferred), with KIO3-fortified table salt instead of KI-fortified table salt, with a relatively long interval between the sequential additions of wheat flour and iodized table salt, at a relatively low cooking temperature, and with a relatively short cooking time.
It looks like there is still much work to do in terms of compound identification, toxicity testing, and risk analysis.
Bill
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Identification, toxicity and control of iodinated disinfection byproducts in cooking with simulated chlor(am)inated tap water and iodized table salt
Yang Pan, Xiangru Zhang, Yu Li
Water Research, Volume 88, 1 January 2016, Pages 60-68
https://www.sciencedirect.com/science/article/pii/S0043135415302682
Abstract
“Chlorine/chloramine residuals are maintained in drinking water distribution systems to prevent microbial contamination and microorganism regrowth. During household cooking processes (e.g., soup making), the residual chlorine/chloramines in tap water may react with the iodide in iodized table salt to form hypoiodous acid, which could react with remaining natural organic matter in tap water and organic matter in food to generate iodinated disinfection byproducts (I-DBPs). However, I-DBPs formed during cooking with chloraminated/chlorinated tap water are almost completely new to researchers. In this work, by adopting precursor ion scan of m/z 127 using ultra performance liquid chromatography/electrospray ionization-triple quadrupole mass spectrometry, many new polar I-DBPs formed during cooking with chloraminated/chlorinated tap water were detected and proposed with structures, of which 3-iodo-4-hydroxybenzaldehyde, 3-iodo-4-hydroxybenzoic acid, 3-iodo-4-hydroxy-5-methylbenzoic acid, diiodoacetic acid, 3,5-diiodo-4-hydroxybenzaldehyde, 3,5-diiodo-4-hydroxybenzoic acid, 2,6-diiodo-4-nitrophenol, 2,4-diiodo-6-nitrophenol, and 2,4,6-triiodophenol were confirmed with standard compounds. With the aid of ultra fast liquid chromatography/ion trap-time of flight-mass spectrometry, molecular formula identification of five new I-DBPs (C8H5O4I, C7H4NO4I, C8H5O5I, C7H4NO5I, and C8H6O3I2) was achieved. A developmental toxicity with a recently developed sensitive bioassay was conducted for the newly identified I-DBPs, suggesting that phenolic I-DBPs (except for iodinated carboxyphenols) were about 50–200 times more developmentally toxic than aliphatic I-DBPs. The major I-DBPs in a baseline simulated cooking water sample were determined to be from 0.72 to 7.63 μg/L. Polar I-DBPs formed under various disinfection and cooking conditions were compared, and suggestions for controlling their formation were provided.”
