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Chemical evaluation of drinking water disinfection byproducts

Final Report Summary - CHE-WADISBYPRO (Chemical evaluation of drinking water disinfection byproducts)

Water disinfection is required to reduce morbidity and mortality from waterborne diseases. However, the generation of disinfection by-products (DBPs) during water disinfection treatments may also pose health risks. To date, more than 50% of the organic halogenated compounds formed during water disinfection still remain unidentified. Iodinated DBPs have been reported to be among the most genotoxic of all DBPs regulated and/or identified to date. This type of DBP has been also reported to be present in waters with low iodide content. Therefore, other potential sources of iodine need to be explored. In this context, the main goals of ChE-WADISBYPRO are 1) to produce and chemically characterize water concentrates of chloramine-and chlorine-derived DBP mixtures to use them in toxicity studies, and 2) to investigate the formation of iodo-DBPs from iodinated X-ray contrast media (ICMs).
The specific objectives of ChE-WADISBYPRO can be summarized as follows:
1. production of representative and stable drinking water DBP concentrates from chloramination and chlorination scenarios;
2. chemical characterization of the DBP concentrates: identification of newly formed DBPs;
3. quantification of DBPs in chloraminated and chlorinated drinking water;
4. comparison of DBP mixtures generated under chloramination and chlorination scenarios and risk assessment; and
5. comprehensive identification and quantification of iodo-DBPs generated by ICM, including formation mechanisms.
The outgoing phase of ChE-WADISBYPRO took place at the U.S. Environmental Protection Agency, whereas the return phase was carried out at the Spanish Council for Scientific Research. The work performed during the implementation of ChE-WADISBYPRO includes:
- the development and validation of two analytical methodologies to quantify ten haloacetaldehydes in waters;
- the performance of high-volume (120 L and 17 L) chlorination and chloramination reactions of waters
- the generation of DBP concentrates from:
o chlorinated and chloraminated surface water ( containing four different ICMs, i.e. iopamidol, iohexol, sodium diatrizoate and iopromide,
o chlorinated swimming pool water
o chlorinated tap water
o chlorinated and chloraminated surface water from a highly polluted river (Llobregat River, Barcelona, Spain)
o chlorinated and chloraminated Milli-Q water containing Suwanee River natural organic matter (NOM) (International Humic Substances Society –IHSS–); and different bromide and iodide concentrations.
o chlorinated and chloraminated Milli-Q water containing North Lake NOM (IHSS), and different bromide and iodide concentrations.
- Quantitative analysis of selected DBPs, i.e. haloacetaldehydes, iodo trihalomethanes, and iodo acetic acids, by means of gas chromatography-mass spectrometry in the chlorinated and chloraminated waters.
- Non-target analysis of the generated DBP concentrates to identify new iodo-DBPs.
Main results achieved in the framework of ChE-WADISBYPRO are:
- The confirmation of the ICM iopamidol as a iodine source in water that contributes to iodo-DBP formation. This was not observed for the other investigated ICM, i.e. iopromide, iohexol and diatrizoate.
- The identification for the first time of new iodo-DBPs in disinfected waters:
o Iodoacetaldehyde (IAL) in chloraminated drinking waters and iodoacetonitrile in chlorinated waters. Their presence was confirmed with analytical standards.
o Trichloro-iodoacetonitrile, trichloro-iodomethane and iodo-butyl ethyl ester in chlorinated waters were tentatively identified in chlorinated waters. Their identity could not be confirmed with analytical standards, since they are not commercially available to date.
- In the light of the results obtained in the DBP concentrates generated under chlorination and chloramination scenarios:
o Iodo trihalomethane (I-THM) formation was favored during chlorination treatment, whereas iodo haloacetic acid (I-HAA) and IAL formation was enhanced during chloramination scenarios.
o Iodo-DBP formation was favored in waters containing iopamidol that were chlorinated, and in waters containing high concentrations of bromide and iodide treated with either chlorine or chloramines.
o Iopamidol was also observed to affect formation mechanism of regulated DBPs and other commonly measured DBPs, which were formed at higher concentrations during chlorination than during chloramination treatments.
o The most abundant I-THMs detected were dichloroiodomethane (DCIM), chlorobromoiodomethane (CBIM) and chlorodioodomethane (CDIM).
o The commonly detected I-HAAs were iodoacetic acid (IAA) and chloroiodoacetic acid (ClAA).
o Llobregat river waters showed similar bromide and iodide incorporation factors to the tested iodide and bromide fortified NOM solutions regarding I-THMs formation, despite the fact that bromide and iodide concentrations were very different (17 ppb of iodide and 800 ppb of bromide in Llobregat River vs. 400 ppb of bromide and 40- 100 ppb of iodide in NOM solutions). In all cases species with one atom of iodine were favored. Overall total concentration
The potential toxicity of the DBP concentrates generated during chlorination and chloramination of waters containing different ICMs is currently being investigated with a battery of different toxicity bioassays carried out by U.S. EPA researchers. The toxicity tests carried out will investigate developmental effects in zebrafish embryo, genotoxicity and cytotoxicity in mammalian cells (Chinese hamster ovary cells), mutagenicity in Salmonella, and toxicity to bladder cells.
All DBP concentrates generated in ChE-WADISBYPRO are being further investigated to potentially identify unknown non-iodinated DBPs. Their analysis by means of high resolution MS will be further explored to aid in this task.