Chen WH, Wang CY, Huang TH. Formation and fates of nitrosamines and their formation potentials from a surface water source to drinking water treatment plants in Southern Taiwan. Chemosphere. 2016 Jul 29;161:546-554. doi: 10.1016/j.chemosphere.2016.07.027.
Nitrosamines are toxic and emerging disinfection byproducts. In this study, three drinking water treatment plants (DWTPs) in southern Taiwan treating the same source water in Gaoping River with comparable technologies were selected. The objective was to evaluate the formation and fates of six nitrosamines and their formation potentials (FPs) from a surface water source to drinking water. Albeit decreased further downstream in the river, four nitrosamine-FPs were observed in the source water due to anthropogenic pollution in the upstream areas. In the DWTPs, nitrosamines were formed and NDMA was the main species. While high organic carbon concentrations indicated elevated nitrosamine-FPs in the source water, NDMA formation in the DWTPs was more positively associated with reductions of water parameters that quantify organic matters with double bonded ring structures. Although precursor removal via pre-oxidation is a viable approach to limit nitrosamine formation during post-disinfection, this study clearly indicates that a great portion of NDMA in treated water has been formed in the 1st oxidation step of drinking water treatment. The pre-oxidation simulations in the lab demonstrated the impact of pre-chlorination on nitrosamine formation. Given the limited removal in conventional treatment processes, avoiding nitrosamine-FPs in sources and/or nitrosamine formation during pre-oxidation become important issues to control the threats of nitrosamines in drinking water. Under current circumstance in which pre-oxidation is widely used to optimize the treatment effectiveness in many DWTPs, its adverse effect by forming nitrosamines needs to be carefully minimized and using technologies other than pre-chlorination (e.g., pre-ozonation) may be considered.
Ji-Hyun Lee, Jeong-Eun Oh. A comprehensive survey on the occurrence and fate of nitrosamines in sewage treatment plants and water environment. Science of the Total Environment 556 (2016) 330–337.
A comprehensive examination of nitrosamines was conducted in a water system, which included sewage treatment plants (STPs), river water, and seawater to understand their characteristic occurrence and fates in whole real water system. The concentrations of nitrosamines were highest in the STP influent (1440–29,100 ng/L), followed by the river water (26.0–5180 ng/L), the STP effluent (9.58–310 ng/L), and seawater (44.2–155 ng/L). The samples were especially affected by proximity to the industrial zone and the samples collected near industrial complex had much higher levels than others with different distribution patterns. In the STPs, nitrosamines were mostly eliminated during biological treatment processes (86.7–95.0%), while they were formed through chlorination processes (−59.6 to −27.7%), which is consistent with previous surveys. The primary clarifier showed insignificant elimination tendencies (5.6–28.2%). Although removal by ultraviolet light was effective (73.2–94.1%), more surveys may be needed because of conflicting results in other studies. Among water quality parameters, nitrosamines in waste water were linked with organic carbon and nitrogen levels.
Er Bei, Yuanyuan Shu, Shixiang Li, Xiaobin Liao, Jun Wang, Xiaojian Zhang, Chao Chen, Stuart Krasner. Occurrence of nitrosamines and their precursors in drinking water systems around mainland China. Water Research 98 (2016)
N-Nitrosamines (NAs) in drinking water have attracted considerable attention in recent years due to their high carcinogenicity, frequent occurrence, and their potential regulation. During the past three years, we have collected about 164 water samples of finished water, tap water, and source water from 23 provinces, 44 cities from large cities to small towns, and 155 sampling points all over China. The occurrence of NAs in the finished and tap water was much higher in China than that in the U.S. Nine NAs were measured and NDMA had the highest concentration. The occurrence of NDMA was in 33% of the finished waters of water treatment plants and in 41% of the tap waters. The average NDMA concentration in finished and tap waters was 11 and 13 ng/L, respectively. Formation potentials (FPs) of source waters were examined with an average NDMA FP of 66 ng/L. Large variations in NA occurrence were observed geographically in China and temporally in different seasons. The Yangtze River Delta area, one sub-area in East China, had the highest concentrations of NAs, where the average NDMA concentrations in the finished and tap water were 27 and 28.5 ng/L, respectively, and the average NDMA FP in the source water was 204 ng/L. NA control may be achieved by applying breakpoint free chlorination and/or advanced treatment of ozone e granular activated carbon process to remove the NA precursors before disinfection.
Wang W, Yu J, An W, Yang M. Occurrence and profiling of multiple nitrosamines in source water and drinking water of China. The Science of the Total Environment. 2016 Feb 17;551-552:489-495. doi: 10.1016/j.scitotenv.2016.01.175.
The occurrence of multiple nitrosamines was investigated in 54 drinking water treatment plants (DWTPs) from 30 cities across major watersheds of China, and the formation potential (FP) and cancer risk of the dominant nitrosamines were studied for profiling purposes. The results showed that N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA) and N-nitrosodi-n-butylamine (NDBA) were the most abundant in DWTPs, and the concentrations in source water and finished water samples were not detected (ND) -53.6ng/L (NDMA), ND -68.5ng/L (NDEA), ND -48.2ng/L (NDBA). The frequencies of detection in source waters were 64.8%, 61.1% and 51.8%, and 57.4%, 53.7%, and 37% for finished waters, respectively. Further study indicated that the FPs of the three main nitrosamines during chloramination were higher than those during chlorination and in drinking water. The results of Principal Components Analysis (PCA) showed that ammonia was the most closely associated factor in nitrosamine formation in the investigated source water; however, there was no significant correlation between nitrosamine-FPs and the values of dominant water-quality parameters. The advanced treatment units (i.e., ozonation and biological activated carbon) used in DWTPs were able to control the nitrosamine-FPs effectively after disinfection. The target pollutants posed median and maximum cancer risks of 2.99×10-5 and 35.5×10-5 to the local populations due to their occurrence in drinking water.
Toxicology studies of mixtures have additional complications and their applicability to risk assessment is a developing science. This work should be considered hypothesis generating. In general, conducting risk assessments for individual chemicals yields very conservative results. Addressing mixtures is very speculative and the combinations are endless.
Ma F, Zhang Z, Jiang J, Hu J. Chromium (VI) potentiates the DNA adducts (O6-methylguanine) formation of N-nitrosodimethylamine in rat: Implication on carcinogenic risk. Chemosphere. 2015 Jul 2;139:256-259. doi: 10.1016/j.chemosphere.2015.06.077.
Chromium (VI) [Cr(VI)] and nitrosamines such as N-nitrosodimethylamine (NDMA) exist commonly in the environment. To evaluate the potential influence of Cr(VI) co-exposure on the carcinogenic risk of NDMA, Female Wistar rats were treated with various concentrations of Cr(VI) and/or NDMA via drinking water for 15days and the DNA adducts (O6-methylguanine, O6-MeG) of NDMA in liver tissue was used as a bioindicator. The results showed that Cr(VI) synergistically enhanced the O6-MeG formation, which could lead to an increase in DNA damage and carcinogenic potential. Although Cr(VI) did not alter the CYP 2E1 enzyme activity, it decreased GSH content, which would be an potential mechanism for the potentiated O6-MeG formation by Cr(VI) co-exposure. These results would contribute to the development of quantitative risk assessment of NDMA or even for a group of nitrosamines under environmental mixture exposure.
Anthony Fristachi and Glenn Rice. Estimation of the total daily oral intake of NDMA attributable to drinking water. Journal of Water and Health, Vol 5, No 3, pp 341–355 2007 doi:10.2166/wh.2007.030
Disinfection with chlorine and chloramine leads to the formation of many disinfection by-products including N-Nitrosodimethylamine (NDMA). Because NDMA is a probable human carcinogen, public health officials are concerned with its occurrence in drinking water. The goal of this study was to estimate NDMA concentrations from exogenous (i.e., drinking water and food) and endogenous (i.e., formed in the human body) sources, calculate average daily doses for ingestion route exposures and estimate the proportional oral intake (POI) of NDMA attributable to the consumption of drinking water relative to other ingestion sources of NDMA. The POI is predicted to be 0.02% relative to exogenous and endogenous NDMA sources combined. When only exogenous sources are considered, the POI was predicted to be 2.7%. The exclusion of endogenously formed NDMA causes the POI to increase dramatically, reflecting its importance as a potentially major source of exposure and uncertainty in the model. Although concentrations of NDMA in foods are small and human exposure to NDMA from foods is quite low, the contribution from food is predicted to be high relative to that of drinking water. The mean concentration of NDMA in drinking water would need to increase from 2.1 × 10-3 mg/L to 0.10 mg/L, a 47-fold increase, for the POI to reach 1%, relative to all sources of NDMA considered in our model, suggesting that drinking water consumption is most likely a minor source of NDMA exposure.
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Water-specific trends were found in this study…..
Shah, A., Krasner, SW, Lee, CF, von Gunten, U. and WA Mitch. Tradeoffs in Disinfection Byproduct Formation Associated with Precursor Pre-oxidation for Control of N-Nitrosodimethylamine Formation. Environ Sci Technol. 2012 Mar 30.
Adstract: Chloramines in drinking water may form N nitrosodimethylamine (NDMA). Various primary disinfectants can deactivate NDMA precursors prior to chloramination. However, they promote the formation of other byproducts. This study compared the reduction in NDMA formation due to chlorine, ozone, chlorine dioxide, and UV over oxidant exposures relevant to Giardia control coupled with post-chloramination under conditions relevant to drinking water practice. Ten waters impacted by treated wastewater, poly(diallyldimethylammonium chloride) (polyDADMAC) polymer or anion exchange resin were examined. Ozone reduced NDMA formation by 50% at exposures as low as 0.4 mg×min/L. A similar reduction in NDMA formation by chlorination required ~60 mg*min/L exposure. However, for some waters chlorination actually increased NDMA formation at lower exposures. Chlorine dioxide typically had limited efficacy regarding NDMA precursor destruction; moreover, it increased NDMA formation in some cases. UV decreased NDMA formation by ~30% at fluences >500 mJ/cm2, levels relevant to advanced oxidation. For the selected pre-treatment oxidant exposures, concentrations of regulated trihalomethanes, haloacetic acids, bromate, and chlorite typically remained below current regulatory levels. Chloropicrin and trichloroacetaldehyde formation were increased by pre-ozonation or medium pressure UV followed by post-chloramination. Among pre-oxidants, ozone achieved the greatest reduction in NDMA formation at the lowest oxidant exposure associated with each disinfectant. Accordingly, pre-ozonation may inhibit NDMA formation with minimal risk of promotion of other byproducts. Bromide >500 ug/L generally increased NDMA formation during chloramination. Higher temperatures increased NDMA precursor destruction by pre-oxidants, but also increased NDMA formation during post-chloramination. The net effect of these opposing trends on NDMA formation was water-specific.
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