An Examination of Domestic Tap Water Treatments and Their Impact on Average Daily Ingestion Exposure to Halogenated Disinfection Byproducts in Drinking Water
Creators: name: Eslinger, Sara Anne
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2004

description: The impact of in-home tap water treatment on the ingestion of halogenated disinfection byproducts (DBPs) has been examined. This work was performed as part of an epidemiological study examining the potential link between adverse reproductive outcomes and the occurrence of halogenated DBPs in drinking water. Tap water is often pretreated with point-of-use (POU) filtration devices, heated via microwave or kettle, or frozen in preparation of ice before it is consumed. An analysis of these treatments and bottled waters was performed to determine the potential effect they have on the overall ingestion of certain DBPs, specifically four trihalomethanes (THM4), nine haloacetic acids (HAA9), and total organic halide (TOX). The epidemiological study has recruited a cohort of pregnant women from three cities in the United States, two of which are serviced by chloraminated (chlorinated one month each year) tap water that contains either highly chlorinated (Site 1) or highly brominated (Site 3) DBPs. At least 25% of these women drink the majority of their water after POU-filtration. Therefore, four POU devices were examined at homes within Site 1, and two POU devices were further examined in a controlled laboratory experiment in order to simulate a DBP species distribution containing all species and more akin to that in Site 3 water. All four POU devices studied in homes removed greater than 80% of the THM4 concentration over the studied period of POU cartridge capacity, while the pitcher and faucet-mounted POUs, studied in the laboratory, removed an average of 41% and 100% respectively of THM4 on average over 100% capacity. HAA9 and TOX removal varied between 30 and 100% for the studies. Approximately 10% of the cohorts' daily water consumption came from hot beverages prepared with tap water. DBP behavior in waters heated in a kettle to boiling (~93°C) and those heated for 3 minutes in a microwave (~72°C) vary widely depending upon the type and amount of disinfectant residual and the time before consumption. Chloroform is often formed when tap water containing residual free chlorine is heated, while THMs in waters with a chloramine residual will significantly decrease. Heating may cause a slight increase in CI(2)AA concentration and a decrease in bromine-containing HAAs but the total HAA concentrations do not change significantly when heating chlorinated or chloraminated tap water. THM4 concentration in ice tends to decrease while HAA9 increases. None of the THM4 or HAA9 species were detected in any of the bottled water samples examined. Infrequent water collection and estimates of a women's exposure to DBPs based on occasional distribution system data or address alone, not personalized consumption behavior, have been cited as potential sources of exposure misclassification in previous epidemiological studies. This work demonstrates that incorporating POU-filtration and thermal treatment into ingestion exposure may reduce estimates of daily exposure to THM4 and HAA9 by more than 75%. Adjustment factors are calculated that can be used to account for the effect of these treatments on DBP levels and be incorporated into more accurate assignment of exposure in epidemiological studies.