Bottled or tap? Comparison of 64 DBPs, total organic halogen, and calculated toxicity

Bottled water consumption has increased globally at a tremendous rate, however, little is known about levels of disinfection by-products (DBPs) in bottled water beyond the regulated trihalomethanes (THMs), haloacetic acids (HAAs), and bromate. This is important because many bottled waters are sourced from tap water. Using gas chromatography-mass spectrometry, we quantified 64 regulated and priority, unregulated DBPs in 10 popular brands of bottled water, including 50 toxicologically important, unregulated DBPs not measured in previous studies. Several priority, unregulated DBPs were found in bottled water for the first time, including dibromoacetonitrile, chloroacetonitrile, dichloroacetamide, trichloronitromethane, dichloroacetaldehyde, 1,1-dibromopropanone, and 1,1,1-trichloropropanone. Dibromoacetonitrile was present in two Grocery Brand bottled waters, up to 0.2 μg/L, and is particularly important because it is highly cytotoxic, genotoxic, and carcinogenic. Total organic halogen (TOX) was also measured in bottled waters for the first time. All bottled waters contained measurable TOX, with highest TOCl levels in Grocery/Name Brands (up to 31.4 μg/L) and highest TOBr levels in a Name Brand water (up to 7.0 μg/L). A surprising finding was the presence of HAAs and chloroform in one of the Designer Brands, which is supposed to be treated with UV disinfection only. THMs and HAAs were found at the highest levels (0.01-12.4 µg/L), with other priority, unregulated DBPs present at ng/L levels when detected. However, while all bottled waters (even untreated spring waters) contained DBPs, they were present at levels significantly lower than typically found in tap water. For example, total DBP levels ranged from 0.01-22.4 µg/L (mean of 2.6 µg/L) in bottled water, compared to 47.3 µg/L and 52.2 µg/L for chloraminated tap water and other tap waters treated with chlorine and other disinfectants, respectively. Also, fewer DBPs were detected in the bottled waters (3 on average vs. 37 in the tap water). The rank order of lowest to highest mean DBP levels followed: Designer Brands < Grocery Brands < Name Brands (0.6, 3.1, and 3.7 µg/L, respectively). Grocery Brands and Name Brands had higher numbers of DBPs compared to Designer Brands. Brands sourced from spring water generally showed lower overall DBP levels than those labeled as purified. DBP levels varied dramatically with lot number (from the same brand), with large variability in both the number of DBPs detected and concentrations. Finally, two grocery brands, which were purified tap waters, had significantly higher calculated cytotoxicity than other bottled waters sampled, with 43x and 83x the average levels of other bottled waters, but bottled waters overall had quite low calculated cytotoxicity compared to tap water.