Granular activated carbon (GAC) adsorption is well-established for controlling regulated disinfection byproducts (DBPs), but its effectiveness for unregulated DBPs and DBP-associated toxicity is unclear. In this study, GAC treatment was evaluated at three full-scale chlorination drinking water treatment plants over different GAC service lives for controlling 61 unregulated DBPs, 9 regulated DBPs, and speciated total organic halogen (total organic chlorine, bromine, and iodine). The plants represented a range of impacts, including algal, agricultural, and industrial wastewater. This study represents the most extensive full-scale study of its kind and seeks to address the question of whether GAC can make drinking water safer from a DBP perspective. Overall, GAC was effective for removing DBP precursors and reducing DBP formation and total organic halogen, even after >22 000 bed volumes of treated water. GAC also effectively removed preformed DBPs at plants using prechlorination, including highly toxic iodoacetic acids and haloacetonitriles. However, 7 DBPs (mostly brominated and nitrogenous) increased in formation after GAC treatment. In one plant, an increase in tribromonitromethane had significant impacts on calculated cytotoxicity, which only had 7–17% reduction following GAC. While these DBPs are highly toxic, the total calculated cytotoxicity and genotoxicity for the GAC treated waters for the other two plants was reduced 32–83% (across young–middle–old GAC). Overall, calculated toxicity was reduced post-GAC, with preoxidation allowing further reductions.

Pools and spas are enjoyed throughout the world for exercise and relaxation. However, there are no previous studies on mutagenicity of disinfected spa (hot tub) waters or comprehensive identification of disinfection byproducts (DBPs) formed in spas. Using 28 water samples from seven sites, we report the first integrated mutagenicity and comprehensive analytical chemistry of spas treated with chlorine, bromine, or ozone, along with pools treated with these same disinfectants. Gas chromatography (GC) with high-resolution mass spectrometry, membrane-introduction mass spectrometry, and GC-electron capture detection were used to comprehensively identify and quantify DBPs and other contaminants. Mutagenicity was assessed by the Salmonella mutagenicity assay. More than 100 DBPs were identified, including a new class of DBPs, bromoimidazoles. Organic extracts of brominated pool/spa waters were 1.8× more mutagenic than chlorinated ones; spa waters were 1.7× more mutagenic than pools. Pool and spa samples were 2.4 and 4.1× more mutagenic, respectively, than corresponding tap waters. The concentration of the sum of 21 DBPs measured quantitatively increased from finished to tap to pool to spa; and mutagenic potency increased from finished/tap to pools to spas. Mutagenic potencies of samples from a chlorinated site correlated best with brominated haloacetic acid concentrations (Br-HAAs) (r = 0.98) and nitrogen-containing DBPs (N-DBPs) (r = 0.97) and the least with Br-trihalomethanes (r = 0.29) and Br-N-DBPs (r = 0.04). The mutagenic potencies of samples from a brominated site correlated best (r = 0.82) with the concentrations of the nine HAAs, Br-HAAs, and Br-DBPs. Human use increased significantly the DBP concentrations and mutagenic potencies for most pools and spas. These data provide evidence that human precursors can increase mutagenic potencies of pools and spas and that this increase is associated with increased DBP concentrations.

This study reveals key disinfection byproduct (DBP) toxicity drivers in drinking water across the United States. DBPs, which are ubiquitous in drinking water, form by the reaction of disinfectants, organic matter, bromide, and iodide and are generally present at 100–1000× higher concentrations than other contaminants. DBPs are linked to bladder cancer, miscarriage, and birth defects in human epidemiologic studies, but it is not known as to which DBPs are responsible. We report the most comprehensive investigation of drinking water toxicity to date, with measurements of extracted whole-water mammalian cell chronic cytotoxicity, over 70 regulated and priority unregulated DBPs, and total organic chlorine, bromine, and iodine, revealing a more complete picture of toxicity drivers. A variety of impacted waters were investigated, including those impacted by wastewater, agriculture, and seawater. The results revealed that unregulated haloacetonitriles, particularly dihaloacetonitriles, are important toxicity drivers. In seawater-impacted water treated with chloramine, toxicity was driven by iodinated DBPs, particularly iodoacetic acids. In chlorinated waters, the combined total organic chlorine and bromine was highly and significantly correlated with toxicity (r = 0.94, P < 0.01); in chloraminated waters, total organic iodine was highly and significantly correlated with toxicity (r = 0.80, P < 0.001). These results indicate that haloacetonitriles and iodoacetic acids should be prioritized in future research for potential regulation consideration.

Disinfection byproducts (DBPs) are a ubiquitous source of chemical exposure in drinking water and have been associated with serious health impacts in human epidemiologic studies. While toxicology studies have pinpointed DBPs with the greatest toxic potency, analytical methods have been lacking for quantifying complete classes of most toxic DBPs at sufficiently low quantification limits (ng/L). This new method reports the parts-per-trillion quantification for 61 toxicologically significant DBPs from 7 different chemical classes, including unregulated iodinated haloacetic acids (HAAs) and trihalomethanes (THMs), haloacetaldehydes, haloketones, haloacetonitriles, halonitromethanes, and haloacetamides, in addition to regulated HAAs and THMs. The final optimized method uses salt-assisted liquid–liquid extraction in a single extraction method for a wide range of DBPs, producing the lowest method detection limits to-date for many compounds, including highly toxic iodinated, brominated, and nitrogen-containing DBPs. Extracts were divided for the analysis of the HAAs (including iodinated HAAs) by diazomethane derivatization and analysis using a GC-triple quadrupole mass spectrometer with multiple reaction monitoring, resulting in higher signal-to-noise ratios, greater selectivity, and improved detection of these compounds. The remaining DBPs were analyzed using a GC-single quadrupole mass spectrometer with selected ion monitoring, utilizing a multimode inlet allowed for lower injection temperatures to allow the analysis of thermally labile DBPs. Finally, the use of a specialty-phase GC column (Restek Rtx-200) significantly improved peak shapes, which improved separations and lowered detection limits. Method detection limits for most DBPs were between 15 and 100 ng/L, and relative standard deviations in tap water samples were mostly between 0.2 and 30%. DBP concentrations in real samples ranged from 40 to 17 760 ng/L for this study.

Hydraulic fracturing wastewaters discharged to surface water have led to elevated bromide and iodide levels, as well as enhanced formation of brominated trihalomethanes, haloacetic acids, haloacetonitriles, and iodo-trihalomethanes at downstream drinking water treatment plants, in chlorinated effluent from wastewater treatment plants, and in controlled laboratory studies. This enhanced formation of brominated and iodinated disinfection byproducts (DBPs) raises concerns regarding human health, because they are much more toxic than chlorinated DBPs. This study represents the first nontarget, comprehensive analysis of iodinated DBPs formed in chloraminated produced waters associated with hydraulic fracturing of shale and conventional gas formations. Fifty-six iodo-phenolics were identified, comprising three homologous series of mono-, di-, and tri-iodinated phenols, along with two new classes of DBPs: iodomethylphenols and iododimethylphenols. Four iodo-phenolics (2-iodophenol, 4-iodophenol, 2,4,6-triiodophenol, and 4-iodo-2-methylphenol) were investigated for mammalian cell cytotoxicity. All were cytotoxic, especially 2,4,6-triiodophenol, which was more cytotoxic than all trihalomethanes and most haloacetic acids. In addition, geogenic organic compounds present in the oil and gas produced waters, including methylphenol and dimethylphenol, were found to be potential precursors to these iodo-DBPs.