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Although the health benefits of swimming are well-documented, health effects such as asthma and bladder cancer are linked to disinfection by-products (DBPs) in pool water. DBPs are formed from the reaction of disinfectants such as chlorine (Cl) or bromine (Br) with organics in the water. Our previous study (Daiber et al., Environ. Sci. Technol. 50, 6652; 2016) found correlations between the concentrations of classes of DBPs and the mutagenic potencies of waters from chlorinated or brominated swimming pools and spas. We extended this study by identifying significantly different concentrations of 21 individual DBPs in brominated or chlorinated pool and spa waters as well as identifying which DBPs and additional DBP classes were most associated with the mutagenicity of these waters. Using data from our previous study, we found that among 21 DBPs analyzed in 21 pool and spa waters, the concentration of bromoacetic acid was significantly higher in Br-waters versus Cl-waters, whereas the concentration of trichloroacetic acid was significantly higher in Cl-waters. Five Br-DBPs (tribromomethane, dibromochloroacetic acid, dibromoacetonitrile, bromoacetic acid, and tribromoacetic acid) had significantly higher concentrations in Br-spa versus Cl-spa waters. Cl-pools had significantly higher concentrations of Cl-DBPs (trichloroacetaldehyde, trichloromethane, dichloroacetic acid, and chloroacetic acid), whereas Br-pools had significantly higher concentrations of Br-DBPs (tribromomethane, dibromoacetic acid, dibromoacetonitrile, and tribromoacetic acid). The concentrations of the sum of all 4 trihalomethanes, all 11 Br-DBPs, and all 5 nitrogen-containing DBPs were each significantly higher in brominated than in chlorinated pools and spas. The 8 Br-DBPs were the only DBPs whose individual concentrations were significantly correlated with the mutagenic potencies of the pool and spa waters. These results, along with those from our earlier study, highlight the importance of Br-DBPs in the mutagenicity of these recreational waters.

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.