Occurrence and toxicity of haloketones: emerging class of disinfection byproducts in drinking water of Nanning City, Southwest China

Haloketones (HKs) are an emerging class of unregulated drinking water disinfection byproducts (DBPs) that are primarily responsible for drinking water cytotoxicity and also exhibit genotoxicity and carcinogenicity. We determined the concentrations of 11 HKs in drinking water and conducted quantitative and comparative analyses of their toxicity. Nine HKs were detected in drinking water from Nanning City in Southwest China, with median concentrations ranging from 0.03 to 3.32 μg/L. 1,1,3-Tribromopropanone and 1-bromo-1,1-dichloropropanone were identified in drinking water for the first time in China. The descending rank order of HK cytotoxicity was 1,3-dichloropropanone > bromopropanone > 1,1,3-tribromopropanone > 1,1,3-trichloropropanone ≈ chloropropanone > 1,1-dichloropropanone > 1,1,3,3-tetrachloropropanone > 1-bromo-1,1-dichloropropanone ≈ 1,1,3,3-tetrabromopropanone > 1,1,1-trichloropropanone ≈ 1,1-dibromopropanone (F_10,208 = 4672.689, P < 0.001). The rank order for HK genotoxicity was 1,3-dichloropropanone > bromopropanone > chloropropanone > 1,1-dibromopropanone > 1,1,3-trichloropropanone ≈ 1,1,3-tribromopropanone > 1-bromo-1,1-dichloropropanone ≈ 1,1,3,3-tetrachloropropanone > 1,1,3,3-tetrabromopropanone > 1,1-dichloropropanone ≈ 1,1,1-trichloropropanone (F_10,66 = 7028.528, P < 0.001). The rank order for HK thiol reactivity was 1,1-dibromopropanone ≈ 1,3-dichloropropanone ≈ chloropropanone ≈ bromopropanone ≈ 1-bromo-1,1-dichloropropanone ≈ 1,1,3-tribromopropanone > 1,1,3,3-tetrabromopropanone > 1,1,3-trichloropropanone ≈ 1,1,3,3-tetrachloropropanone ≈ 1,1-dichloropropanone ≈ 1,1,1-trichloropropanone (F_10,154 = 473.640, P < 0.001). Quantitative structure activity relationship models indicated that HK toxicity was closely correlated with hydrophobicity, boiling point, and topological properties. HKs exhibited higher cytotoxicity and genotoxicity than regulated haloacetic acids and trihalomethanes. In particular, 1,3-dichloropropanone showed higher toxicity than nitrogenous DBPs. Further studies are required to expand the investigation of HK pollution, elucidate their formation and toxic mechanisms, and evaluate the potential human health risks.