Nontarget Discovery of an Emerging Class of Chlorobenzenediol DBPs in Chlorinated and Chloraminated Drinking Water with High Developmental Toxicity

Aromatic disinfection byproducts (DBPs) can account for up to 36% of total organic halogen (TOX) in chlorinated drinking water and may be key drivers of developmental toxicity. However, aromatic DBPs reported to date cannot fully explain the observed TOX or developmental toxicity of drinking water. In this study, 17 chlorobenzenediols were identified in chlor(am)inated drinking water using gas chromatography–high resolution mass spectrometry (GC-HRMS). Total concentrations of chlorobenzenediols in tap water from seven cities ranged from 15 to 116 ng/L, with a mean of 54 ng/L. These levels are higher than previously reported for eight classes of aromatic DBPs and halobenzoquinones. Eleven chlorobenzenediols also formed during chlor(am)ination of Suwannee River natural organic matter (NOM), indicating that NOM is an important precursor. Five chlorobenzenediols have a reported LC50 and/or EC50 of less than 1 mg/L for various organisms, indicating that they are classified as very toxic chemicals and are likely to be among the most developmentally toxic aromatic DBPs discovered. Considering that the chlorobenzenediol concentrations in drinking water were higher than eight classes of reported aromatic DBPs and halobenzoquinones, they are likely to have a much more significant impact on drinking water developmental toxicity than other known aromatic DBPs.