Hydrolytic Stabilities of Halogenated Disinfection Byproducts: Review and Rate Constant Quantitative Structure-Property Relationship Analysis

As toxicity studies of disinfection byproducts (DBPs) progress, enhanced knowledge of the stability of DBPs can help determine the likelihood of DBP occurrence in water and thus enable accurate exposure assessments. To elucidate the roles of functional group, halogen number, and halogen type on the hydrolytic stability of halogenated DBPs, this study reviewed the hydrolysis rate constants (k(H)) of six groups of DBPs, including haloacetic acids, trihalomethanes, haloacetaldehydes, haloketones, haloacetonitriles, and cyanogen halides. Quantitative structure-property relationship models were developed and validated via previously tested compounds, and by extrapolation, these models were projected to nontested chemicals of emerging health concern, especially iodinated DBPs. In general, the k(H) values follow the order haloketone > haloacetonitrile > haloacetaldehyde > haloacetic acid > trihalomethane for chlorinated and brominated species, increase with increasing number of halogen atoms within one DBP group, and increase as a function of increasing atomic weight of included halogens (i.e., F<Cl<Br<I). This is the first summary of both regulated and emerging DBPs that uses the novel approach of quantitative structure-property relationship to fit diverse sources of information. Predicted results may orient future studies of the fate and transport of persistent DBP species.