Occurrence and Stability of Chlorophenylacetonitriles: A New Class of Nitrogenous Aromatic DBPs in Chlorinated and Chloraminated Drinking Waters

2-Chlorophenylacetonitrile (2-CPAN) and 3,4-dichlorophenylacetonitrile (3,4-DCPAN), representatives of a new class of nitrogenous aromatic disinfection byproducts, were first identified and quantified in chlorinated and chloraminated drinking waters. The impacts of pH, disinfectant residuals, and quenching agents on the stability of two chlorophenylacetonitriles (CPANs) were investigated. The two CPANs slightly degraded with increasing pH (5–9) and chlorination doses (0–4 mg/L) after 5 days, and NH₂Cl did not cause degradation of CPANs. Among the commonly used quenching agents, the reaction between sodium sulfite and CPANs was negligible, whereas the others reduced CPANs by varying extents after 7 days. Notably, the two CPANs in finished water collected from seven drinking water treatment plants were quantified. 2-CPAN was detected between 170 and 530 ng/L with a median concentration of 220 ng/L, whereas 3,4-DCPAN ranged from below method detection limit (100 ng/L) up to 320 ng/L with a median concentration of 130 ng/L. Moreover, cytotoxicity of the CPANs and their aliphatic counterparts was determined using Chinese hamster ovary cells. The LC₅₀ values are 133, 83, 436, 260, 905, 4150, and 8900μM for 2-CPAN, 3,4-DCPAN, chloroacetonitrile, dichloroacetonitrile, chloroacetic acid, dichloroacetic acids, and trichloromethane, respectively. Because of the relatively high stability and high toxic potencies of CPANs, the occurrence of CPANs in drinking water deserves attention.