Comparative Cytotoxicity of Drinking Water Disinfection By-Product Mixtures Produced During Chlorination and Chloramination

Chlorinated and chloraminated waters containing characterized natural organic matter (NOM) were compared on the basis of cytotoxicity, disinfection by-product (DBP), and total organic halogen (TOX) levels. Cytotoxicity was evaluated using a growth inhibition assay (GIA) in NCM460 human colon cells. Without adding iodide or nitrate or using medium pressure ultraviolet (UV) pretreatment, the chlorinated water was more cytotoxic than the chloraminated water. At elevated iodide levels and using pretreatment with medium pressure UV, the chloraminated water was the most cytotoxic of all disinfected samples evaluated. This is likely due to the formation of iodinated DBPs, possibly enhanced by degradation of the NOM with UV but present at levels below detection of the analytical methods used. This current research shows that the GIA is able to detect these differential cytotoxic responses, and can provide more insight into changes in water quality than DBP and TOX measurements alone.Master of Scienc