During drinking water disinfection, potentially harmful disinfection by-products are formed due to the reaction of organic matter with chlorine. Therefore, in this research, human intestinal epithelial cells (Caco-2) were exposed to haloacetamides (HAcAm) and haloacetic acids (HAAs). A 24, 48 and 72h exposure was conducted to determine the cytotoxicity of these compounds. The unregulated HAcAms were clearly more cytotoxic than the regulated HAAs. Moreover, changing the halogen from Cl to I increased the toxicity extensively. Hence, a membrane fractionation process is developed to split organic matter into three fractions which should facilitate the identification of both HAA and HAcAm precursors after chlorination.