Chlorinated drinking water is mutagenic and causes 3-methylcholanthrene type induction of hepatic monooxygenase

Acid/neutral fractions of 4 chlorinated drinking water samples were tested for mutagenicity in the Ames' test and injected intraperitoneally to 10- and 20-day-old Wistar rats at doses of 200 and 100 liters of water/kg body weight. Cytochrome P-450 mediated enzyme activities of ethylmorphine-N-demethylase (EMND), 7-ethoxycoumarin-O-deethylase (ECOD), 7-ethoxyresorufin-O-deethylase (EROD) and 7-pentoxyresorufin-O-dealkylase (PEROD) were determined in the 9000 g supernatant fraction of liver homogenate. EROD was introduced by the concentrates. The induction was related to the mutagenic activity. About 4-fold increase in activity was observed with the most mutagenic sample. PEROD was also slightly enhanced. EMND and ECOD activities were not affected by the lower dose, but the higher dose caused inhibition of 30-40%. Although the extracts were not toxic to bacteria, they were unexpectedly toxic to rats. It is concluded that the samples contained 3-methylcholanthrene (3-MC) type inducer(s).