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THE INDUCTION OF COLON NEOPLASIA IN MALE RATS EXPOSED TO TRIHALOMETHANES (THMS) IN THE DRINKING WATER
Citation:
Sistrunk, C. M. AND A B. DeAngelo. THE INDUCTION OF COLON NEOPLASIA IN MALE RATS EXPOSED TO TRIHALOMETHANES (THMS) IN THE DRINKING WATER. Presented at National Minority Research Symposium, Cancun, Mexico, 10/17-20/2001.
Description:
THE INDUCTION OF COLON NEOPLASIA IN MALE RATS EXPOSED TO TRIHALO METHANES (THMs) IN THE DRINKING WATER
Christopher Sistrunk and Tony DeAngelo, North Carolina Central University and US Environmental Protection Agency
The THMs are the most widely distributed and the most concentrated of the chlorine disinfection by-products (D BPs). Bromodichloromethane (BDCM) and bromoform (TBM) administered in corn oil were found to increase the incidence of colon neoplasia in the rat. Since THMs occur together in finished drinking water, we initiated a study to evaluate the ability of a mixture high in brominated THMs (Krasner et al., J. Amer. Water Works Assoc., 81: 41-53, 1989) to induce colon neoplasia in male F344 rats. The animals were exposed to mixtures of THMs at lOx, 10 Ox, 1,000x, and 10,000x ambiant concentrations. Water containing 0.25% emulphor (negative control), 30 mg azoxymethane/kg injected ip (positive control) and 477mg TBM/L( equal to 1 O,OOOX mixture) were included. Colon aberrant crypt foci (ACF) or neoplasia were scored at 13, 26 and 52 weeks. At 13 weeks the incidence (% of animals with ACF) was 100% (A OM), 63% (TBM) and 88% (10,000X THM). The 26 week incidence of ACF was 12% (negative control), 100% (A OM and TBM), and 63%,88%, and 88% in the100X, 1000X, and 10,000X THM groups respectively. At 52 weeks the incidence of ACF declined in all groups from earlier time points. Pathologic analysis demonstrated an adenomatous polyp and hyperplasia in one animal in the 477 mg TBM/L and an adenocarcinoma in one animal from the 10,000X treatment group. We consider these biologically significant. This is the first report of D BPs administered in drinking water inducing neoplasia in animals at a site concordant with the findings of epidemiological studies.
(This is an abstract of a proposed presentation and does not necessarily relflect the view of the EP A).