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THE INDUCTION OF ABERRANT CRYPT FOCI IN THE COLONS OF MALE F344/N RATS EXPOSED TO TRIHALOMETHANE MIXTURES IN THE DRINKING WATERS
Citation:
Sistrunk, C. M., S. Kilburn, M H. George, A E. Swank, AND A B. DeAngelo. THE INDUCTION OF ABERRANT CRYPT FOCI IN THE COLONS OF MALE F344/N RATS EXPOSED TO TRIHALOMETHANE MIXTURES IN THE DRINKING WATERS. Presented at American Water Works Association Microbial/Disinfection By-products Effects Symposium, Lisle, IL, March 24-26/2001.
Description:
For over a century the chlorination of drinking water has been the most widely used disinfection process to prevent the spread of waterborne infections. Chlorination of surface waters produces a wide variety of byproducts (DBP) which are found in finished drinking water. The trihalomethanes (THM), comprised of chloroform (TCM), bromodichloromethane (BDCM), chlorodibromomethane (CDBM), and bromoform (TBM), are the predominant DBPs formed by chlorine disinfection (Krasner et at., J. Amer. Water Works Assoc. 81: 41-53, 1989). In waters containing low levels of bromide, TCM is the predominant THM formed. Increasing bromide concentrations shifts the spectrum of the THMs toward the brominated species.
The THMs have been found to produce cancer in rodents (NIH Publication 88-2537; NTP TR 321, 1987; NCI Publication NTIS No. PB264018/AS) when administered by com oil gavage for two years. Two of them, BDCM and TBM increased the incidence of large bowel cancer in male and female rats. (NTP Technical Report No. 350). A more recent study from our laboratory found that BDCM administered in the drinking water to male F344/N rats did not induce colon cancer (George et al, Proc. Amer. Assoc. Cancer Res. 40: 349, 1999). However, it did enhance the formation of hepatocellular adenomas at the lowest dose.