||Environmental Health Research and Testing, Inc., Cincinnati, OH. ;Pathology Associates, Inc., West Chester, OH.;Health Effects Research Lab., Cincinnati, OH.
The effect of chloroform (CHC13), administered at 0, 900, and 1800 mg/l in the drinking water, on the carcinogenic potency of 1,2-dimethylhydrazine (DMH) was investigated. Groups of forty male Fisher 344 rats were given one of the three drinking water solutions for 39 weeks following the subcutaneous injection of 200 mg/kg DMH, a known gastrointestinal (GI) tract carcinogen in this animal strain. When tumors from the GI tract were pooled there was a highly significant (p <0.001) decrease in total number of tumors per group with increasing concentration of drinking water CHC13. In the control group (0 mg/l CHC13), 14/39 (36%) of the animals developed tumors of the GI tract, including the duodenum, jejunum, stomach, cecum and colon. In contrast, the incidence of tumors in the two groups of rats given CHC13 in the drinking water was significantly lower (p <0.001; 900 mg/l CHC13, 12.8%; and 1800 mg/l CHC13, 12.5%). A similar relationship was obtained when colon tumors were analyzed independently (p = 0.01). These results demonstrate that CHC13 in the drinking water inhibits carcinogenesis in the rat GI tract. (Copyright (c) 1989 by the Society of Toxicology.)