IngentaConnect FAILURE OF MONOCHLOROACETIC ACID AND TRICHLOROACETIC ACID ADMINIS...

Authors: Deangelo A. B.; Bernard F.; Bernard D.; Most M.; Olson G. R.

Source: Journal of Toxicology and Environmental Health, Volume 52, Number 5, 20 November 1997 , pp. 425-445(21)

Abstract:

The chlorinated acetic acids monochloroacetic acid MCA and trichloroacetic acid TCA are found as chlorine disinfection by-products in finished drinking-water supplies. TCA has been demonstrated to be a mouse liver carcinogen. A chronic study in which male Fischer 344 N rats were exposed for 104 wk to TCA and MCA in the drinking water is described. Animals, 28 d old, were exposed to 0.05, 0.5, or 2 g L MCA, or 0.05, 0.5, or 5 g L TCA. The 2.0 g L MCA was lowered in stages to 1 g L when the animals began to exhibit signs of toxicity. A time-weighted mean daily MCA concentration MDC of 1.1 g L was calculated over the 104-wk exposure period. Time-weighted mean daily doses MDD based upon measured water consumption were 3.5, 26.1, and 59.9 mg kg d for 0.05, 0.5, and 1.1 g L MCA, respectively; TCA MDD were 3.6, 32.5, and 363.8 mg kg d. Nonneoplastic hepatic changes were for the most part spontaneous and age related. No evidence of hepatic neoplasia was found at any of the MCA or TCA doses. The incidence of neoplastic lesions at other sites was not enhanced over that in the control group. Drinking water concentrations of 0.5 g L MCA produced a moderate to severe toxicity as reflected by a depressed water consumption and growth rate. A no-observed-effects level NOEL for carcinogenicity of 0.5 g L 26.1 mg kg d MCA was calculated. TCA at drinking water levels as high as 5 g L produced only minimal toxicity and growth inhibition and provided a NOEL of 364 mg kg d. Our results demonstrate that under the conditions of this bioassay, MCA and TCA were not tumorigenic in the male F344 N rat.

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FAILURE OF MONOCHLOROACETIC ACID AND TRICHLOROACETIC ACID ADMINISTERED IN THE DRINKING WATER TO PRODUCE LIVER CANCER IN MALE F344 N RATS