Studies on the potent bacterial mutagen, 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone: aqueous stability, XAD recovery and analytical determination in drinking water and in chlorinated humic acid solutions.

3-Chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) was detected by gas chromatography/mass spectrometry in drinking water samples from 3 locations in the U.S.A., and also in a chlorinated humic acid solution. MX appears to account for a significant proportion of the mutagenicity of these samples, as measured in the Ames test using strain TA100 without metabolic activation. Studies on recovery of MX from spiked water samples by XAD-2/8 resin adsorption/acetone elution indicated that sample acidification prior to resin adsorption was essential to the effective recovery of MX. The stability of MX in aqueous solution was pH and temperature dependent. At 23 degrees C the order of stability, based on persistence of mutagenic activity was found to be: pH 2 greater than pH 4 greater than pH 8 greater than pH 6. The half-life at pH 8 and 23 degrees C was 4.6 days. One of the degradation products has been tentatively identified as 2-chloro-3-(dichloromethyl)-4-oxo-2-butenoic acid, an open form of MX which appears to be in the "E" configuration. Overall, these results suggest that MX is formed during water chlorination as a result of reaction of chlorine with humic substances, and that a substantial fraction of the MX formed is likely to persist throughout the distribution system.

Mutagenic by-products from chlorination of humic acid.

Chlorination of humic and fulvic acid results in the formation of direct-acting mutagenicity, detectable in the Salmonella/microsome assay (Ames test). This mutagenicity is being characterized as part of an overall effort aimed at evaluating potential health risks associated with the presence of mutagenic chemicals in drinking water. A number of chlorinated organic compounds, including several known mutagens, have been identified and quantified in diethyl ether extracts of chlorinated humic acid solutions. However, the total mutagenicity of these compounds accounts for only about 7% of the original mutagenicity. Synergistic or antagonistic interactions among the identified components have been ruled out as possible explanations for the failure to account for a higher percentage of the activity. Recent progress has been made to separate the activity into neutral and strong acid fractions. Further isolation of the strong acids by high-pressure liquid chromatography (HPLC) has resulted in the purification of the mutagenicity into a major peak of activity with a specific mutagenicity of about 20,000 TA100 revertants per milligram. Several trichlorohydroxyfuranone isomers have been tentatively identified in this fraction. The contribution of these types of compounds to the mutagenicity of chlorinated humic acid is under investigation.

Results of toxicological testing of Jefferson Parish pilot plant samples.

Five toxicological tests were performed using concentrated drinking water samples collected at a pilot-scale drinking water treatment plant that had streams treated with different disinfectants (no disinfectant, ozone, chlorine dioxide, monochloramine, or chlorine) before treatment with granular activated carbon (GAC). The toxicological tests used in this study were the Ames Salmonella assay, a subchronic in vivo toxicity assay in mice, the SENCAR mouse skin initiation-promotion assay, a rat liver foci assay, and the lung adenoma assay in strain A mice. These tests were conducted to determine the general toxicity and the mutagenic/carcinogenic potential associated with the use of disinfection and/or GAC in the treatment of drinking water. The stability of the mutagenic activity of the samples tested was determined by repeated analysis using the Ames Salmonella assay. Results indicated that the samples remained mutagenic for the duration of the tests. All the drinking water concentrates (4000 X) prepared by the XAD resin adsorption procedure failed to provide statistically significant indication of carcinogenic activity in the SENCAR mouse, rat liver foci, and the lung adenoma assays. However, concentrates of the chlorine, chlorine dioxide, and monochloramine treated waters gave consistent mutagenic responses in the Ames Salmonella assay. GAC was effective for 6 months in removing both the mutagenicity of chlorine-treated water and the potential of water to become mutagenic when treated with chlorine. In the in vivo, subchronic 30-day toxicity test in mice, some statistically significant differences in organ weights and body weights of animals exposed to different concentrates of some of the samples were observed. However, a consistent pattern of these differences indicating overt toxicity was not detected.

Water disinfection: microbes versus molecules--an introduction of issues.

"Water is, apart from the air one breathes, the only nutrient which is, as a matter of necessity, consumed by every human being from the first day to the last day of his existence, and it is consumed in considerably larger quantities than any other nutritional substance."(1)

Comparative metabolism of 1,2,4-trichlorobenzene in the rat and rhesus monkey.

1,2,4-Trichloro[14C]benzene (TCB) was administered po (10 mg/kg) and iv (10 mg/kg) to rats and rhesus monkeys. Urine was collected at 24 hr and the major urinary metabolites were quantified and identified. By 24 hr, the monkey had excreted 22% of the iv dose and roughly 40% of the po dose in the urine. Less than 1% of the radioactivity was found in the monkey's feces. An isomeric pair of 3,4,6-trichloro-3,5-cyclohexadiene-1,2-diol glucuronides accounted for between 48 and 61% of the urinary metabolites. Glucuronides of 2,4,5- and 2,3,5-trichlorophenol (TCP) accounted for 14 to 37%, and unconjugated TCP's accounted for 1-37% of the monkey's urinary metabolites. For the rat, 84% of the po dose and 78% of the iv dose were collected in the urine by 24 hr; 11% and 7%, respectively, were the amounts collected in the feces. Two isomers, 2,4,5- and 2,3,5-, of N-acetyl-S-(trichlorophenyl)-L-cysteine accounted for 60-62% of the rat's urinary metabolites. Free 2,4,5- and 2,3,5-isomers of trichlorothiophenol amounted to 33% of the urinary metabolites in the po dosed rats and 28% in the iv dosed rats; free 2,4,5- and 2,3,5-TCP's amounted to 1% and 10%, respectively. These results show that there is a sharp division in the types of conjugates formed in the metabolism of 1,2,4-TCB by the rat and rhesus monkey.