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.