Mutagenicity of organic extracts from canadian drinking water in the salmonella/mammalian‐microsome assay

Organic extracts of chlorinated Ontario drinking water samples have been found to induce mutation and lethality in the Salmonella/mammalian-microsome histadine reversion assay. Collections of water were made at water treatment plants in five municipalities in June 1978. To determine the reproducibility of the positive mutagenic effects found, a second sampling at the same plants was performed in September 1978. Preparation of extracts involved passing 200 liter samples through XAD-2 resin columns which were eluted with a mixture of hexane and acetone, and the eluent was evaporated to dryness. For those extracts with sufficient organic matter, dose-related increases in mutagenicity were observed. Extracts of untreated water from a river and a well were weakly mutagenic.