The Salmonella mutagenicity assay in a surface water quality monitoring program based on a 20-year survey.

Since 1979, the Environmental Agency of São Paulo State in Brazil, CETESB, has been using the Salmonella mutagenicity assay to assess the quality of natural waters. This paper is a compilation of data obtained during the last 20 years from more than a thousand samples. Potencies up to 30,000 revertants/l were observed in 137 positive samples. The Salmonella typhimurium strain TA98 was more sensitive than TA100; 79% of the mutagenicity was detected by this strain, regardless of the presence of S9-mix. A classification of the mutagenic response was proposed to facilitate in the dissemination of the information to the public. The classification was low, moderate, high and extreme for samples with mutagenic potency (revertants/l equivalent) of < 500, 500-2500, 2500-5000 and > 5000, respectively. As a result of this effort to standardize methodologies, compile and classify the mutagenic effect of water pollution, in 1998, the Salmonella mutagenicity assay was officially and systematically included in the São Paulo State Water Quality Monitoring Program. This assay has proven to be a useful tool in the identification of important pollution sources. Correction and prevention actions in Water Pollution Control Programs were generated as a result.