Chromium (VI) potentiates mutagenesis by sodium azide but not ethyl methanesulfonate.

A fluctuation test using Salmonella typhimurium strain 1535 has been used in an experimental protocol to assess biological effects of interactions between chromium (VI), such as K2CrO4, and two DNA-damaging agents, ethyl methanesulfonate (EMS), and sodium azide. Mutagenicity, expressed as the average number of mutations induced over a parallel control, was determined for the compounds alone and in combination. The significance of the differences between the "expected" response, calculated by simple addition of the responses from the individual tests, and the observed response when the combination was tested, were estimated by chi square. For the combination of K2CrO4 and NaN3, the response was significantly greater than expected suggesting a possible potentiation of mutagenesis. The opposite (a less-than-additive response) was found for the K2CrO4/EMS combination. Both effects were found to be dose related to the concentration of potassium chromate used. Toxicity of the compounds or their combinations to the bacteria could not explain the results.