A direct resazurin test for measuring chemical toxicity

A rapid, simple, and inexpensive biochemical test for use in the mass screening of chemical compounds for toxicity was developed. The test is based on direct measurement of the inhibition of microbial dehydrogenase activity, as affected by a toxicant, in a well buffered DMSO‐resazurin solution. The addition of 5% DMSO to the reaction mixture allows the toxicity determination of compounds with low water solubility, thus facilitating measurement of the effects of important environmental contaminants on microbiota. The test has been applied to 15 selected chemicals which represent a vast range of environmental contaminants. As well as a routine screening procedure for chemical toxicity, this new resazurin test can be used as a tool in the study of structure‐activity relationship.