Excretion of thioethers in urine after exposure to electrophilic chemicals

Electrophilic agents--a class of chemicals that includes most genotoxic compounds--can be inactivated by reaction with glutathione or other SH-bearing molecules. The conjugates so formed often appear in the urine as mercapturic acids or other thioether products. This paper critically reviews the suitability of the urinary thioether assay as a method for the detection of exposure to electrophilic agents or their precursors. In practice, the greatest value of the thioether assay appears to lie in its signal function. This is demonstrated for cigarette smokers and industrial workers involved in chemical waste incineration. Whenever increased thioether excretion is observed, it is likely to be due to exposure to one or more suspect compounds. However, when the thioether concentration ranges within the limits of the normal value, one must not conclude that there is no, or negligible, exposure. More specific applications of the assay of thio compounds in urine allow development of selective methods that may be useful for biological monitoring.