Biomarkers of xenobiotic exposures.

Direct measurement of xenobiotic (foreign) chemicals is not always feasible as an exposure assessment,--owing to rapid metabolism, sequestration into fatty tissues, or lack of suitable assay methods. Furthermore, suspect exposures often involve complex mixtures of organics. In these circumstances, indirect biomarkers of exposure can be most helpful. This paper reviews four urinary parameters that hold promise as biomarkers of exposure in occupational and environmental settings: glucaric acid (end-product of the glucuronidation pathway), thioethers (end-product of glutathione reaction with electrophilic or alkylating agents), porphyrin pattern (altered with disruption in heme biosynthesis), and the Ames mutagenicity test.