Benzidine and Its Metabolites in the Urine of Workers Exposed to Benzidine-Based Azo Dyes

摘要

Samples of urine from workers potentially exposed to Direct Black 38 and other azo dyes were assayed for the free benzidine analogs, mono- and diacetyl metabolites and alkaline hydrolyzable conjugates using a specific electron-capture gas chromatographic procedure developed at the NCTR. A colorimetric screening method based on the reaction of extracted free aromatic amines with 2,4,6-trinitrobenzene sulfonic acid was used by investigators at the National Institute for Occupational Safety and Health (NIOSH) to assay the same samples. Residues of benzidine, monoacetylbenzidine, 2,4-diaminoazobenzene and alkaline hydrolyzable conjugates of benzidine and 2,4-diaminoazobenzene were found at low ppb levels. Traces of two benzidine congeners, 3,3'-dimethylbenzidine and 3,3'-dimethoxybenzidine were also found. No residues of diacetylbenzidine were detected in any of the samples. The presence of the known human bladder carcinogen, benzidine, and its metabolites in the urine of workers exposed to benzidine-based azo dyes is a cause for concern.