Health Hazard Alert: Benzidine, o-Tolidine and o-Dianisidine Based Dyes

This alert cautions of the potential health hazards that could result from excessive exposure to benzidine-, o-tolidine-, and o- dianisidine-based dyes. Recent data from animal tests, case reports, and other sources about the carcinogenic effects and metabolism of these dyes have come to the attention of the Occupational Safety and Health Administration and NIOSH. Both agencies have reviewed the data and conclude that the findings establish the potential of these dyes to cause cancer in humans. The intent of this document is to summarize the information available of the carcinogenic effects and metabolism of these dyes and to provide guidance so that employers, employees, and physicians may work together to reduce potential health hazards that could result from excessive exposure to these dyes.