Where It Comes From
Manufactured for azo dyes/pigments and analytical reagents; can be present in wastes at dye, plastics, or lab facilities [1][3][4].
How You Are Exposed
Breathing dust or contacting skin during manufacturing, lab use, equipment cleaning, or waste handling; less often via air/water near facilities [2][3][4].
Why It Matters
Classified as reasonably anticipated to be a human carcinogen (NTP) and possibly carcinogenic to humans (IARC Group 2B); also irritates skin/eyes [1][2][3].
Who Is at Risk
Workers in dye/pigment production, labs using o‑tolidine reagents, maintenance/waste handlers, and people without proper ventilation/PPE; neighbors of poorly controlled sites [2][3][4].
How to Lower Your Exposure
Use safer substitutes (e.g., EPA‑recommended DPD methods for chlorine testing), closed systems/local exhaust, protective gloves/eyewear, hygiene, and proper hazardous‑waste disposal [3][5].
References
- [1]IARC Monographs, Volume 77: Some Aromatic Amines, Organic Dyes and Related Exposures (o‑Tolidine). WHO/IARC, 2000.
- [2]NTP, Report on Carcinogens: o‑Tolidine (3,3'-Dimethylbenzidine). U.S. DHHS/NIEHS.
- [3]CDC/NIOSH Pocket Guide to Chemical Hazards: o‑Tolidine dihydrochloride. Centers for Disease Control and Prevention.
- [4]EPA IRIS: 3,3'-Dimethylbenzidine (o‑Tolidine) Toxicological Review/Summary. U.S. Environmental Protection Agency.
- [5]EPA Method 330.5 (DPD colorimetric) for chlorine in water; EPA drinking water methods. U.S. Environmental Protection Agency.