Aniline / nitrobenzene (methaemoglobin) — biological monitoring
When to suspect: Aniline & nitrobenzene mfg, dye/pigment & rubber-chemical production, explosives (nitro-aromatics), pesticides, pharma synthesis. Marked dermal absorption.
Blood methaemoglobin · urinary p-aminophenol (% · mg/L)
| Level | Interpretation |
|---|---|
| < 1.5% | Normal background MetHb |
| 1.5% | ACGIH BEI — MetHb, during/end of shift |
| p-AP 50 | ACGIH BEI — total p-aminophenol, end of shift (mg/L) |
Paracetamol/acetaminophen markedly raises urinary p-aminophenol (confounder) — record drug history.
Biological exposure index
ACGIH BEI (methaemoglobin inducers): MetHb 1.5% (during/end of shift); total p-aminophenol 50 mg/L (end of shift).
Basis: ACGIH BEI (Methemoglobin Inducers / Aniline documentation).
Sample collection & preparation
- MetHb: anticoagulated whole blood, full tube, CO-oximetry promptly (MetHb declines on standing).
- p-Aminophenol: spot urine, end-of-shift; record paracetamol use. Both absorb through skin.
Statutory basis. Factories Act 1948 sets only AIR limits (Second Schedule TWA/STEL, s.41F) and mandates the hazardous-process exam (s.41C, ≤12-monthly); it gives NO blood/urine values. The ranges below are ACGIH BEI / OSHA / clinical benchmarks (India has not adopted biological limits into law).
Reference information for occupational-health professionals — not medical advice, and not a substitute for examination by a qualified physician.
All 27 agents — toxicology & biological monitoring
MedFactory — Occupational Health Centre software for Indian factories