Methanol — biological monitoring
When to suspect: Solvents/cleaners, antifreeze, paint/varnish removers, fuels (washer fluid, model fuel), printing, embalming. CNS / optic-nerve toxicity from formic-acid metabolite.
Urinary methanol (mg/L)
| Level | Interpretation |
|---|---|
| < 5 | Endogenous / non-exposed background |
| 15 | ACGIH BEI — end of shift |
Urinary formic acid is an ancillary marker. Ethanol co-ingestion blocks methanol metabolism (confounds).
Biological exposure index
ACGIH BEI = 15 mg/L urinary methanol, end of shift (TLV-TWA 200 ppm).
Basis: ACGIH BEI.
Sample collection & preparation
- Spot urine, end-of-shift; cap tightly (volatile); headspace GC promptly or freeze.
- Note ethanol co-ingestion; aspartame/fruit raise background.
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