Toluene Urine Testing

Solvents & VOCs · Solvents & VOCs overview

Urinary o-cresol is the preferred biomarker for occupational toluene exposure; hippuric acid is retained only where o-cresol is unavailable, because background hippuric acid from dietary benzoate is high and variable.

Biomarker selection

Toluene is metabolised principally to benzyl alcohol and then to benzoic acid, conjugated with glycine to hippuric acid. A small fraction undergoes ring hydroxylation to o-cresol. o-Cresol is specific enough at low workplace exposures to be the preferred biomarker (ACGIH BEI 0.3 mg/g creatinine end-of-shift).

Hippuric acid (ACGIH BEI 1.6 g/g creatinine) is dominated by dietary background (benzoate preservatives in soft drinks, processed food) and is now rarely used as a primary marker.

Sampling timing and method

End-of-shift urine, 60 ml universal container, no preservative, frozen for transport. LC-MS/MS quantification. Sample timing within 30 minutes of last exposure is preferred; samples collected more than two hours after shift end are flagged.

Workplace applications

Print works (toluene-based inks), adhesive manufacture and application, paint thinning, laboratory solvent use, and rotogravure printing. Pair end-of-shift biomonitoring with personal air monitoring for control-route attribution.