Comparison between urinary o-cresol and toluene as biomarkers for assessing toluene exposure

Aim: In the present research the characteristics of urinary o-cresol and toluene as biomarkers of exposure to toluene were comparatively evaluated. Methods: 100 healthy male rotogravure-printing workers (P) and 87 male and female control subjects (C) were investigated. Personal exposure to toluene during the shift was determined. Simple and sensible analytical procedures based on solid phase micro-extraction followed by GC/MS analysis were developed and applied to the determination of end-shift urinary o-cresol and toluene. Results: Median exposure to airborne toluene, as time weighted average, was 48 (in the range 6-162) mg/m3 in P and 0.03 (0.01-0.14) mg/m3 in C. o-Cresol was 0.19 (0.03-0.95) mg/g creatinine in P and 0.03 (0.002-0.330) mg/g creatinine in C. Urinary toluene was 8 (2-24) µg/l in P and <1 µg/l in C. Accordingly with all indices, exposure to toluene was higher in P than in C. Nevertheless the distributions of o-cresol in the two groups were partially overlapped, whereas such behaviour was not found in urinary toluene. Both urinary o-cresol and toluene were correlated with personal exposure (Pearson r 0.64 and 0.82 respectively) and among them. Smoking habit significantly increased the excretion of o-cresol, but not of toluene. Conclusion: Urinary toluene, although presents constrains in sample handling and sampling time, has low background values, is not affected by smoking habit, has lower inter-individual variability, higher specificity and sensitivity in comparison with o-cresol; for such reasons we recommend its use as biomarker of short term exposure to toluene.