Evaluation of environmental and biological monitoring methods for toluene exposure assessment in paint industry

Abstract

The aim of this study was to assess the exposure to Toluene in paint industry and to evaluate the environmental and biological monitoring techniques for the assessment of occupational exposure to this aromatic hydrocarbon. In this study, personal active and passive air sampling for toluene measurements, blood and urine sampling respectively for B-Tol and HA or U-Tol analyses for eight workers from two paint and thinner production factories were collected during four successive working days. Correlations were analyzed between biological indicators and environmental toluene exposure levels. The concentration of Toluene measured in air samples ranged from 0.2 to 414.0 ppm (mean = 59.8 ppm), with high variability of atmospheric levels between activities and between days. No significant difference was found between airborne toluene concentrations measured by the two sampling methods. The correlation between air concentrations sampled by the diffusive sampling method and the biomarkers was the best for HA (r = 0.902, p < 0.01), followed by B-Tol (r = 0.820; p < 0.01), o-Cr (r = 0.691; p < 0.01) and U-Tol (r = 0.607; p < 0.05). The correlation was better between air concentrations and urinary metabolites HA and o-Cr for exposure levels higher than 50 ppm (r = 0.931; p < 0.01), and lower than 300 ppm (r = 0.827; p < 0.01), respectively. According to our results, workers in the studied industries are highly exposed to Toluene. Given the high correlation found between toluene concentrations in samples taken on dosimeters and those actively sampled on charcoal tubes, it may be assumed that both sampling methods are valuable. Despite the influencing factors, HA was found to be a reliable biological indicator for the monitoring of occupational exposure to toluene for high exposure levels. However, B-Tol seems to be an interesting alternative, since it is more specific and showed the best correlations with airborne toluene levels.

Keywords: Biomonitoring, blood; Hippuric acid; Occupational exposure; Paint; Toluene; Urine; ortho-Cresol.

Fig. 1

Day to day variation of toluene concentrations in air samples sampled by (A) passive sampling and (B) by active sampling methods.

Fig. 2

Correlation between toluene concentrations in air samples sampled by passive sampling (Tol P) and by active sampling methods (Tol A). The inner bounds show 95.0% confidence limits for the mean Tol P of many observations at given values of Tol A. The outer bounds show 95.0% prediction limits for new observations.

Fig. 3

Toluene concentrations in air samples sampled by passive and by active sampling methods.

Fig. 4

Correlation between toluene concentrations (passive sampling) < 50 ppm (A) and greater than 50 ppm (B) with urinary HA concentrations. The inner bounds show 95.0 % confidence limits for the mean Tol P of many observations at given values of HA. The outer bounds show 95.0 % prediction limits for new observations.

Fig. 5

Correlation between all toluene concentrations (passive sampling) (A) and < 300 ppm (B) with urinary o-Cr concentrations. The inner bounds show 95.0 % confidence limits for the mean Tol P of many observations at given values of o-Cr. The outer bounds show 95.0 % prediction limits for new observations.

Fig. 6

Correlation between toluene concentrations (passive sampling) with B-Tol (A) and with U-Tol (B) concentrations. The inner bounds show 95.0% confidence limits for the mean Tol P of many observations at given values of B-Tol or U-Tol. The outer bounds show 95.0% prediction limits for new observations.