Biological monitoring of n-hexane exposure in Portuguese shoe manufacturing workers.

Occupational risk of exposure to organic solvents concerned many shoe manufacturing workers. The most common organic solvents found in workplace environments were n-hexane and others hexane isomers. The aim of this study was to evaluate the exposure of shoe manufacturing workers to n-hexane, with 2,5 hexanedione in urine (2,5HD) as a biomarker and to investigate effect in 2,5 HD excretion of the co-exposure to other organic solvents. Post-shift urine samples from workers who performed gluing tasks (n = 45) in five shoe manufacturers were collected, as well as urine samples from a similar number of unexposed controls (n = 51) in the same factories. 2,5 HD was measured by capillary gas chromatography. Air monitoring of organic solvents in the workplaces was performed and the compounds were analyzed by gas chromatography. Significant more 2,5 HD was found in the urine of personnel who performed gluing tasks than in the unexposed workers. A significant correlation was observed between n-hexane exposure and urinary 2,5 HD, with a high correlation coefficient. Multiple regression analysis indicated that n-hexane exposure and co-exposure to others solvents were significant predictors of the concentration of 2,5 HD. Co-exposure led to higher urinary 2,5 HD concentrations. The significant effect of co-exposure reinforces the interest of biological monitoring for n-hexane exposure evaluation. In case of multiple exposures, biological monitoring can be a better predictive measurement for early detection of n-hexane neurotoxic lesions than air monitoring data.