Biomonitoring of 2,4'-methylene diphenyldianiline for assessment of exposure to methylene diphenyl diisocyanate aerosol

The exposure to methylene diphenyl diisocyanate (MDI) aerosol was investigated by biomnitoring of 2,4'-methylene diphenyldianiline (MDA) in urines of exposed workers. Biological monitoring was done for its metabolite by the analysis of isocyanate-derived diamines released from protein adducts in urine or plasma by GC-MS. The urine samples, at the end of working shifts of polyurethane factory, were collected in polystyrene bottles containing 10 g citric acid, and stored at 4 °C until analysis. The mean concentration values of MDA in the five selected factories were in the range of 3.01 to 3.58 µmol/mol creatinine for all subjects and the highest mean value of MDI concentration was 99 µg/m³ from indoor air samples analysis. The results show a linear relationship between MDI and MDA concentrations with a value of R2=0.801 (P<0.05). This study demonstrates that not only urinary MDA is detectable following diisocyanates aerosol exposure but also it is likely to be a useful practical biomarker to monitor diisocyanates exposure in the workplaces or for the epidemiologic studies.