Airborne Isocyanates, Aminoisocyanates and Amines

Abstract: Isocyanates are used in the production of polyurethane (PUR). Exposure to isocyanates is associated with respiratory disorders and may occur during production or processing of PUR. During thermal degradation of PUR, amines and aminoisocyanates are formed in addition to isocyanates. Some isocyanates and several aromatic amines are sensitizers and listed as carcinogens. A liquid chromatography mass spectrometry (LC-MS) method for simultaneous determination of isocyanates, aminoisocyanates and amines in gas and particle phase was developed. Air samples were collected in midget impinger flasks, containing di-n-butylamine (DBA) in toluene, and glass fibre filters in series to form specific DBA-isocyanate derivatives. Amines were derivatized with ethyl chloroformate. Derivatives were characterized using both LC-MS and LC-chemiluminescent nitrogen detection. Gas chromatography with MS and thermionic specific detection was also used. LC-MS detection resulted in a highly sensitive measurement of isocyanates equivalent to 1/2000 of the Swedish threshold limit value (for TDI in a 5 L air sample). In air samples from spray painting operations, aliphatic isocyanates that have not been reported previously were revealed. In car repair shops, during work operations such as welding in PUR-coated metal sheets, isocyanates, aminoisocyanates and amines were observed at high concentrations in both gas and particle phase. Compounds with high volatility were efficiently collected in the impinger flask, whereas compounds with low volatility were mainly found on the filter. Isocyanic acid (ICA) and methyl isocyanate (MIC) were among the most dominating compounds present. ICA and MIC could also be observed when urea-based resins were thermally degraded.