Determination of a new biomarker in subjects exposed to 4,4′-methylenediphenyl diisocyanate

4,4′-Methylenediphenyl diisocyanate (MDI) is the most important of the isocyanates used as intermediates in the chemical industry. Among the main types of damage after exposure to low levels of MDI are lung sensitization and asthma. Albumin adducts of MDI might be involved in the etiology of sensitization reactions. This work presents a liquid chromatography (LC)–mass spectrometry (MS/MS) procedure for determination of isocyanate-specific albumin adducts in humans. MDI formed adducts with lysine of albumin: MDI–Lys and AcMDI–Lys. The MDI–Lys levels, 25th, 50th, 75th, 90th percentile, were 0, 65.2, 134, 244?fmol mg^?1 and 0, 30.5, 57.4, 95.8?fmol mg^?1 in the exposed construction and factory workers, respectively. This new biomonitoring procedure will allow assessment of suspected exposure sources and may contribute to the identification of individuals who are particularly vulnerable for developing bronchial asthma and other respiratory diseases after exposure to isocyanates.