Determination of albumin adducts of 4,4′-methylenediphenyl diisocyanate after specific inhalative challenge tests in workers

- Lung sensitization with bronchial asthma is the main disorder in workers exposed to 4,4′-methylenediphenyl diisocyanate (MDI).
- MDI-Lys is an isocyanate-specific adduct of MDI with albumin.
- We found MDI-adducts in workers undergoing diagnostic MDI challenge tests.
- The adduct levels increase significantly after the exposure to MDI in the challenge chamber.
- About 0.6% of the dose was bound to albumin.

4,4′-Methylenediphenyl diisocyanate (MDI) is the most important isocyanate used in the industry. Lung sensitization with bronchial asthma is the main disorder in exposed workers. Albumin adducts of MDI might be involved in specific immunological reactions. MDI adducts with lysine (MDI-Lys) of albumin have been found in MDI-workers and construction workers. MDI-Lys is an isocyanate-specific adduct of MDI with albumin. In the present study, we report MDI-adducts in workers undergoing diagnostic MDI challenge tests. The workers were exposed for 2 h to 5 ppb of MDI. The adduct levels increase significantly after the exposure to MDI in the challenge chamber. About 0.6% of the dose was bound to albumin. So far, only urinary metabolites of MDI were measured to monitor isocyanate workers. However, such urinary metabolites are not isocyanate specific. Therefore, we propose to measure albumin adducts for monitoring MDI exposed subjects.