Introduction: methyl diphenyl diisocyanate (MDI) is one of the most commonly iisocyanate used in the foam manufacturing companies. The aim of this study is to evaluat iisocyanate (MDI) effects on the pulmonary capacities of workers by examining the results of workers spirometers in foam.

Methods: This is a cross-sectional study. Sampling was conducted through census company method. In order to investigate the changes of respiratory capacity in the workers. The information of the medical workers records and the spirometry test results in different two years were determined as well as the level of air pollution in the production units using sampling method using descriptive statistics, paired T-test and linear regression analysis, the data were analyzed.

Result: The level of air pollution in the production line of cold foams, and the viscose hall, unit L90 was higher than the maximum allowable (51 microgram/m³). The results of evaluation the respiratory capacity in some workers that expose to MDI, according to work experience more than 3 years, showed that the respiratory capacity of spirometry in 2012 was decreased compared to 2010 (p<0/05). The studied respiratory capacity (FEV1/ FVC) indicated the reduction in these during 2010 to 2012 parameters and on average, FEV1(15.60%) and FVC (9.7%) was reduced.

Conclusion: With increasing the work experience and increasing the duration of exposure to combinations of MDI, workers, respiratory capacity will have been declining and in the long term it might have uncontrollable conditions.