Increase in airway hyperresponsiveness among workers exposed to methylene diphenyldiisocyanate compared to workers exposed to toluene diisocyanate at a petrochemical plant in Korea.

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The purpose of this study was to investigate the prevalence of airway hyperresponsiveness induced by methylene diphenyldiisocyanate (MDI) and toluene diisocyanate (TDI) at a petrochemical industry complex in Korea. Questionnaires, allergic skin test, and nonspecific airway hyperresponsiveness (AHR) were studied in 64 exposed workers and 27 control subjects. Questionnaires included questions about symptoms of cough, wheezing, chest tightness, dyspnea, rhinorrhea, sneezing, itching, stuffiness, tearing, urticaria, sore throat, and exacerbating time. Methacholine challenge tests were done. Bronchial responsiveness (BRindex) defined as log (% fall in FEV(1))/log (last concentration of methacholine +10). Prevalence of AHR (PC20 FEV(1) < 16.0 mg/mL of methacholine) was higher in MDI-exposed workers than in TDI-exposed workers [4/20 (20%) vs. 2/42 (4.7%), P<0.05]. Twenty-three workers (36%) of all subjects had respiratory symptoms. MDI-exposed workers, in comparison with control subjects, had higher BRindex (0.73+/-0.04 vs. 0.62+/-0.02, P<0.05). Workers exposed to TDI or MDI who had respiratory symptoms (n = 23), in comparison to workers exposed to TDI or MDI without respiratory symptoms (n = 41), had significantly higher BRindex (0.82+/-0.06 vs. 0.60+/-0.02, P<0.05). FEV(1) was significantly negatively correlated with BRindex (r = -0.253, P<0.05). BRindex was not correlated with atopy, smoking status, and exposure duration. These findings suggest that workers exposed to MDI are at a higher risk of asthma in comparison with TDI-exposed workers and control subjects at a petrochemical plant in Korea.