Trends in Pulmonary Function and Prevalence of Asthma in Hexamethylene Diisocyanate Workers During a 19-Year Period

OBJECTIVE: To identify if 1,6-hexamethylene diisocyanate (HDI) workers demonstrated an increased prevalence of occupational asthma or accelerated decline in pulmonary function. METHODS: Employees from two plants manufacturing or producing 1,6-HDI monomer and/or HDI polyisocyanates were matched to a control population by age, gender, race, and smoking status. A random coefficient regression analysis compared the decline in pulmonary function test values over time. Retrospective medical review was used to identify potential cases of occupationally induced asthma. RESULTS: No significantly accelerated annual decline in force expiratory volume after 1 second in the HDI exposure group compared to the matched control group was observed. No cases of adult onset asthma, beyond those present at time of hire, and no cases of occupational asthma were identified. CONCLUSIONS: This study provides support for the current American Conference of Governmental Industrial Hygienists threshold limit value time-weighted average of 5 ppb.