Effect of respiratory protective devices on development of antibody and occupational asthma to an acid anhydride

Study objectives: To determine whether the use of respiratory protective equipment would reduce the incidence of occupational asthma due to exposure to hexahydrophthalic anhydride (HHPA). Design: Prospective cohort study. Setting: A facility that makes an epoxy resin product requiring HHPA for its manufacture. Participants: Sixty-six individuals newly hired at a facility that makes an epoxy resin product requiring HHPA for its manufacture. Intervention: Employees who wished to use respiratory protective equipment could choose from three types of masks: dust mask, half-face organic vapor respirator, or full-face organic vapor respirator. Measurements: Workers were evaluated annually for development of positive antibody to HHPA and occupational, immunologic respiratory disease, including occupational asthma. Results: With use of respiratory protective equipment, the rate of developing an occupational immunologic respiratory disease was reduced from approximately 10 to 2% per year. Occupational asthma developed in only three individuals, and they were all in the higher exposure category. Statistically, one respirator was not superior to the others. Conclusion: Respiratory protective equipment can reduce the incidence of occupational immunologic respiratory disease, including occupational asthma, in employees exposed to HHPA.