A cross-sectional survey of 32 workers exposed to hexahydrophthalic and methylhexahydrophthalic anhydrides

The relation between exposure and sensitization or the appearance of symptoms of the eyes and airways was investigated in a cross-sectional study on 32 workers from a plant using epoxy resin with a mixture of hexahydrophthalic anhydride (HHPA) and methylhexahydrophthalic anhydride (MHHPA) as a hardener. The main component in the hardener was HHPA, and the geometric mean concentrations of HHPA in the workplaces were extremely low (<40 microg/m3) in recent years, compared to the Occupational Exposure Limit-Ceiling for phthalic anhydride (2 mg/m3). However, specific IgE antibody to HHPA was detected in serum from 8 (25%) out of the workers: of those, 5 workers experienced symptoms of the eyes and nose during work (group sensitized symptomatic (SS)) and 3 workers did not (group sensitized nonsymptomatic (SN)). The other 24 workers had no signs of sensitization and did not complain of work-related symptoms. Based on occupational history and anamnestic data, it was concluded that one subject in the SS group and all the subjects in the SN group had been sensitized by higher exposures in the past. The symptoms of 4 subjects in the SS group occurred only when carrying out short-time, particular tasks (15-30 min) a few times a day, such as the resin mixing procedures, manual application of the resin, or opening of ovens. High peak exposures were estimated to have occurred during the particular tasks. Our results suggest that short-time peak exposures may have a great impact on the development of specific IgE or work-related symptoms. Therefore, to minimize the risk of sensitization and work-related symptoms, a reduction of exposure during particular tasks with high peak exposures, along with a decrease in mean 8-h time-weighted average exposure, should be achieved.