Two-year observation of pulmonary function in workers exposed to low concentrations of toluene diisocyanate

Pulmonary effects were investigated in 106 toluene diisocyanate (TDI)-exposed workers and 39 referents in 64 exposed workers and 21 referents on the 2-year follow-up study in 1982. Means of individual, time-weighted average (TWA) exposure concentrations measured by personal monitors were approximately 0.001 ppm in each year. Short-term exposure at 0.02 ppm or over was observed in 9.3% of the collected samples in 1980 and 1.9% in 1982. Pulmonary function was assessed by measurements of maximum expiratory flow-volume curve and respiratory impedance. No differences were observed in the means of the pulmonary functions and their individual daily changes between the TDI workers and the referents. Significant intra-individual, two-year decreases were observed in some pulmonary function parameters in both groups, but when the effect of aging was adjusted, the decreases disappeared. Prevalences of respiratory symptoms in the TDI workers were not significantly higher than those in the referents, except for irritating complaints of the eyes and throat probably due to peak exposure to TDI and/or co-existing irritants. Eight of the TDI workers had episodes of acute asthmatic reactions shortly after having begun their TDI jobs and most parameters in their maximum expiratory flow were significantly less than the predicted values, though exposure concentrations when the episodes occurred could not be defined. From these results, it was suggested that TDI exposure at the levels of 0.001 ppm may not induce adverse pulmonary effects when the workers are not hypersusceptive to TDI.