Persistence of Toluene Diisocyanate-Induced Asthma Despite Negligible Workplace Exposures: RESULTS part 2
Changes in bronchial responsiveness over time are plotted in Figure 2. All six had bronchial hyperres- ponsiveness to methacholine with PD20 FEV1 less than 30 cumulative methacholine units. Resolution of bronchial hyperresponsiveness to methacholine was not measured in any of these six workers.
FIGURE 2. This figure plots bronchial hyperresponsiveness (PD20 FEV,) by year for each of the six asthmatic subjects. Worker 1 is denoted by an open circle; worker 2 by an open triangle; worker 3 by an open square; worker 4 by a solid square; worker 5 by a solid triangle; and worker 6 by a solid circle. Not all workers performed methacholine testing each year.
Eleven TDI personal samples were obtained in these six asthmatic subjects from 1982 to 1986. Three shifts were monitored for two workers, two shifts for one worker and one shift was monitored for the remaining three workers. For the 94 12-minute increments of exposure, 84 (88 percent) were 1.0 ppb or less and detectable only 35 percent of the time. Mean and SD for the 11 TWA concentrations was 0.64 ± 0.46 ppb, with the TWA of only one of the 11 shifts sampled exceeding 1.0 ppb. In that case, exposure exceeded 5 ppb for 13 percent of the sampling period (an exposure of 6.4 ppb).
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For 49 foam line workers, TDI exposures during 89 shift-long samples (920 12-minute samples) were measured. Mean± SD TWA was 3.82 ±5.51 ppb. For 132 finishing workers, mean±SD TWA was 1.35 ±1.03 ppb for 236 shift-long measurements (2,308 12-minute samples). Mean exposures for the foam line and finishing workers differed significantly (p<0.01) from those of the six asthmatic subjects.
FIGURE 3. Distribution of short-term (12-minute) exposures to TDI among the foam line workers, finishing workers, and asthmatic subjects. A reflects the percentage of samples with a TDI concen-tration above the lower limit of detection. В reflects the percentage of samples with a TDI concentration greater than 5 ppb. С reflects the percentage of samples with a TDI concentration greater than 20 ppb.
Figure 3 illustrates the distribution of the short- term (12-minute) TDI exposure samples by group of workers. These samples were categorized by percentage above the lower limit of detection, greater than 5 ppb and greater than 20 ppb, and show differences in exposure in these groups by these categories. viagra 50 mg