5-YEAR LONGITUDINAL-STUDY OF WORKERS EMPLOYED IN A NEW TOLUENE DIISOCYANATE MANUFACTURING PLANT

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Abstract
The respiratory health of 277 workers in a new toluene diisocyanate (TDI) manufacturing plant was studied prospectively during 5 yr of exposure. Personal TDI monitors were used to continuously measure peak and 8-h time-weighted average (TWA) concentrations in > 2000 samples. Longitudinal change in pulmonary function was assessed in 223 men, in whom .gtoreq. 3 data points allowed construction of individual slopes of annual change. Regression of annual change on smoking (pack-years), atopic status and cumulative TDI exposure, dichotomized at 68.2 ppb mo. into low and high exposure groups, showed significant effects of smoking on spirometric tests and lung volumes. After adjusting for pack-years of smoking, the 74 men in the high cumulative TDI exposure category had significantly larger declines in FEV1 [1-s forced expiratory volume], %FEV [percent forced expiratory volume] and FEF25-75% [forced expiratory fraction from 25 to 75% vital capacity] than did the 149 men in the low category. Annual change in FEV1 was then examined in 6 smoking-exposure categories: in never-smokers, average annual decline was 38 ml/yr greater in those with higher cumulative TDI exposure. Current and previous cigarette smokers did not show this effect of cumulative TDI exposure. Analysis of FEV1 change by time for values .gtoreq. 20 ppb TDI yielded a similar result in never-smokers, a 24 ml/yr excess average decline attributable to longer time > 20 ppb. In current cigarette smokers, those with longer time > 20 ppb had excess decline of 18 ml/yr (42 vs. 24 ml/yr). Low and high cumulative exposure groups spent 2 and 15%, respectively, of their working time > 5 ppb TDI. The different health effects observed in these groups supports the NIOSH[USA National Institute of Occupational Safety and Health]-recommended standard of 5 ppb TDI as an 8-h TWA.

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