Chronic pulmonary function loss from exposure to toluene diisocyanate

Abstract

In 1972 a total of 112 workers exposed to toluene diisocyanate (TDI) were examined for acute pulmonary function changes during a work shift on the first day of the working week. A dose-response relationship was demonstrated for the acute effects of TDI in this population. The cohort was restudied in 1974 to determine whether there was excessive loss of pulmonary function, and if so, whether there was an exposure level below which this did not occur. The original cohort was reduced to 63 workers available for re-survey of which 57 could be assigned reliable personal exposure levels for the two-year study period. Pulmonary function measurements were made again before and after work on the first day of the working week. A total of 132 environmental samples were collected on this and previous occasions during the study period. The 57 workers were divided into three exposure subgroups (≤ 0·0015; 0·0020 - 0·0030; ≥ 0·0035 ppm). Using the FEV1·0 as a measure of response, a dose-response relationship was observed. Only those in the lowest exposure subgroup showed normal two-year declines. The FEV1·0 of those in the highest exposure group fell 206 ml in two years (103 ml/year) which exceeds the expected value by three- to fourfold. The decrement of FEV1·0 in the middle exposure group was borderline (42 ml/year). These differences in FEV1·0 by exposure subgroup were not explained by age, months employed, smoking habits, or variables related to lung size. A significant association (r = 0·35, p < 0·005) between acute and chronic decrement in FEV1·0 was shown again. We conclude that chronic occupational exposure to TDI at 0·003 ppm or higher is unsafe.