A survey of a small group of workers exposed to toluene di-isocyanate

All 20 workers exposed to toluene di-isocyanate (TDI) in a chemical processing and packing factory were tested for TDI-induced asthma. The assessment included a respiratory symptom questionnaire, spirometry, skin prick tests for common allergens and assessment of total and TDI-specific immunoglobulin E (IgE) levels by radio-allergosorbent tests. Six workers had symptoms suggestive of TDI-related asthma. Three of these 6 workers had a significant cross-shift decline in forced expiratory volume in 1 second (FEV1) (10% or greater). Two of the 6 had high levels of TDI-specific IgE. Of the 14 workers without work-related symptoms, 1 had a significant cross-shift decline in FEV1. There was no significant association between the levels of exposure to TDI and symptoms, lung function parameters or immunological findings. This study demonstrates the difficulties in correlating immunological status with clinical and lung function findings in workers exposed to TDI. Recommendations include a stepwise approach to diagnosing TDI-induced asthma in exposed workers.