Recurrent asthma induced by toluene diisocyanate.

A worker developed toluene diisocyanate induced asthma in 1974. On reassessment, 11 years after leaving the chemical plant where toluene diisocyanate was produced, he had no respiratory symptoms and normal bronchial reactivity in response to methacholine, and showed no reaction when challenged with a subirritant concentration of toluene diisocyanate. He developed asthma within five months of returning to the workplace. Repeat challenge testing showed bronchial hyperreactivity to methacholine and to the specific sensitising agent, toluene diisocyanate. This clinical pattern could be due to underlying toluene diisocyanate sensitivity with resolution and reappearance of hyperresponsiveness to methacholine and toluene diisocyanate reactivity associated with workplace toluene diisocyanate exposure. Alternatively, this worker may have developed sensitisation to toluene diisocyanate anew.