Non-specific bronchial hyper-reactivity in workers exposed to toluene di-isocyanate, diphenyl methane di-isocyanate and colophony.

Non-specific bronchial reactivity to histamine has been measured before specific occupational bronchial tests in the following groups: 51 workers exposed to toluene di-isocyanate (TDI); 40 workers exposed to diphenylmethane diisocyanate (MDI); 45 electronics workers exposed to colophony fumes and 13 unexposed controls. Finally 38 electronics workers had repeated measurements after moving their place of work. The results showed that histamine reactivity was an important, but not obligatory, factor in the development of occupational asthma, and that it appeared to be the result rather than the cause of occupational asthma, as it returned towards normal in workers removed from exposure. TDI and MDI were shown to be acting as specific causes of occupational asthma rather than nonspecific irritants at concentrations up to 0.02 ppm. There was evidence that some irritant reactions to colophony were occurring at exposure levels encountered at work, but that the majority of workers with colophony asthma were having specific reactions to the colophony fume.