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Summary In sixty‐three workers exposed to toluene di‐isocyanate (TDI), no overall differences in bronchial reactivity to histamine inhalation and to exercise testing were found between the total groups of positive and negative TDI reactors to provocation tests. A subgroup of TDI highly sensitive subjects reacting to very low concentrations (≤0.001 p.p.m.) were more sensitive to both histamine and exercise than the group who were less sensitive to TDI, and who reacted to higher concentrations (0.002–0.02 p.p.m.) than the group of non‐reactors. There were, however, in the last group a number of subjects with high degrees of histamine reactivity who did not react to the TDI. These findings suggest that, on the one hand, the asthmatic reactions to TDI cannot be attributed solely to non‐specific mechanisms and, on the other, that in subjects with high degrees of specific sensitivity non‐specific mechanisms may also be playing a part.

Four patients with occupational asthma associated with exposure to soldering flux or hot-melt glue containing pine resin (colophony) were subjected to occupational type inhalation challenge testing.All four gave immediate bronchial reactions to inhalation ofthe fumes, varying from one breath to 3 min of exposure.The clinical history and provocation test reactions suggest hypersensitivity to colophony futnes.

Summary Six workers with a diagnosis of occupational asthma and one with chronic bronchitis were examined for sensitivity to epoxy resin systems and certain of their components. In six cases the chemical agent responsible for their symptoms was identified by careful inhalation challenge testing, simulating their exposure at work and thus providing a precise aetiological diagnosis. In one worker asthma followed exposure to triethylene tetramine fume; four were sensitive to acid anhydrides, three to phthalic acid anhydride as a fume or powder and one to trimellitic anhydride. One worker thought to be sensitive to toluene di‐isocyanate gave negative reactions to this and positive reactions to a phthalic acid anhydride epoxy resin and another thought to have asthma from acid anhydride fumes was found to be sensitive only to toluene di‐isocyanate. Immediate, non‐immediate or combined asthmatic reactions were elicited.

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