The outcome of asthma related to workplace irritant exposures - A comparison of irritant-induced asthma and irritant aggravation of asthma

Study objectives: (1) To characterize workers' compensation claims accepted on the basis of new-onset asthma associated with accidental high respirato ry irritant exposure at work: (2) to compare the frequency, characteristics , and outcomes in this group of workers to workers who were compensated for an exacerbation of preexisting asthma associated with accidental high resp iratory irritant exposure at work. Design: A retrospective review was performed of 469 asthma claims accepted by the Ontario Workers' Compensation Board (WCB) between 1984 and 1988. Amo ng these, claims attributed to an accidental high respiratory irritant expo sure at work were classified into two groups: one group with reported preex isting asthma prior to the exposure (accidental aggravation of asthma [AAA] ) and another group with no previous history of asthma (irritant-induced as thma [IIA]). Results: Of the 469 claims, 89 subjects (19%) had symptoms related to accid ental high respiratory irritant exposure in the workplace; of these, 68 sub jects (76%) had AAA, 12 subjects (13%) had IIA, and 9 subjects (10%) had po ssible IIA but were excluded from the analysis because of insufficient data , Those with IIA had a longer duration of work-attributed symptoms (mean, 2 19 +/- 208 days) than the subjects with AAA, (mean, 32 +/- 38 days; p < 0.0 01). Nine subjects (75%) with IIA were no longer in the same work environme nt, while 47 subjects in the AAA group (71%) were still in the same work en vironment (p < 0.001). The most common triggering agent for subjects with I IA was an isocyanate spill; for those with AAA, the most common triggering agent nas paint, Conclusions: The WCB-accepted claims related to accidental, high respirator y irritant exposure at work are more commonly assigned to the category of A AA than to IIA. IIA patients in this claimant group had a longer mean durat ion of work-attributed respiratory symptoms, perhaps due to a need for a la rger (and thus less common) irritant exposure to induce asthma in previousl y normal subjects.