Risk factors for bronchial hyperresponsiveness in workers exposed to acid anhydrides

Risk factors for bronchial hyperresponsiveness have previously been establi shed in the general community. In settings where occupational asthma is a r isk it has not been established whether occupational sensitization or measu res of exposure are important. Bronchial responsiveness to histamine was measured in a cohort of 506 worke rs exposed to acid anhydrides, Skin-prick tests were performed with conjuga tes of phthalic, maleic and trimellitic anhydride with human serum albumin and with common inhalant allergens. Employment and smoking histories were r ecorded. Occupational exposure was measured using personal air samplers and estimates of past exposure made by retrospective exposure assessment. Three hundred and seventy workers (73%) had bronchial responsiveness measur ed (median age 39 yrs, range 18-77) and 46 (12%) of these were hyperrespons ive (provocative dose causing a 20% fall in forced expiratory volume in one second (FEV1: PD20 less than or equal to 8 mu mol), Twelve (3%) of these r esponsive workers had a skin-prick test reaction to an acid anhydride conju gate, 124 (34%) to a common inhalant allergen, and 148 (40%) were current s mokers. Multivariate analysis showed that occupational sensitization, sensi tization to a common inhalant allergen, age, and pack-years of smoking were independent risk factors for bronchial hyperresponsiveness. Of these only occupational sensitization was completely independent of baseline FEV1. It is concluded that sensitization to acid anhydrides is a significant risk factor for bronchial hyperresponsiveness. However, measures of personal ac id anhydride exposure were not associated,vith bronchial hyperresponsivenes s.