Airway hyperresponsiveness in workers exposed to low levels of irritants.

The purpose of this study was to assess the association between occupational exposure to low levels of airway irritants, and airway responsiveness to histamine. In 688 male workers, symptom prevalence was assessed according to the British Medical Research Council (BMRC) questionnaire. All subjects performed a 30 s tidal breathing challenge test. Airway hyperresponsiveness (AHR) was defined as a 20% fall in forced expiratory volume in one second (FEV1) at < or = 32 mg.ml-1 histamine. On the basis of job titles and working department, the exposure status of all workers was characterized into seven groups: 1) reference group; 2) white collars; 3) SO2, HCl, SO4(2-); 4) polyester vapour; 5) oil mist and oil vapour; 6) polyamide and polyester vapour; and 7) multiple exposures. Using multiple logistic regression, no association was found between the exposure groups and a higher prevalence of AHR. A higher prevalence was significantly associated with a low FEV1, a history of allergy, and the presence of chronic respiratory symptoms. Subjects in the SO2 group and the oil mist group with < or = 5 exposure years had a lower prevalence of AHR, probably due to pre-employment selection procedures. There was some trend for subjects with more than 5 yrs exposure to polyester vapour and to oil mist and to oil vapour to have a higher prevalence of AHR. Analyses using the dose-response slope according to O'Connor, revealed similar results and provides no additional information. We conclude that no association could be demonstrated between low grade exposure to airway irritants and airway hyperresponsiveness, and that further research is needed to elucidate this relationship.