AIRWAY HYPERRESPONSIVENESS, PREVALENCE OF CHRONIC RESPIRATORY SYMPTOMS, AND LUNG-FUNCTION IN WORKERS EXPOSED TO IRRITANTS

The association between occupational exposure to airway irritants and the prevalence of chronic respiratory symptoms and level of lung funct ion, and whether these associations were modified by airway hyperrespo nsiveness, smoking, and a history of allergy were studied in 668 worke rs from synthetic fibre plants. Respiratory symptoms were recorded wit h a self administered Dutch version of the British Medical Research Co uncil questionnaire, with additional questions on allergy. Airway resp onsiveness was measured by a 30 second tidal breathing histamine chall enge test. On the basis of job titles and working department, the curr ent state of exposure of an workers was characterised as (1) no exposu re, reference group; (2) white collar workers; (3) SO2 HCl, SO42: (4) polyester vapour; (5) oil mist and vapour; (6) polyamide and polyester vapour; (7) multiple exposure. Workers exposed to airway irritants we re not simultaneously exposed to airborne dust. Airway hyperresponsive ness (AHR), defined as a 20% fall in forced expiratory volume in one s econd (FEV1) at less-than-or-equal-to 32 mg/ml histamine, was present in 23% of the subjects. The association between exposure groups and pr evalence of symptoms was estimated by means of multiple logistic regre ssion; the association with level of lung function (forced vital capac ity (FVC), FEV1, maximum mid-expiratory flow rate (MMEF)) was estimate d by means of multiple linear regression. Both methods allow simultane ous adjustment for potential confounding factors. The exposure groups were associated with a higher prevalence of chronic respiratory sympto ms. Lower prevalence of symptoms was found for workers exposed to SO2, HCl, and SO42-, most likely due to pre-employment selection procedure s. Current smoking, AHR, and a history of allergy were significantly a ssociated with a higher prevalence of chronic respiratory symptoms, in dependent of each other, and independent of irritant exposure. The ass ociation between exposure and prevalence of symptoms was greater in sm okers than in ex-smokers and non-smokers. This difference was most cle arly seen in the polyester vapour and polyamide and polyester vapour g roup. No modification of the association between exposure groups and p revalence of symptoms by airway hyperresponsiveness could be shown. Th e exposure groups were not significantly associated with a lower level of lung function. Adjustment for chronic respiratory symptoms did not change the results. There were no indications of a possible interacti on between exposure and AHR, current smoking, or a history of allergy on lung function. Workers of the polyester vapour and the oil mist and vapour group with >10 years of exposure had a lower FEV1 (beta = -295 and -358 ml) and a significantly lower MMEF (beta = - 1080 and -1247 ml/s; p < 0.05) than the reference group. The number of workers of bot h groups were, however, small (n = 10 and n = 13 respectively). More i nvestigation is needed to clarify the relations between low level expo sure to irritant and respiratory health.