CHRONIC-BRONCHITIS IN TEXTILE WORKERS

Background-Exposure to cotton is known to produce a specific occupatio nal disease known as byssinosis. A large population of textile workers was investigated to determine whether such exposure was also associat ed with chronic bronchitis once other possible aetiological factors ha d been accounted for. Methods-A total of 2991 workers were investigate d for the presence of symptoms compatible with chronic bronchitis. An MRC adapted respiratory questionnaire and MRC definition of chronic br onchitis were used for diagnostic labelling. Current and Lifetime expo sure to dust was estimated by personal and work area sampling, and the use of records of retrospective dust levels previously measured over the preceding 10 years. Airborne endotoxin exposure was measured using a quantitative turbidometric assay. Lung function tests were performe d to measure forced expiratory volume in one second (FEV(1)) and force d vital capacity (FVC). A control group of workers exposed to manmade fibre textiles was identified. The comparative prevalence of chronic b ronchitis in the two populations was assessed, allowing for sex, age, smoking habit, and ethnic origin. Two case referent studies were also performed; cases of chronic bronchitis were separately matched with co ntrols from the cotton and control populations to determine the effect of the symptomatic state on lung function. Results-After controlling for smoking (pack years), workers in a cotton environment were signifi cantly more likely to suffer from chronic bronchitis and this was most marked in workers over 45 years of age (odds ratio 2.51 (CI 1.3 to 4. 9); p<0.01). Regression analysis of all possible influencing parameter s showed that cumulative exposure to cotton dust was significantly ass ociated with chronic bronchitis after the effects of age, sex, smoking , and ethnic group were accounted for (p<0.0005). In the intra-cotton population case control study a diagnosis of chronic bronchitis was as sociated with a small decrement in lung function compared with control s: percentage predicted FEV(1) in cases 81.4% (95% CI 78.3 to 84.6), c ontrols 86.7% (84.9 to 88.5); FVC in cases 89.9% (95% CI 87.0 to 92.9) , controls 94.6% (92.8 to 96.4). After controlling for cumulative past exposure and pack years of smoking the effect of the diagnostic state remained significant for both FEV(1) (p<0.01) and FVC (p<0.05). Concl usions-Chronic bronchitis is more prevalent in cotton workers than in those working with man-made fibre and exposure is additive to the effe ct of smoking. The diagnosis of chronic bronchitis is associated with a small but significant decrement in lung function.