Distinguishing byssinosis from chronic obstructive pulmonary disease. Results of a prospective five-year study of cotton mill workers in India.

This prospective 5-yr follow-up study of 1,241 textile workers from three mills was designed to determine the pattern and course of byssinosis in India and to distinguish this disease from chronic bronchitis. The initial prevalence of byssinosis was 14% in carding sections, 10% in spinning sections, and 11% in winding sections. In these dusty sections, the prevalences of both byssinosis and bronchitis increased with a longer service. Among workers with byssinosis; 56% had work-related and exertional dyspnea, 54% had chest tightness, 20% had wheezing, and 36% had cough. There was a history of Monday sickness in 22%. During follow-up it was confirmed that the atypical presentation of byssinosis with cough was more common in the carding department. The yearly decrease in pulmonary function was correlated with duration and degree of exposure to cotton dust. Thus, the decrease was larger in carding workers and in workers with byssinosis plus cough than in those with byssinosis or bronchitis. The yearly decrease in the one-second forced expiratory volume was different (p less than 0.05) for subjects with nonspecific chest symptoms (88 ml) and subjects with work-related chest symptoms (114 ml). The decreases in forced vital capacity and one-second forced expiratory volume were larger for increased dust loads. Fewer pulmonary infiltrates were seen in radiographs of workers with byssinosis than in those of workers with bronchitis. The immunoglobulins studied in 86 textiles workers and 17 control subjects showed higher IgG values among workers with work-related symptoms, especially cough, but not among those with bronchitic symptoms (p less than 0.01). Our results suggested that byssinosis is an entity distinct from chronic bronchitis.