Longitudinal changes in pulmonary function and respiratory symptoms in cotton textile workers - A 15-yr follow-up study

To evaluate the chronic effects of exposure to cotton dust, a 15-yr follow- up study in cotton textile workers was performed in Shanghai, China from 19 81 to 1996. Testing occurred four times during the 15-yr period. The achiev ed follow-up rates were 76-88% of the original 447 cotton textile workers, and 70-85% of the original 472 silk textile workers (as a control group). I dentical questionnaires, equipment, and methods were used throughout the st udy. The prevalence of byssinosis increased over time in cotton workers, wi th 15.3% at the last survey versus 7.6% at the baseline, whereas no byssino sis was found in silk workers. More workers in the cotton group consistentl y reported symptoms than in the silk group, although symptom reporting vari ed considerably from survey to survey. Cotton workers had small, but signif icantly greater, adjusted annual declines in FEV1 and FVC than did the silk workers. Years worked in cotton mills, high level of exposure to endotoxin , and across-shift drops in FEV1 were found to be significant determinants for longitudinal change in FEV1, after controlling for appropriate confound ers. Furthermore, there were statistically significant associations between excessive loss of FEV1 and byssinosis, chest tightness at work, and chroni c bronchitis in cotton workers. Workers who consistently (three or four of the surveys) reported byssinosis or chest tightness at work had a significa ntly greater 15-yr loss of FEV1. We conclude that long-term exposure to cot ton dust is associated with chronic or permanent obstructive impairments. C onsistent reporting of respiratory symptoms, including byssinosis and chest tightness at work is of value to predict the magnitude and severity of chr onic impairments in textile workers.