Dose-response of Cotton Dust Exposure with Lung Function among Textile Workers: MultiTex Study in Karachi, Pakistan

Background: Cotton dust exposure among textile mill workers lead to impaired lung function. However, only few studies have investigated the dose-response relationship between cotton dust and lung function. Objective: To determine the dose-response relationship between cotton dust exposure and lung function among textile workers. Methods: This cross-sectional survey was conducted from January to March 2016 and included 303 adult male textile workers from spinning and weaving sections of 5 mills in Karachi, Pakistan. We collected data through a translated version of the American Thoracic Society respiratory questionnaire (ATS-DLD-78A) and using spirometry. Mill-level airborne cotton dust was measured over an 8-12-hour shift through UCB-PATS (University of California, Berkeley-Particle, and Temperature Monitoring System). Multiple linear regression was used to determine the association between cotton dust exposure and lung function assessed through the 3 indices: forced expiratory volume in the first second (FEV1), forced vital capacity (FVC), and their ratio (FEV1/FVC). Results: The mean age of the workers was 32.5 (SD 10.5) years. The mean spirometry indices expressed in percent predicted values were FEV1 82.6 (SD 14.0); FVC 90.3 (14.7), and FEV1/FVC 94.9 (10.5). The median cotton dust concentration was 0.61 (IQR 0.2 to 1.3) mg/m(3). The frequency of respiratory symptoms was 15% for cough, 20% for phlegm, and 20% for wheezing. After adjustment for covariates, every mg/m(3) increase in dust concentration was associated with 5.4% decline in FEV1. Conclusion: This study quantifies the exposure-dependent relationship between cotton dust and lung function; which has implications for regulations and standards in the textile industry in Pakistan and similar cotton-processing countries.