Ambient Air Pollution and Chronic Bronchitis in a Cohort of US Women

BACKGROUND: Limited evidence links air pollution exposure to chronic cough and sputum production Few reports have investigated the association between long-term exposure to air pollution and classically defined chronic bronchitis. OBJECTIVES: Our objective was to estimate the association between long-term exposure to particulate matter (diameter <10 mu m, PM10; <2.5 mu m, PM2.5), nitrogen dioxide (NO2). and both incident and prevalent chronic bronchitis. METHODS: We estimated annual average PM2.5, PM10, and NO2 concentrations using a national land-use regression model with spatial smoothing at home addresses of participants in a prospective nationwide U.S. cohort study of sisters of women with breast cancer. Incident chronic bronchitis and prevalent chronic bronchitis, cough and phlegm, were assessed by questionnaires. RESULTS: Among 47,357 individuals with complete data, 1,383 had prevalent chronic bronchitis at baseline, and 647 incident cases occurred over 5.7-y average follow-up. No associations with incident chronic bronchitis were observed. Prevalent chronic bronchitis was associated with PM10 [adjusted odds ratio (aOR) per interquartile range (IQR) difference (5.8 mu g/m(3)) = 1.07; 95% confidence interval (CD: 1.01, 1.13]. In never-smokers, PM2.5 was associated with prevalent chronic bronchitis (aOR = 1.18 per IQR difference; 95% CI: 1.04, 1.34), and NO2 was associated with prevalent chronic bronchitis (aOR = 1.10; 95% CI = 1.01, 1.20), cough (aOR = 1.10; 95% CI: 1.05, 1.16), and phlegm (aOR = 1.07; 95% CI: 1.01, 1.14); interaction p-values (nonsmokers vs. smokers) <0.05. CONCLUSIONS: PM10 exposure was related to chronic bronchitis prevalence. Among never-smokers, PM2.5 and NO2 exposure was associated with chronic bronchitis and component symptoms. Results may have policy ramifications for PM10 regulation by providing evidence for respiratory health effects related to long-term PM10 to exposure.