Association of outdoor air pollution with chronic respiratory morbidity in an industrial town in northern India

A cross-sectional study was performed in one industrial (study) and one non-industrial (reference) town in Punjab State, northern India. Ambient air quality samples were collected and analyzed each week for 2 yr. Subjects were 3,603 individuals >15 yr old who were interviewed and whose lung functions were measured spirometrically. Their biomarkers were categorized in terms of obstructive or restrictive defects. Levels of total suspended particulates, nitrogen oxides, sulfur oxides, carbon monoxide, and ozone were significantly higher in the study town than in the reference town. The prevalence of chronic respiratory symptoms (cough, phlegm, breathlessness, or wheezing) was 27.9 and 20.3% in the study and reference towns, respectively (p < 0.05). That of obstructive ventilatory defect was 24.9 and 11.8% (p < 0.05), respectively. Logistic regression analysis showed that residence in the study town was independently associated with chronic respiratory symptoms (odds ratio [OR] = 1.5; 95% confidence interval [CI] = 1.2, 1.8; p < 0.001) and spirometric ventilatory defect (OR = 2.4; 95% CI = 2.0, 2.9; p < 0.001) after controlling for other demographic effects.