The authors conducted a cross-sectional study among residents of Delhi to determine the role of ambient air pollution in chronic respiratory morbidity in Delhi. The authors selected a random, stratified sample (N = 4,171) of permanent residents who were 18+ y of age and who lived near 1 of the 9 permanent air quality monitoring stations in the city. Air-quality data for the past 10 y were obtained; data were based on the differences in total suspended particulates, and the study areas were categorized into lower- and higher-pollution zones.

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