While urban air pollution is a contributing factor in exacerbations , its overall role as a cause of COPD is unclear .
People who live in large cities have a higher rate of COPD compared to people who live in rural areas .
While urban air pollution is a contributing factor in exacerbations , COPD 's overall role as a cause COPD COPD is unclear .
People who live in large cities have a higher rate of COPD compared to people who live in rural areas .