Levels of ambient air pollution have been improving in Western countries with the setting of upper limits and better urban planning. However, that is not the case in many developing countries, particularly those with rapid industrialization.
Increased motor vehicle ownership and traffic congestion produce airborne particles of respirable size. These particles may be responsible for respiratory and cardiovascular effects and have been implicated in cancer pathogenesis.
The pathologic effects in the lung are mediated via inflammatory pathways and involve oxidative stress similar to cigarette smoking. These effects are seen in the peripheral airways where the smaller particle fractions are deposited and lead to airway remodelling. Definitive evidence of air pollution causing COPD is lacking and a different study design is required to link air pollution and COPD.
Contribution of air pollution to COPD and small airway dysfunction. Berend N. Respirology. 2015 Sep 27. doi: 10.1111/resp.12644 (full text).