1. Increase risk of infection. Air pollutant can irritate the respiratory airway and directly destroy the cilia. Cilia is hair organelle in respiratory airways that will catch dust or bacteria then move it out of the airway.
2. Damaging lung. Some pollutant like asbestos also deposited in the lung, inducing inflammation and destroy it directly. Many pollutants also carcinogenic, meaning that it can cause lung cancer.
3. Damaging other organs. Other pollutants can disturb non-respiratory. Cyanide can bind into the blood and decrease oxygen delivery.