Hi. Chalazion, stye, acute dacrocystitis , insect bite could be the causes for this. Pollution unlikely to cause single eye swelling.Wash hands thoroughly to prevent any bacteria from transferring to the already infected eye.  Take a clean washcloth and fold it into quarters. Use a small bowl and fill with warm (preferably filtered) tap water Take the washcloth and submerge in the water, Apply the hot washcloth to the eye area with your eye closed in 5 minute intervals. This may relieve some pain and pressure, and help the body release the infection. Consult opthalmologist.