It meant a combination of man-made SMOke and nature-made foG, but now it generally refers to photochemical smog trapped near the ground by a temperature inversion in colder climates. air pollution containing ozone and other reactive chemical compoundsformed by the action of sunlight on nitrogen oxides and hydrocarbons,especially those in automobile exhaust. It can inflame breathing passages, decreasing the lungs' working capacity, and causing shortness of breath, pain when inhaling deeply, wheezing, and coughing.

It can cause eye and nose irritation and it dries out the protective membranes of the nose and throat and interferes with the body's ability to fight infection, increasing susceptibility to illness. Hospital admissions and respiratory deaths often increase during periods when ozone levels are high.

Use photochemical smog in a sentence

A lot of people in crowded cities in Asia wear protective masks because there is to much Photochemical Smog in the air and they do not want to breathe it in. There was a lot of photochemical smog and it made peoples a bit uneasy because they thought it could be dangerous if it got out of hand.