SMOG

[noun] - a type of air pollution in some large cities that is caused either by smoke from burning wood and coal mixing with water in the air to produce a type of dirty fog or by chemicals produced by road vehicles reacting with bright light from the sunSmog is a major problem in Los Angeles. [U]Such high levels of smog would not normally be expected in a coastal city, where sea breezes should help to disperse it. [U]As we flew into the airport, we could see a murky yellow smog hovering over the city. [C]