Heavily polluted air (4)
I believe the answer is:
smog
(Other definitions for smog that I've seen before include "Pollutant fog" , "Thick polluted mist" , "Pollution haze/fog" , "Smoky haze" , "Visible air pollution" .)
I believe the answer is:
smog
(Other definitions for smog that I've seen before include "Pollutant fog" , "Thick polluted mist" , "Pollution haze/fog" , "Smoky haze" , "Visible air pollution" .)