Air pollution common in big cities (4)
I believe the answer is:
smog
(Other definitions for smog that I've seen before include "Smokey fog" , "Pollution fog" , "Polluted haze" , "Pollutant fog" , "Fog polluted by smoke" .)
I believe the answer is:
smog
(Other definitions for smog that I've seen before include "Smokey fog" , "Pollution fog" , "Polluted haze" , "Pollutant fog" , "Fog polluted by smoke" .)