Answer-Smog is a combination of –

Smogisatypeofairpollutionthe word smog was coined in the early 20th century as a portmanteau of the words smoke andfogtorefertosmokyfog.Thewordwasthen intendedtorefertowhat was sometimes known as pea soup fog, a familiar and serious problem inLondonfromthe19thcenturytothemid20th century. This kind of smog is caused by the burning of large amounts of coal within a city thissmogcontainssootparticulatesfromsmoke, sulfur dioxide and other components.