Winter smog : The term "smog" was born in UK by the association of the two words "smoke" and "fog", caused by the high pollution generated by carbon for houshold heating. In the winter of 1952, about 4000 people died in London because of smog.
Nowadays, smog episodes caused by carbon are very lower and the SO2 emissions have a decreased trend. The sectors responsible of this kind of pollution are the energy production and the converting industry.
Smog episodes caused by carbon have still happened in the East-European, Asiatic and Latin-American metropolises.