We’ve all heard about smog, but did you know it varies in different cities around the world?
Not all smog is created equal. Just like any type of soup, it’s all in what you put in it. Smog is a low-level 
atmospheric mixture of several different kinds of air pollution. In some areas, such as those near coal-fired power plants, the main constituents of smog are the byproducts of fossil-fuel burning such as sulfur dioxide, ground level ozone and carbon monoxide. Massive smog events can also be caused by residential coal burning, as in the case of the “Great London Smog of 1952″ that killed thousands in a few weeks.
Cities that are near active volcanoes (such as Mt. Etna in Sicily and many others) are especially likely to suffer from infrequent but very traumatic smog events. In this case, though entirely natural, many of the chemical components of this “vog” are the same as what might be seen with petrochemical smog. Sulfur dioxide and very harmful, tiny, caustic particles are also a concern.
Smog in the air is bad no matter what.