Why do some cities have worse SMOG problems than others?
The frequency and severity of smog depends upon the size of a city, its population and vehicle density and the kind of industry it supports. Smog is not just a city problem; it flows into rural areas as well. Since ozone, NOx and VOC can be transported by air over long distances, the frequency and severity of smog in a particular area can be affected by smog levels in areas several hundred kilometres away. Climate and topography also affect smog levels. Although rain can clean the air of the pollutants that cause smog, this may result in acidic rain water. Wind, too, can blow smog away, but if cities are surrounded by hills or mountains, air flow patterns are reduced, and smog levels increase.
