Smog is a term used to describe a combination of smoke and fog. Very specific weather conditions mixed with air pollution can form a deadly cocktail. The Industrial Revolution, with its factories and incinerators, kick-started these deadly incidents, but wildfires and other pollutants have also played a role in many of these smog events.
In this gallery, we look back in history and bring you the deadliest smogs to date. Click on to discover them all.