The deadliest smogs in history
1948: Donora, Pennsylvania: Donora had two big industrial plants, namely the Donora Zinc Works.
1948: Donora, Pennsylvania: An uncommon weather event trapped air pollution, and the smog.
1948: Donora, Pennsylvania: It's estimated that 43% of the local population suffered long-term health effects following the smog.
2010: Moscow, Russia: In the summer of 2010, the Russian capital endured one of the worst heat waves in the country's history.
2010: Moscow, Russia: As a result, Moscow's daily mortality rate skyrocketed from around 370 people to 700.
2010: Moscow, Russia: It is estimated that around 104,000 people fled Moscow during this period.
19th century: London, England: Most people will associate smog with London.
19th century: London, England: Records of smog events in the capital go as far back as 1813.
19th century: London, England: The overall death rate is unknown, but one event in particular, in 1873.
1930: Meuse Valley, Belgium: Before becoming the idyllic European destination that it is today, in 1930.