This Day in History: 1966-11-22

Smog season begins for major cities. Smog episodes from coal smoke were typical in London for centuries, as this 1900 painting of Parliament by Claude Monet shows. But as London and other cities grew, especially heavy smogs were felt in 1952, 1953, 1962 and 1966, killing thousands. The severity of the incidents depended in part on variations in weather conditions, particularly thermal inversions that contain pollutants in enclosed regions. Other sources of smog proved even more dangerous over the years, such as air pollution from autos and petrochemicals.