The worst air pollution event in the history of the United Kingdom, and significant in its effect on regulation of air quality. Due to burning of cheap, suplphur heavy coal, cold weather and windless conditions the smog created by industry and heating would not disperse. The smog even seeped indoors, canceling events such as concerts and movie showings due to visibility.
Heavy smog due to coal heating, visbility less than a metre
Air pollution caused 12,000 fatalities