On this day in 1952, a thick and dense smog hovered over London, England. It began on December 5th, and persisted for 4 days.
During the day on December 5th, the fog was not especially dense and generally possessed a dry, smoky character. When nightfall came, however, the fog thickened. Visibility dropped to a few meters. The following day, the sun was too low in the sky to burn the fog away. That night and on the Sunday and Monday nights following, the fog again thickened. In many parts of London, it was impossible at night for pedestrians to find their way, even in familiar districts. In The Isle of Dogs area, the fog there was so thick people could not see their feet.
All transportation in the region was halted, but not before the smog caused several rail accidents, including a collision between two trains near London Bridge. The worst effect of the smog, however, was the respiratory distress it caused in humans and animals, including difficulty breathing and the vomiting of phlegm. The smoke-like pollution was so toxic it was even reported to have choked cows to death in the fields. One of the first noted victims was a prize cow that suffocated on December 5th.
The official death toll was difficult to calculate, but most estimates place the death toll at 4,000, with some estimating that the smog killed as many as 8,000 people.