When a thick fog engulfed London from December 5-9, 1952, it mixed with black smoke emitted from homes and factories to create a deadly smog. This smog killed about 12,000 people and shocked the world into starting the environmental movement.

Smoke + Fog = Smog

When a severe cold spell hit London in early December 1952, Londoners did what they usually did in such a situation -- they burned more coal to heat up their homes. Then, on December 5, 1952, a layer of dense fog engulfed the city and stayed for five days.

An inversion prevented the smoke from the coal burning in London's homes, plus London's usual factory emissions, from escaping into the atmosphere. The fog and smoke combined into a rolling, thick layer of smog.

London Shuts Down

Londoners, used to living in a city known for its pea-soup fogs, were not shocked to find themselves surrounded by such thick smog. Yet, although the dense smog did not instill panic, it nearly shut down the city from December 5-9, 1952.

Visibility across London became extremely poor. In some places, visibility had gone down to 1 foot, meaning that you wouldn't be able to see your own feet when looking down nor your own hands if they were held out in front of you.

Transportation across the city came to a standstill, and many people didn't venture outside for fear of getting lost in their own neighborhoods. At least one theater was closed down because the smog had seeped inside and the audience could no longer see the stage.

The Smog Was Deadly

It wasn't until after the fog lifted on December 9 that the deadliness of the smog was discovered. During the five days in which the smog had covered London, over 4,000 more people had died than usual for that time of year. There were also reports that a number of cattle had died from the toxic smog.

In the following weeks, about 8,000 more died from exposure to what has become known as the Great Smog of 1952. It is also sometimes called "the Big Smoke." Most of those killed by the Great Smog were people who had pre-existing respiratory problems and the elderly.

The death toll of the Great Smog of 1952 was shocking. Pollution, which many had thought was just a part of city life, had killed 12,000 people. It was time for a change.

Taking Action

The black smoke had caused the most damage. Thus, in 1956 and 1968 the British Parliament passed two clean air acts, beginning the process of eliminating the burning of coal in people's homes and in factories. The 1956 Clean Air Act established smokeless zones, where smokeless fuel had to be burned. This law dramatically improved air quality in British cities. The 1968 Clean Air Act focused on the use of tall chimneys by industry, which dispersed the polluted air more effectively.