Seventy years ago today The Great Smog of London was abating when a cold wind blew into London from the west and moved a deadly sulphuric cloud out to the North Sea.

Even though the cause of the disaster was gone, the lingering effects caused a death toll amounting to 12,000, injuring nearly a quarter of a million, sometimes permanently, and was instrumental in the mortality rate remaining higher than average throughout the following summer.

Under a perfect set of conditions, a combination of air pollution and fog combined into one of the worst ecological disasters of the 20th century.

After a century of experiencing this air pollution, Londoners were inured to this phenomenon. The smog was a result of the coal furnaces that began to appear in the 19th century as a result of the Industrial Revolution. The smoke and coal ash could be so thick at this time that it was known to change the colour of buildings and even turned 10 Downing Street’s bricks from yellow to black. People became so used to the colour that the building’s bricks were later painted in this familiar colour to maintain the look.

The smog that befell London had two root causes: man-made coal smoke and perfect weather conditions. For weeks before the event, the city had experienced an unusual cold snap and businesses, and residents alike burned even more coal to keep warm. Post-war coal was notoriously low-grade with a higher sulfur content (higher quality coal at the time was exported), which in turn added to the sulfur dioxide in the smoke that went up the chimneys and into the London air. In addition to the smoke released from homes and offices, the coal-burning furnaces of factories and major power plants in Battersea, Bankside, Lots Road and six others, contributed to even more pollution.

Londoners were pretty used to fog, but what rolled in on 5th December 1952 began to show that this was something radically different and very dangerous. The sulfur combined with the water particles in the smog gave it a yellowish black colour, leading the citizens to dub it a ‘pea-souper’, but no one on that first day could have known how deadly this fog would become. Trapped under the warm air, the smog became thicker to the point where people couldn’t see across the street, and some in East London reported that they couldn’t even see their own feet. Visibility at the time was done to 12 inches making driving impossible and simply crossing the street practically impossible. In less than a day, London was effectively shut down.

The real deadliness of the smog was not apparent at the beginning of the event. Some of the first casualties were birds who got lost in the smog and crashed into buildings. At Earl’s Court, eleven heifers choked to death at the Smithfield Show, forcing the remaining livestock owners to quickly fashion crude gas masks out of grain sacks soaked in whiskey. A performance of La Traviata at Saddler’s Wells Theatre had to be stopped after the first act because the audience could no longer see the stage, tickets were refunded. At Wigmore Hall similar conditions caused a concert to be abandoned as the stage began to be lost from view.

The smog accumulated to the level that it began to affect humans, and nearly everyone began to take it more seriously. Breathing in the air was equivalent to inhaling acid rain, and those most susceptible were children, the elderly, and persons who already had difficulty breathing. It wasn’t long before the city’s hospitals were inundated by the affected. The death rate in London’s East End multiplied by nine, while overall deaths from bronchitis and pneumonia increased by a factor of seven. Even so, the serious health problems presented by the smog were not apparent to the average Londoner until florists began to experience a lack of blooms and undertakers started running out of coffins.

Later questions were asked in Parliament, and after several Government inquiries The Clean Air Act 1956 was enacted which had multiple measures to reduce air pollution, it brought in the introduction of ‘smoke control areas’ in towns and cities in which only smokeless fuels could be burned. Shifting domestic sources of heat towards cleaner coals, electricity, and gas reduces the amount of smoke pollution and helps to remove sulphur dioxide from household fires.

It would ultimately be the start of banning the use of carbon-based fuels to provide for London’s energy needs.