From 5 to 9 December 1952, thick, filthy, toxic smog, a combination of industrial pollution, domestic coal fire burning and unusual weather conditions blanketed the London area.
Visibility was reduced to less than a metre in places, bringing the city to a virtual standstill. An estimated 12,000 Londoners died, including babies, citizens with respiratory problems and elderly people. More than 100,000 people became ill, with many hospitalised.
This catastrophic event, the worst pollution incident ever in Britain, prompted the Clean Air Act of 1956, a watershed moment in the history of environmentalism.
Here, we look at what led to the Great Smog and what happened.
The rise of industry
19th century London, like much of Britain, saw rapid industrialisation following the Industrial Revolution (1760 to 1840). The traditional agrarian and craft skills economy had been largely replaced by machine manufacturing, with factories and mills driven by coal-powered steam engines.
As increasing numbers of people moved from rural areas to the city to search for work, there was a huge growth in London’s population over the 19th century, from one million in 1801 to around six million.
London’s ‘pea soupers’, dense yellow fog, became a common feature of life, (continuing into the first half of the 20th century) as emissions and gases from factory chimneys increased, coupled with families burning coal to warm their homes and to provide fuel for cooking.
How did the Great Smog form?
The winter of 1952 was freezing. Households burnt enormous amounts of coal to keep warm. Smoke poured out of hundreds of thousands of chimneys. This cheap low-grade coal was more poisonously sulphurous than the hard high-grade version that the government exported to maximise revenues and pay off war debts following the Second World War (1939 to 1945).
Factories and power stations were also continually belching out smoke. Pollution from steam locomotives, powered by coal, and exhaust from vehicles added to the toxic mix.
But it was a rare weather event that triggered the deadly smog:
Usually, smoke and pollution would rise up into the atmosphere and disperse naturally, but an anti-cyclone (high pressure) had stalled over a windless London, allowing a layer of fog up to 200 metres deep to form over the city at ground level, trapping the pollutants, included the highly dangerous gas, sulphur dioxide. This toxic mix resulted in a thick, stinking smog.
What were the effects of the Great Smog?
The smog was so dense in some places that people could barely see their own feet. Their clothes and faces were blackened with soot. There was often a smell of rotten eggs. People made improvised face coverings. The number of street robberies rose.
Transport was severely affected. Police officers guided traffic with flares. Bus conductors, using flashlights or flares, walked in front of their buses to show the way. There were many traffic accidents.
Train drivers, inching along the tracks and unable to see signals, were alerted to them by a loud bang as the train wheels ran over a small explosive charge laid for the purpose of railway lines. Flights were cancelled or diverted. Boat traffic on the River Thames came to a halt. Only the underground was unaffected. Thousands of people queued for tickets to get to their destinations.
Schools and many workplaces were closed. Sporting fixtures were called off. The smog seeped into homes, and into the auditoriums of theatres and cinemas, obscuring the stage and screen.
A number of previously healthy young cattle were slaughtered at the Smithfield Show at Earl’s Court to prevent them from suffocating to death after they displayed acute respiratory symptoms, with one animal having already died due to the smog.
On 9 December, five days after the smog began, the weather changed and the smog lifted. A brisk wind got up, clearing the air and revealing greasy black-streaked streets, buildings and trees.
The Great Smog stretched 40 miles (64 kilometres) across the London area, according to contemporary headlines.
In its immediate aftermath, it was estimated that the number of people who had lost their lives was around 4,000, but a scientific re-assessment in 2004 suggested that as many as 12,000 Londoners may have died. The further 8,000 having died over the course of the following year (1953), most from respiratory tract infections caused by the smog.
The tragic event of 1952 was unignorable and the government passed the Clean Air Acts of 1956 and 1968. These restricted the burning of coal in urban areas, including factories which had to convert to smoke-free fuels. Local councils were given powers to set up smoke-free zones. Homeowners were offered grants to convert from coal to central heating.
However, the move away from coal was slow. Deadly fogs still occurred, including one in 1962 which killed around 750 Londoners, but nothing on the scale of the Great Smog of 1952.
Pollution legislation and the widespread use of central heating has ensured that such an extreme event has been consigned to history.
But London’s air pollution has not gone away. With the huge growth in the number of vehicles, the chemical mix is now more insidious and invisible. In 2003, the Congestion Charge Zone in Central London was introduced. Most motorists have to pay each time they enter the Zone, this financial deterrent helping reduce traffic flow and thereby pollution.
Written by Nicky Hughes.