The Great Smog Of London Which Killed 12,000 People In 1952

The Great London Smog of 1952 severely affected a large area of ​​the UK capital. A dense and toxic fog lasted a full five days and is still regarded as one of the worst cases of air pollution in history.

The Great Smog Of London Which Killed 12,000 People In 1952

On 5 December 1952 , an extremely dense blanket of fog  fell over the city of London. Hardly anyone seemed to pay much attention to it, and the day went by not too differently from the previous ones. Soon, however, citizens began to notice that the fog was extremely thick and dense , visibility reduced to a minimum and, above all, the cases of respiratory crises and related cardiac arrests began to significantly increase.

Over the next five days , a low curtain of mist and smoke fell over London and the city became the scene of accidents, crime and chaos. Various factors caused the disaster that cost the lives of 12,000 people: first of all, the great atmospheric pollution that had been affecting the capital for some time, and which depended above all on the excessive use of coal as an industrial and urban fuel . In addition, an anticyclonic phase , therefore of high pressure, did not allow the harmful substances present in the air to disperse and this congested the city and caused the disaster that today, 71 years later, we remember with the name of the "great smog of London ”.

Where does the word smog come from and when was it born

Before going into detail about the substances that polluted the air to the point of making it unbreathable, we wanted to tell you that the term smog was coined by a doctor to describe the particular atmospheric condition that affected the British capital at that time and, more generally, the big cities. In 1905, Dr. Henry Antoine Des Voeux, on the occasion of the Public Health Congress in London , made known to his colleagues a new term, from the union of the words “ smoke ” (from the English, “smoke”) and “ fog ” (from 'English, "fog"). The set of words led to the coining of smog, which has since been the name used to indicate the mix of fog and fumes produced by industries, vehicles and human activities, which forms mainly in urban areas and in the presence of high humidity.

The characteristics of London's great smog

The great smog of London has been studied for a long time, over the years, and today it is remembered as one of the worst cases of air pollution in the world. The repercussions that those five days of smog had on public health continued to manifest themselves in the following months and even years.

Chemically, the Great London Smog of 1952 was a concentration of pollutants , released into the atmosphere and held over the city by an anticyclone . If you're wondering how this works, you have to imagine an area of ​​high pressure, which pushes the air down to the earth's surface, creating a sort of "cap" of warm air. Following the thermal inversion that is generated between the warm temperature of the air and the colder one of the ground, fog and haze are naturally created . To this were added the polluting substances (retained by the "roof" of hot air), and given by the use of coal,which in those years was burned both in homes and in factories.

We must remember that London was an industrial city and along the Thames , the river that crosses the center of the metropolis, there were once factories and power stations that used coal. Thanks to the rigid temperatures of the end of Autumn, even the citizens strongly fueled their home heating systems. A chain reaction that caused the stalemate of huge quantities of toxic substances. Specifically, it is estimated that 1000 tons of smoke , 2000 tons of carbon dioxide and 370 tons of sulfur dioxide were released into the environment each day (Laskin, 2006).
The following compounds mainly polluted the air of London in that historical period:


The word "smoke" means the presence of very small solid particles dispersed in a gas. The particles can be of different nature, from carbon atoms to residual compounds of incomplete combustion such as paper, plastics, etc. The range of values ​​considered normal , for London in 1952, predicted an amount of smoke between 0.44 and 0.12 milligrams per cubic meter of air (mg/m ³) . In the days of the great smog, however, the concentrations increased dramatically, especially in the first three days, reaching the maximum value of 4.46 mg/m ³ in the very central district of Lambeth, near the County Hall building , once the Town Hall.

Sulfur dioxide

Sulfur dioxide ( SO₂ ) is composed of a sulfur atom to which two oxygen atoms are bonded. Present in the air of London, the amounts considered normal were between 0.23 and 0.07 parts per million (ppm). In the days of the great smog (in particular, from 6 to 8 December 1952) the maximum value of 1.34 ppm was recorded , near County Hall, in the centre. High concentrations of sulfur dioxide occurred mainly within a radius of about three kilometers, between Westminster and Charing Cross. It should be remembered that in contact with water (H ₂ O), sulfur dioxide forms sulfuric acid (H ₂SO₄ ), another of the secondary compounds that increased air pollution .

Carbon monoxide and carbon dioxide

Although the increase in carbon monoxide and carbon dioxide in the air was not immediately tracked, based on the study released by the Journal of The Royal Sanitary Institute in 1954, we do know that, compared to normal concentrations, listed at around 34 ppm, in days of the great smog there was an increase in carbon monoxide of about 0.03%. Carbon dioxide followed a very similar pattern and increases are estimated to range between 0.2 and 0.5%.

The effects of London's great smog

Beyond the chaos generated by the smog , so thick and dense as to not allow the normal circulation of vehicles, London was at the center of all kinds of inconveniences. Departing planes were blocked and the trajectory of arriving ones diverted to airports in other cities. There were dozens of accidents , delays in emergency vehicles , crowded hospitals and even a significant increase in robberies and crime events, which transformed the city into a veritable theater of horror. Above all, however, exposure to pollutants was devastating to healthof citizens. The youngest and the elderly began to feel bad, and all the people with pre-existing chronic pathologies. Cough, asthma, pneumonia and cardiac arrest resulted in 4,000 deaths in the first few days alone. It is estimated, however, that the total victims caused by the great smog of London were about 12,000. [Polyvka, 2018]

The Clean Air Act  of December 9, 1952

On Tuesday, December 9, 1952, after horrible days and desperation, a low pressure area arrived over the city, finally bringing wind and rain. London breathed again. As the weeks went by, the catastrophic dimensions of the event became more and more evident and a committee was set up , led by Sir Hugh Beaver, whose objective was to determine the sources of pollution and draw up a series of recommendations for industries and citizens . These documents formed the basis of the Clean Air Act , a law that received royal assent in 1956 and which allowed authorities to control pollutant emissions and establish smoke-free zones.
Fun fact: in the aftermath of the Clean Air Act,   death rates for London men dropped by about half. [The Health Foundation]

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