The Great Smog of 1952 or Big Smoke was a severe air-pollution event that affected London during December 1952. A period of cold weather, combined with an anticyclone and windless conditions, collected airborne pollutants mostly from the use of coal to form a thick layer of smog over the city. It lasted from Friday 5 December to Tuesday 9 December 1952, and then dispersed quickly after a change of weather.
Although it caused major disruption due to the effect on visibility, and even penetrated indoor areas, it was not thought to be a significant event at the time, with London having experienced many smog events in the past, so-called "pea soupers". Government medical reports in the following weeks estimated that up until 8 December 4,000 people had died prematurely and 100,000 more were made ill because of the smog's effects on the human respiratory tract. More recent research suggests that the total number of fatalities was considerably greater, at about 12,000.
It is known to be the worst air-pollution event in the history of the United Kingdom, and the most significant in terms of its effect on environmental research, government regulation, and public awareness of the relationship between air quality and health. It led to several changes in practices and regulations, including the Clean Air Act 1956.
There was no panic, as London was renowned for its fog. In the weeks that ensued, however, statistics compiled by medical services found that the fog had killed 4,000 people. Most of the victims were very young or elderly, or had pre-existing respiratory problems. In February 1953, Lieutenant-Colonel Lipton suggested in the House of Commons that the fog had caused 6,000 deaths and that 25,000 more people had claimed sickness benefits in London during that period.
The cold weather preceding and during the smog meant that Londoners were burning more coal than usual to keep warm. Post-war domestic coal tended to be of a relatively low-grade, sulphurous variety (economic necessity meant that better-quality "hard" coals tended to be exported), which increased the amount of sulphur dioxide in the smoke. There were also numerous coal-fired power stations in the Greater London area, including Fulham, Battersea, Bankside, and Kingston upon Thames, all of which added to the pollution. According to the UK MetOffice, the following pollutants were emitted each day during the foggy period: 1,000 tonnes of smoke particles, 2,000 tonnes of carbon dioxide, 140 tonnes of hydrochloric acid, 14 tonnes of fluorine compounds and 370 tonnes of sulphur dioxide.
On 4 December 1952, an anticyclone settled over a windless London, causing a temperature inversion with cold, stagnant air trapped under a layer (or "lid") of warm air. The resultant fog, mixed with chimney smoke, particulates such as those from vehicle exhausts, and other pollutants such as sulphur dioxide, formed a persistent smog, which blanketed the capital the following day. The presence of tarry particles of soot gave the smog its yellow-black colour, hence the nickname "peasouper".The absence of significant wind prevented its dispersal and allowed an unprecedented accumulation of pollutants.
Research suggests that additional pollution-prevention systems fitted at Battersea may have worsened the air quality, reducing the output of soot at the cost of increased sulphur dioxide, though this is not certain. Additionally, there were pollution and smoke from vehicle exhaust — particularly from steam locomotives and diesel-fuelled buses, which had replaced the recently abandoned electric tram system — and from other industrial and commercial sources.Prevailing winds had also blown heavily polluted air across the English Channel from industrial areas of Continental Europe.
Most of the deaths were caused by respiratory tract infections from hypoxia and as a result of mechanical obstruction of the air passages by pus arising from lung infections caused by the smog. The lung infections were mainly bronchopneumonia or acute purulent bronchitis superimposed upon chronic bronchitis.
More recent research suggests that the number of fatalities was considerably greater, at about 12,000.
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