Great Smog of London (1952): The Deadly Fog and the Clean Air Act

The Great Smog of London was a severe air pollution event that covered the British capital from 5 to 9 December 1952. A mixture of fog and coal smoke, trapped by cold, windless weather, caused thousands of deaths and sickened many more. It remains one of the deadliest environmental disasters in European history and the turning point that led to the Clean Air Act of 1956.

Background: a city that ran on coal

In the early 1950s London was still a city heated by coal. Most of its roughly 8 million inhabitants warmed their homes with open coal fires, and coal-burning power stations such as Battersea, Bankside and Fulham stood inside the city. Factories, steam trains and a growing number of diesel buses added to the smoke.

Fog was nothing new. Londoners had complained about smoky “pea souper” fogs for centuries, and the problem had been worse in the Victorian era, when it inspired writers and painters. In the years after the Second World War, however, Britain was short of money and exported much of its best coal. Households were often left with cheaper, lower-grade coal that produced more smoke and sulphur.

Earlier warnings had been largely ignored. Smoke abatement campaigners had argued for decades that coal smoke harmed health, but there was little political will to change the way millions of people heated their homes.

What happened in December 1952

On Thursday 4 December 1952 an anticyclone, a large area of high pressure, settled over south-east England. Winds dropped almost to nothing. On the night of 4–5 December the ground cooled quickly and a layer of fog formed under a lid of warmer air above it. This “temperature inversion” stopped the smoke from rising and drifting away.

Because the weather was cold, Londoners burned more coal than usual. Day by day the fog absorbed more soot, tar particles and sulphur dioxide and turned yellow-black. The Met Office later estimated that during each day of the smog around 1,000 tonnes of smoke particles were released into the London air, along with hundreds of tonnes of sulphur dioxide, much of which became sulphuric acid in the fog droplets.

Visibility in parts of central London fell to a few metres, and in some places people could not see their own feet. Buses crawled behind men walking ahead with flares or torches, and ambulances largely stopped running, so many patients had to make their own way to hospital. Flights were grounded and river traffic halted. The smog also seeped indoors: a performance of La Traviata at Sadler’s Wells Theatre was abandoned because the audience could no longer see the stage, and cinemas closed when the screens became invisible.

At the Smithfield Show, an agricultural exhibition at Earls Court, prize cattle suffered from breathing difficulties and some died or had to be slaughtered. Their fate was reported in newspapers before the full scale of human deaths was understood.

On Tuesday 9 December the wind returned and the smog cleared.

The human toll

Few people realised during the smog itself how many were dying. The first clear sign came from undertakers and florists, who reported running short of coffins and flowers. When the weekly death figures were compiled, they showed that deaths in Greater London had risen to several times the normal level, mainly from bronchitis, pneumonia and heart failure.

The very young, the elderly and people with existing lung or heart disease were most at risk. A Ministry of Health report published in 1954 put the number of extra deaths in the first weeks at about 4,000. Death rates stayed unusually high into early 1953, but the government attributed many of these later deaths to an influenza outbreak.

Modern researchers have challenged that explanation. In 2001 Michelle Bell and Devra Davis argued that influenza could account for only a small part of the excess and that around 12,000 deaths between December 1952 and February 1953 could be linked to the smog. Historians now usually quote a range of about 4,000 to 12,000 deaths, depending on the period counted.

The political response

The Conservative government of Winston Churchill was at first reluctant to act. Harold Macmillan, then Minister of Housing and Local Government, and Iain Macleod, the Minister of Health, faced questions in Parliament, but ministers feared the cost of controlling household smoke when coal was still rationed and housing was in short supply.

Under public pressure, the government set up a committee in 1953 chaired by the engineer and businessman Sir Hugh Beaver. Its report, published in 1954, concluded that air pollution on this scale was a serious danger to health and recommended controlling smoke from both industry and homes. The Conservative MP Gerald Nabarro also pushed the issue with a private member’s bill, which helped persuade the government to bring forward its own legislation.

The Clean Air Act 1956

The Clean Air Act received royal assent on 5 July 1956. Its main provisions were:

• local authorities could declare smoke control areas, in which only smokeless fuels such as coke, gas or electricity could be used for heating;
• government grants helped households pay to convert or replace their open grates;
• industrial chimneys had to be tall enough to disperse smoke, and the emission of “dark smoke” from chimneys was restricted;
• new power stations were increasingly built away from city centres.

The act worked slowly, because councils introduced smoke control areas gradually. A further smog in December 1962 killed several hundred Londoners, and a second Clean Air Act followed in 1968. By the 1970s the switch to gas central heating, electricity and North Sea gas had largely ended London’s coal-smoke fogs.

By the numbers

Legacy

The Great Smog changed how governments thought about pollution. It showed that ordinary domestic activity, not only heavy industry, could cause a public health catastrophe, and it gave Britain one of the first comprehensive clean air laws in the world. It came almost a century after the Great Stink of 1858, when the smell of the polluted Thames pushed Parliament to build London’s sewers.

The disaster also influenced research. Studies of London’s smog helped establish the link between fine particles in the air and deaths from heart and lung disease, a link that underpins air quality standards today. In the United States, rising concern over urban smog contributed to the federal clean air laws of the 1960s and to the creation of the Environmental Protection Agency in 1970.

In 2016 an international team of scientists reported that chemical reactions within the fog droplets, involving sulphur dioxide and nitrogen dioxide, help explain how so much sulphuric acid formed so quickly. They noted that similar chemistry occurs in severe haze episodes in some Chinese cities today, which is one reason the 1952 smog is still studied. The episode also returned to public attention when it was dramatised in the television series The Crown in 2016.

Timeline

• 1952, 4 December: An anticyclone settles over London; winds drop and the air turns cold.
• 1952, 5 December: Fog forms under a temperature inversion and begins to fill with coal smoke.
• 1952, 6–8 December: Visibility falls to a few metres; transport, theatres and the Smithfield Show are disrupted; deaths rise sharply.
• 1952, 9 December: A change in the weather brings wind and the smog disperses.
• 1953: The government appoints the Beaver Committee on air pollution.
• 1954: The Beaver Committee reports; a Ministry of Health report puts the excess deaths at about 4,000.
• 1956, 5 July: The Clean Air Act receives royal assent.
• 1962, December: Another London smog kills several hundred people.
• 1968: A second Clean Air Act extends the controls.

Why it matters

The Great Smog showed that the air of a modern city could kill on a massive scale within days. It ended a long tolerance of coal smoke in Britain, produced landmark legislation and helped lay the foundations of modern air pollution science and regulation.