London Smog of 1952

H. Dunnings


On December 5th, 1952 London, England was engulfed in a thick smog that sat motionless for four days. The smog was a mix of thick fog and smoky soot from the millions of coal powered stoves and local factories. At its most debilitating point the smog decreased visibility in the city to just one foot; bringing traffic and daily activities to a halt (Davis et al., 2002). Despite this, Londoners were so used to heavy smog that no one thought much of it that morning (Laskin, 2006). For them, it was just another smoggy day (Fig. 1).

Nelson's Column
Figure 1. Nelson's Column during London Smog of 1952 (Stobbs, 1952)

In the days that followed, residents could barely go outside without getting lost in their own neighborhoods. Still, the first ones to notice that this smog was taking a serious toll on the health of the population were the funeral homes; they were running out of coffins (Laskin, 2006). The weeks and months after followed suit as thousands of people experienced air pollution related illness and death. It wasn't until after the event that medical professionals realized the death toll had risen to about 4,000 above average (Fig. 2) that year (Wilkins, 1954). Additionally, it was estimated that another 8,000 people died prematurely as a result of the smog, bringing the total estimated death toll up to 12,000 (Davis et al., 2002). Among the dead were mostly people with pre existing conditions and the elderly.

Weekly Mortality Graph
Figure 2. Weekly mortality and SO2 concentrations for Greater London, 1952-1953 (Bell & Davis, 2001)


Several environmental factors contributed to the smog formation; the first were the meteorological conditions (Wilkins, 1954). The perfect conditions for a fog spell were underway in the Thames Valley that morning. The ground was cool after a long period of rain, the warm sun rose in the sky, and there were no incoming fronts to revive the wind that had been killed by the pre-exsisting high pressure system (Laskin, 2006). Typically the air closest to the ground is warmer, resulting in turbulence when that air rises. When the air rises, it also sweeps away some ground level pollutants and disperses them higher up in the atmosphere. The conditions were reversed that morning, resulting in a temperature inversion. This occurs when the warm and cool layers of air are inverted so the cool layer of air is closest to the ground. This creates a very stable environment in which water condenses easily to form fog. Fog gets agitated by the presence of wind; however, wind is limited in a stable atmosphere. The prolonged absence of wind allowed the fog to settle into the London basin for several days. Fog alone may cause some minor traffic delays, but the fog was also laced with soot and sulfur dioxide from the million or so coal powered stoves and local factory exhausts (Stone, 2002 and Wilkins, 1956). The cold December morning paired with the low visibility encouraged people to keep feeding their stoves with the standard cheap, low-grade coal that was available at the time (Laskin, 2006). This resulting smog was much thicker than “pure” fog and concentrated with particulate matter and other pollutants.

Effects on Environmental Policy

At first, it was hard to believe that people could drop dead simply from breathing dirty air. However, as it became apparent that the death toll was rising dramatically, the Ministry of Health took action. People no longer thought of the frequent london smog as romantic, and instead became increasingly concerned about their emissions. The Department of Scientific and Industrial Research started collecting data on concentrations of pollutants in the affected area. Air pollution data had previously been collected in Britain and the United States; however, this was the first time the data was sufficient enough to provide tangible results (Wilkins, 1954). This research brought attention to the relationship between air quality and health, and triggered the adoption of several environmental policies. In 1956, the British Clean Air Act was enacted which was the first legislation dealing exclusively with air pollution (Tracton, 2012). These policies were a major contributor in decreasing pollutant concentrations. As of 2002, PM10 concentrations were down to 30 μg/m3 as compared to the average 50 years ago of 300 μg/m3 (Davis et al., 2002).


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