London's Kiling Fog

To get a better idea of what is smog and the Great Smog incident, let's firstly watch a video by SciShow:

In previous posts, I mentioned the Meuse Valley air pollution incident that caused the death of over 60 people. This incident raised an alarm in the public and scientific community about how devastating air pollution can be. However, this did not bring the end of air pollution. On the contrary, it was only a beginning of series of tragedies caused by air pollution. In December 1952, a thick blanket of toxic smog shrouded London, killing an estimated 8,000 to 12,000 people (Klein, 2012).

Similar to the Meuse Valley incident, a high-pressure weather system with warm air above cold air prevented London's sulfurous coal smoke from rising. Moreover, there was, unfortunately, no wind to disperse the soot-laden smog. For five days, the Great Smog that was 30-mile-wide paralyzed London and crippled all ground transportation due to the poor visibility. 

fig.1 Image of a conductor in the Great Smog of London

Health Impact of the Great Smog

Same as most of the air pollution incidents, the elder, the young, and those with respiratory problems are the most affected by the Great Smog in 1952. Death from bronchitis and pneumonia increased more than sevenfold, and the death rate in London's east end increased by about nine times (Klein, 2012). According to a BBC report, 4,075 more people had died than would have been expected to under normal conditions. The death rate remained high above normal level until the summer of 1953. The majority in the scientific community now estimate the Great Smog claimed at least 8, 000 lives, even probably as many as 12,000.

fig.2 Deaths, sulphur dioxide concentration, and smoke in December 1952

The Great Smog's  impact on health is even long-term. according to an article by Bharadwa el al. (2016), exposure to the Great Smog in the first year of life increases the likelihood of childhood asthma by 19.87 percentage points. There is also suggestive evidence showing that early-life exposure led to a 9.53% higher likelihood of adult asthma, and exposure in utero led to a 7.91% higher likelihood of childhood asthma.


After the Great Smog

The incident in 1952 directly pushed British government to introduce the Clean Air Act in 1956. The act aimed to control domestic sources of smoke pollution by introducing smokeless zones, where smokeless fuels had to be burnt. Air quality in cities was dramatically improved through following methods:

• setting smoke control area to reduce domestic emissions;
• increase in electric and gas usage and the decline in solid fuel consumption;
• usage of cleaner coals with lower sulphur content;
• using tall chimney stacks on power stations;
• relocating power stations to rural areas;
• the decrease in heavy industry.

Next week, I'm going to post more about the second important pollutant (as sulphur dioxide was the major pollutant, and I've written about it in last two posts) in this incident, the black carbon particles. I will discuss how black carbon affects human health, and its contribution to modern environmental problems and climate change.