Smokeless zones are a British response to urban air pollution, a part of a city where the combustion of a smoke-producing fuel (notably coal) is prohibited. Human health was becoming seriously endangered by the proliferation of dirty fuels, with respiratory ailments becoming widespread.
As far back as the 13th century the use of sea coal, which was used in large quantities by the lime industry, was prohibited in London. Both increasing population and declines in fuel wood supply led to increased use of coal, and meant that by the late 19th century Public Health Acts had various clauses that attempted to reduce smoke.
London's population-induced smoke problems were exacerbated by thick fogs. The fog mixed with the smoke to create a deadly smog (note that this is different from the photochemical car emission smog of Los Angeles). In December 1952, a four day smog during a cold snap (i.e., more coal was being burnt) led to between 4,000 and 4,700 deaths over and above the expected number. Most people who died were already suffering from some sort of respiratory ailment such as bronchitis.
The first smokeless zones were created under the city of London (Various Powers) Act of 1946. The smokeless zones not only reduced the amount of smoke, but also reduced sulphur dioxide emissions. People switched to electricity, gas, or low sulphur oils for heating. By 1987, 90% of London was covered by smokeless zones.
Not surprisingly, the number and intensity of deadly smogs has declined with the drop in coal's importance as a fuel.
The Great Smog of 1952 led to the Clean Air Act (1956), which gave the power to create smokeless zones to other local governments.
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