pea soup fog

For years London was synonymous with smog, the word coined at the turn of the 20th century to describe the city's characteristic blend of fog and smoke. The capital's "pea-soupers" were caused by suspended pollution of smoke and sulphur dioxide from coal fires... That problem was alleviated by parliamentary legislation (the Clean Air Acts of 1956 and 1968) outlawing the burning of coal.

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