London had burned coal for centuries, and its “pea-souper” fogs were a music-hall joke, a Dickens set-piece, almost a civic institution. December 1952 supplied the reminder that the joke was made of sulphur.
On 5 December a high-pressure system parked over the city and the wind died. A temperature inversion — warm air capping cold — sealed the basin of the Thames valley like a lid. Beneath it, a cold snap had every grate in the city burning hard: postwar households burned low-grade, high-sulphur coal (the good stuff was exported), joined by coal-fired power stations, diesel buses that had just replaced the electric trams, and steam locomotives.
Five days under the lid
The smog thickened until visibility fell to a few metres, in places to less than an arm’s length. Buses crawled behind conductors walking with flares; river and air traffic stopped; ambulances gave up, leaving the sick to make their own way to hospital through streets they could not see across. The smog seeped indoors: cinemas closed because audiences could not see the screen, and the opera at Sadler’s Wells was abandoned mid-performance. At the Smithfield show, prize cattle collapsed and died with blackened lungs. Skin and window-sills wore an oily black film; those who walked outside blew black soot from their noses.
The air itself was measurably poisonous: sulphur dioxide and smoke concentrations many times any modern legal limit, the droplets converting to dilute sulphuric acid in the fog and in bronchial passages. The elderly, infants, and anyone with weak lungs began to die in numbers the city did not immediately grasp — there was no dramatic scene, just full mortuaries. Undertakers ran short of coffins, florists of wreaths.
Counting the dead
When the wind returned on 9 December and the fog rolled out to the North Sea, the registrar’s figures showed roughly 4,000 excess deaths in the smog week — a toll on the scale of a cholera epidemic, in a modern capital, from the air. Deaths ran above normal for months; later epidemiological work attributes some 10,000-12,000 deaths to the episode in all.
The government’s first instinct was to minimise — ministers pointed at influenza, and Harold Macmillan resisted demands for action as impractical. Parliament and public pressure won: the Clean Air Act of 1956 created smoke-control zones, pushed households to smokeless fuels, and began the long cleaning of British urban air. The pea-souper, four centuries old, was legislated out of existence within a generation — priced, finally, at its true cost.