Skip to main content

Quirk of history

History’s most prolific killer

Robert Alexander/Getty

Who do you think is responsible for the most deaths in human history, asks Brian Klaas on Substack. Mao? Stalin? Hitler? In fact, “it’s someone you’ve probably never heard of”: an American chap called Thomas Midgley Jr. In 1921, Midgley discovered that adding a chemical compound called tetraethyl lead to petrol prevented a common fault in combustion engines. Everyone knew that lead itself was toxic, and that in high concentrations could send people mad – a tetraethyl lead plant in New Jersey was openly known as the “loony gas building”. But General Motors desperately needed the compound to make its cars function, so “the poison spread”.

In the 1990s, when the government finally began banning leaded petrol, an American researcher called Rick Nevin noticed a troubling trend: violent crime rates in the US followed almost exactly the same trajectory as atmospheric levels of lead. The only difference was time period: the rise and fall in violence came 20 years after the corresponding changes in lead levels. There was other evidence of a link: a sharp rise in murders in St Louis, Missouri two decades after a huge lead smelter opened there; a nationwide spike in violence after leaded paint became more common. The consequences of all this are staggering: it is now thought that lead poisoning “caused more than 100 million deaths worldwide”. All, arguably, thanks to Mr Midgley.

🛌💀 Leaded petrol wasn’t the only horror for which Midgley was responsible. He later invented some of the first CFCs, the chemicals that “punched an enormous hole in the Ozone layer”. And after contracting polio in 1940, he created an “elaborate system of pulleys and ropes to lift himself out of bed” – only to get entangled in the contraption and die from strangulation.