In the early 1920s, car engines had a problem. Under strain they knocked, a violent rattling that could shake an engine to pieces. At General Motors, an engineer named Thomas Midgley Jr. was told to stop it. He and his team tested tens of thousands of chemical compounds, hunting for something to add to petrol that would calm the engine. The reward was enormous, because a quiet engine could be built twice as powerful. Midgley found his answer. Years later he found a second one, for a different problem. Both were hailed as triumphs. Both turned out to be poisons that spread around the entire planet. This is the story of one inventor and two chemicals, and of how long it took the world to notice what they were doing. The first question is simple. What exactly did Midgley put into the petrol?
Thomas Midgley: The Man Who Poisoned the Planet Twice
Midgley added lead to petrol in 1921 and invented CFCs in 1928, and both chemicals went on to poison the planet.
A Knock in the Engine
Frequently Asked Questions
What did Thomas Midgley invent that harmed the planet?
Midgley found that tetraethyl lead stopped engine knocking, and it was sold as the petrol additive Ethyl. Later he helped create Freon, the first chlorofluorocarbon. Lead spread through the air, soil and people, and CFCs ate away the ozone layer.
How did the world find out that leaded petrol had contaminated the whole planet?
Geochemist Clair Patterson was trying to date the Earth when he found almost no lead in deep ocean water but a great deal at the surface. Bones from Peru showed what natural lead levels in people had been. His data showed modern people carried more than 500 times that level.
When did leaded petrol finally end?
The United States banned it for road vehicles on January 1, 1996. Algeria became the last country to stop selling it in July 2021, nearly a century after its discovery. CFCs were phased out under the 1987 Montreal Protocol and replaced by HFCs, which spare the ozone but are potent greenhouse gases.
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