He just wanted to stop the knocking. That’s it. In the early 1920s, internal combustion engines were loud, vibrating messes, and Thomas Midgley Jr., a mechanical engineer at General Motors, thought he had the silver bullet. He found that adding tetraethyllead (TEL) to gasoline made engines run smooth as silk. It was a mechanical triumph and a biological catastrophe.
Honestly, we’re still living with the fallout.
When people talk about the "worst idea" in history, they usually point to New Coke or the Hindenburg. Those were blunders, sure, but they didn't fundamentally alter the chemical composition of the Earth's atmosphere or lower the collective IQ of the entire human race. Midgley’s "invention" of leaded gasoline did exactly that. It wasn't an accident; it was a choice made by powerful people who ignored decades of medical warnings for the sake of a patentable additive.
The Toxic Magic of Tetraethyllead
Engine "knock" isn't just an annoying sound. It’s premature combustion that can literally tear a motor apart. By 1921, the race was on to find an additive that would allow higher compression ratios. Ethanol worked. It worked great, actually. But you can't patent corn alcohol, so there was no money in it for GM or Standard Oil.
Midgley settled on lead.
Lead is a neurotoxin. We've known this since the Romans were lining their aqueducts with it and going mad. But Midgley and his bosses at the newly formed Ethyl Corporation marketed it as "Ethyl," carefully scrubbing the word "lead" from their branding to avoid scaring the public. They knew. They absolutely knew it was dangerous. During production at a plant in Deepwater, New Jersey, workers started acting "funny." Then they started hallucinating. Then they died in straightjackets.
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Midgley himself had to take a long vacation to Florida to recover from lead poisoning. Yet, in 1924, he held a press conference where he washed his hands in TEL and sniffed it for sixty seconds to prove its safety. It was a lie. He was secretly suffering from the effects while he smiled for the cameras.
Why Leaded Gasoline Is the Worst Idea of All Time
It’s hard to wrap your head around the scale of the damage. For sixty years, every time someone drove to the grocery store, they were spewing microscopic particles of a permanent brain poison into the air. This wasn't localized. It settled in the soil where kids played. It got into the dust on windowsills.
If you were born between 1951 and 1980, you likely lost several IQ points because of Thomas Midgley Jr. Research published in the Proceedings of the National Academy of Sciences (PNAS) estimates that leaded gas stripped over 800 million cumulative IQ points from the American population alone. That is a staggering, almost incomprehensible statistic.
The Crime Link
There’s a fascinating, albeit controversial, theory called the Lead-Crime Hypothesis. It suggests that the surge in violent crime in the 1960s, 70s, and 80s wasn't just about social policy or economics. It was about lead. Because lead exposure during childhood damages the parts of the brain responsible for emotional regulation and impulse control, a whole generation grew up more prone to aggression.
When lead was finally phased out in the 1990s—thanks to the tireless work of scientists like Clair Patterson—violent crime rates plummeted globally. It’s one of the most consistent correlations in environmental sociology. We poisoned the kids, and then we wondered why the world got more violent.
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The Man with the Midas Touch for Disaster
Midgley didn't stop at leaded gasoline. He was a busy man.
He also invented Freon (CFCs). At the time, refrigerators used dangerous gases like ammonia or sulfur dioxide that could kill a family if they leaked. Midgley wanted something "safe." Freon was non-flammable and non-toxic to breathe, so it seemed like a win.
It just happened to eat a hole in the ozone layer.
Environmental historian J.R. McNeill famously remarked that Midgley "had more impact on the atmosphere than any other single organism in Earth's history." It’s an impressive, terrifying resume. One man, two inventions, and a planet struggling to recover from both nearly a century later.
The Slow Walk to Reform
Why did it take so long to stop? Money.
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The Ethyl Corporation had a stranglehold on the market. They funded the "research" that claimed low-level lead exposure was natural. They attacked anyone who suggested otherwise. It took Clair Patterson, a geochemist who was actually trying to measure the age of the Earth, to blow the whistle.
Patterson realized he couldn't get an accurate measurement of lead isotopes because his entire lab was contaminated by the lead in the air outside. He had to build one of the world's first "clean rooms" just to do his job. When he started comparing deep-ocean sediments to surface water, he found that lead levels in the environment had spiked by massive amounts since the introduction of leaded gasoline.
The industry tried to ruin him. They pressured his university to fire him. They cut off his funding. But facts are stubborn things, and by the late 70s, the EPA finally began the phase-out.
What We Can Learn From This Mess
Midgley wasn't a "villain" in a cape. He was an engineer solving a specific technical problem without looking at the system as a whole. He focused on the engine, ignored the exhaust, and dismissed the biology.
This is the quintessential "worst idea" because it was a series of successful short-term solutions that created a long-term existential crisis. We see this today with plastic pollution and certain AI developments. We solve for "X" (knocking engines/convenience/speed) while ignoring "Y" (global health/ecological collapse).
How to Protect Yourself Today
While leaded gasoline is banned for cars in almost every country now (Algeria was the last to stop in 2021), the legacy remains. You can't just "un-lead" the planet.
- Test your soil: If you live in an old urban area or near a highway built before 1980, your garden soil likely contains high levels of lead. Don’t grow root vegetables in it without a raised bed and fresh soil.
- Check your pipes: In many older cities, lead service lines still deliver water. Use a high-quality filter certified to remove lead (look for NSF/ANSI Standard 53).
- Dust is the enemy: In old homes, lead-based paint and legacy lead dust from the "Ethyl" era are the primary risks. Regular wet-mopping and HEPA vacuuming are non-negotiable for families with small children.
- Aviation Fuel: Small piston-engine planes (General Aviation) still use leaded fuel (100LL). If you live directly under a flight path of a small regional airport, your local air quality may still be impacted by the very same "worst idea" Midgley cooked up in 1921.
The story of Midgley and leaded gasoline serves as a permanent warning. Innovation without ethics isn't progress; it's just a very expensive way to break the world.