Thomas Midgley Jr. had a fever. It was 1923, and the brilliant chemist was shivering in bed, not from the flu, but from lead poisoning. He had spent months trying to solve "engine knock," that annoying rattling sound early cars made when they struggled to burn fuel. He found the solution: Tetraethyl lead (TEL). It worked perfectly. It also became the core of leaded gasoline, a substance that many historians and scientists now consider the worst mistake in the history of the human race.
It wasn’t just a bad business call. It was a global poisoning event that lasted for nearly a century.
We aren't talking about a small oopsie. We’re talking about a decision that lowered the IQ of half the American population, fueled a decades-long crime wave, and pumped millions of tons of a known neurotoxin into the air we breathe.
The Day We Poisoned the Atmosphere
The story starts at General Motors. In the early 1920s, cars were loud and inefficient. Midgley, working under the legendary Charles Kettering, discovered that adding lead to gasoline made engines run smooth as silk. The problem? Everyone already knew lead was toxic.
Roman authors like Vitruvius had written about the "pallid" complexions of lead workers two thousand years ago. But GM, Du Pont, and Standard Oil saw dollar signs. They formed a joint venture called Ethyl Corporation. Notice they didn't call it "LeadCorp." They intentionally dropped the word "lead" from their marketing to avoid scaring the public.
Then people started dying.
At a standard oil refinery in Bayway, New Jersey, workers began hallucinating. They thought they were being chased by giant insects. Others became violently psychotic. Five died within days. Midgley actually held a press conference where he washed his hands in leaded gas and sniffed it for sixty seconds to "prove" it was safe.
He knew he was lying. He had just spent months in Florida recovering from his own lead exposure.
A Half-Century of Brain Damage
When you burn leaded gasoline, the lead doesn't just vanish. It turns into microscopic particles that fly out of the exhaust pipe. You breathe it in. It settles in the soil where kids play. It gets into the dust on your windowsill.
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Once lead enters the human body, it’s a master of disguise. It mimics calcium. Because the body thinks it's a vital mineral, it ushers the lead straight into the brain and bones. In the brain, it wreaks total havoc. It interferes with neurotransmitters and literally shrinks the prefrontal cortex—the part of the brain responsible for impulse control and complex planning.
The numbers are staggering. A 2022 study published in the journal PNAS (Proceedings of the National Academy of Sciences) found that exposure to leaded gasoline robbed Americans born before 1996 of an estimated 824 million total IQ points.
Think about that.
The average person born in the 1960s and 70s lost roughly six to seven IQ points. For those in the highest exposure areas, the loss was even greater. We basically handicapped the collective intelligence of the entire planet for the sake of better engine performance.
The Lead-Crime Connection
There’s a weird pattern in history. In the 1960s, 70s, and 80s, violent crime skyrocketed across the globe. Experts blamed everything: poverty, the breakdown of the nuclear family, pop culture. But economist Rick Nevin and Mother Jones journalist Kevin Drum noticed something else.
The rise and fall of violent crime tracked almost perfectly with the rise and fall of leaded gas usage—with a 20-year lag.
It makes sense. You poison a generation of toddlers with a neurotoxin that destroys impulse control. Twenty years later, those toddlers become young adults. If their "brakes" are biologically broken, they are much more likely to react to conflict with violence.
When the United States started phasing out leaded gas in the 1970s (thanks to the Clean Air Act and the invention of the catalytic converter), crime didn't drop immediately. It took exactly two decades for the "cleaner" generation to grow up. By the early 90s, crime rates began a precipitous, unexplained collapse that continues to baffle some sociologists today.
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But the data is hard to ignore. When you map lead exposure by zip code, it correlates with crime rates more accurately than almost any other variable.
Why We Let It Happen
Money. It’s always money.
Ethanol was actually a viable alternative to lead in the 1920s. It also stopped engine knock. But you can't patent ethanol. You can patent a chemical additive like Tetraethyl lead. The Ethyl Corporation fought tooth and nail for decades to suppress research.
They hired a scientist named Robert Kehoe. He was the "expert" for the lead industry for 50 years. Kehoe pushed the "threshold" theory—the idea that lead was only dangerous if you had enough of it to show immediate symptoms of poisoning. He claimed that because lead was "natural," having it in our blood was normal.
It was the original playbook for climate change denial and tobacco industry lies.
It took a geochemist named Clair Patterson to break the spell. Patterson was trying to calculate the age of the Earth by measuring lead isotopes in zircons. He kept finding that his samples were contaminated. He realized that the entire surface of the planet—and even the deep ocean—was saturated with man-made lead.
Patterson fought the industry for years. They tried to get his funding cut. They tried to get him fired from Caltech. But he didn't back down. Because of him, we finally realized that "normal" lead levels in our blood were actually 100 to 1,000 times higher than they were in our ancestors.
The Long Tail of the Disaster
Even though leaded gasoline is now banned for road vehicles worldwide (Algeria was the last to stop in 2021), the mistake isn't "over."
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Lead doesn't biodegrade. It stays in the dirt. If you live near a busy road that existed in the 1970s, the soil in your backyard likely contains legacy lead. This is why urban gardening requires raised beds and fresh soil.
Furthermore, leaded gas is still used in small piston-engine aircraft. If you live near a small regional airport, you are likely still being exposed to lead. A study of children living near airports in California showed significantly higher blood lead levels compared to those living further away.
What We Can Do Now
You can’t go back and un-breathe the air of 1975. But you can mitigate the ongoing effects. Dealing with the fallout of the leaded gasoline era requires a mix of public policy and personal vigilance.
First, if you live in a home built before 1978, assume there is lead paint. Don't dry-sand it. Don't scrape it without a HEPA vacuum. Lead dust is the primary way kids are poisoned today.
Second, look at your nutrition. Lead competes with calcium and iron. If a child’s diet is rich in calcium, vitamin C, and iron, their body is less likely to absorb lead from the environment. It’s a biological shield.
Third, we need to push for the total elimination of leaded aviation fuel (Avgas). The technology exists. The FAA has a plan to transition by 2030, but the industry moves slowly.
Finally, get your soil tested. If you’re growing tomatoes in an urban lot, spend the 50 dollars for a lab test. It’s the only way to know what’s actually in the dirt.
The leaded gas saga is a brutal reminder of what happens when we prioritize short-term industrial gain over basic biological safety. It wasn't just a mistake; it was a choice made every day for 80 years. We are still living with the cognitive and social consequences of those choices.
Actionable Steps for the Modern World:
- Check Your Pipes: Lead service lines are still common in older cities like Chicago or Newark. Use a high-quality water filter certified to remove lead (look for NSF/ANSI Standard 53).
- Test Your Kids: In many states, lead screening is mandatory at ages 1 and 2. Ensure your pediatrician performs a blood lead level (BLL) test.
- Be Careful With Antiques: Old toys, glazed ceramics from certain countries, and even some vintage "corelle" plates contain high lead levels.
- Support Soil Remediation: Encourage local governments to cap or replace soil in public parks located near old highway interchanges.
The "Lead Era" cost us more than we can ever fully calculate. We lost geniuses who were never born, scientists who lost their edge, and a level of social peace we are only just beginning to recover. Understanding this history is the only way to make sure we don't repeat it with the next "miracle" chemical.