Thomas Midgley Jr.: The Inventor of Leaded Gasoline and CFCs

One scientist created two inventions that unintentionally caused the deaths of millions of people. These inventions not only decreased the average IQ globally but also contributed to an increase in crime rates and sparked two distinct environmental disasters that continue to impact the world today.

In 1944, a young chemist named Clair Patterson joined the Manhattan Project, contributing to the development of the first nuclear weapons. His role involved concentrating uranium-235 from the more common uranium-238 for use in bombs. He used spectrometers to separate the two isotopes based on their slight difference in mass. After the war, Patterson returned to graduate school to pursue his PhD, choosing a course of study that leveraged his expertise with mass spectrometers: measuring the age of the Earth.

Radioactive rocks are used to determine the Earth's age because uranium decays through a series of steps—starting with thorium and protactinium and undergoing 12 more decays—before ending at stable lead-206. This rate of decay is consistent and measurable. It takes 4.5 billion years for half of a uranium sample to decay into lead. Clair Patterson decided to use zircon crystals for his research because these crystals naturally contain traces of uranium but no lead when they form. Therefore, any lead present in the crystals must result from uranium decay. Patterson was tasked with measuring the lead content, while another student, George Tilton, measured uranium. Tilton's uranium results aligned with expectations, but Patterson's lead measurements were inconsistent and significantly higher than expected. They concluded there was extra lead in the samples that didn’t belong. But where was all this lead coming from?

In 1908, a woman was driving across the Belle Isle Bridge in Detroit when her car stalled. A passing driver stopped to help. In those days, cars had a hand crank that needed to be inserted at the front to start the engine. The man knelt down to start the crank, but the engine started too quickly and jolted forward. The crank struck him in the face, breaking his jaw. He later died from the injury. His name was Byron Carter, the founder of his own car company. Byron was a well-connected man, even being a close friend of Cadillac founder Henry Leland. Leland was so devastated by the death of his friend that he sought to eliminate hand cranks from cars.

He hired Charles Kettering to create a self-starting car. By 1911, Kettering had developed a working prototype, the Cadillac Model 30. It was much faster than most cars at the time, with a top speed of 45 miles per hour and 40 horsepower—double that of the Ford Model T. The car was a success, doubling the company's income, but it had a huge problem: it was deafeningly loud. In an internal combustion engine, a piston compresses the fuel-air mixture, which is then ignited by a spark from the spark plug. The expanding hot gases push the piston down, causing the car to move. The problem with the Model 30 was that it compressed the fuel-air mixture more than previous models, to the point where the fuel would spontaneously combust before the spark from the spark plug could ignite it. Instead of perfectly timed explosions, multiple combustions occurred, leading to loud bangs. This issue became known as engine knocking. It was not only loud but also detrimental to engine performance. It reduced power output, lowered fuel efficiency, and the vibrations from the knocking damaged the pistons, shortening the engine's lifespan.

However, the knocking could be solved by changing the fuel. Since different fuels can handle varying levels of compression before combusting, fuels with higher pressure resilience are less likely to cause knocking. Kettering wanted to find an additive that would increase the pressure resilience of standard fuel, so he hired 27-year-old engineer Thomas Midgley Jr. to find such an additive. Midgley experimented with various substances, from melted butter and camphor to ethyl acetate and aluminum chloride. Later, he would write that most of them had no more effect than ‘spitting in a great lake.’ Tellurium worked, but it had a terrible smell that wouldn’t come off even after bathing. His wife was so repulsed by the smell that she made him sleep in the basement for seven months. On December 5th, 1921, after five years of experimentation, Midgley believed he had found the perfect solution: tetraethyl lead. It stopped the knocking, was cheap to produce, didn’t smell, and only required one part of tetraethyl lead per 1,000 parts of fuel.

Kettering and Midgley patented the process and called it 'Ethyl,' but they made no mention that it contained lead. They partnered with General Motors, DuPont, and Standard Oil of New Jersey to form the Ethyl Corporation. The demand skyrocketed, and they had to build a second factory. However, many workers fell ill with lead poisoning. To address the public outcry, Midgley held a press conference where he poured leaded gasoline on his hand and inhaled the fumes for a full minute. He claimed he could do this daily with no ill effects.

Lead in the body is dangerous because it mimics calcium, and as a result, the body doesn't have a natural way to eliminate it. Like calcium, lead is stored in the bones for years, continuing to poison the body long after the initial exposure. The organ most susceptible to lead poisoning is the brain. Lead breaks down the myelin sheath around axons and interferes with the release of neurotransmitters, which can cause memory loss, learning disorders, and behavioral changes. MIT, Harvard, and Yale universities warned Midgley about the dangers of lead, but their concerns were ignored.

By the 1950s, millions of cars were using leaded gasoline, which released lead into the atmosphere, some of which landed on Patterson's zircon crystals. By this time, concerns about lead were at an all-time high, but the president of Standard Oil refused to stop producing it. The founders of the Ethyl Corporation claimed that lead was a natural part of the environment and therefore not harmful to humans. However, Patterson questioned how natural the lead in our environment actually was. He measured lead content in the ocean, hypothesizing that if it was natural, the concentration would remain consistent at all depths. But if lead pollution had increased recently, the concentration would be higher near the surface. He took samples from the Atlantic and Pacific Oceans down to depths of 4 kilometers, and sure enough, lead levels were ten times higher at the surface. Patterson now knew that lead content was not natural, but he wanted to determine when the pollution had started.

So, Patterson traveled to Antarctica and Greenland. Ice cores record levels of lead in the air going back thousands of years, and the levels of lead have been increasing for the past 4,500 years, primarily due to human activity, especially smelting ores. Patterson concluded that lead levels had been rising steadily since the 1920s. He then examined the levels of lead in the teeth and bones of recently deceased Americans and compared them with the bones of mummies. He expected to find that Americans had 100 times the amount of lead, but the results showed it was closer to a factor of 1,000. There is no safe level of lead exposure. Lead is thought to be the cause of two-thirds of all unexplained intellectual disabilities.

A study in 2022 revealed that half of all people in the USA were exposed to high levels of lead, particularly those born between 1950 and 1980. The author of the study estimated that lead exposure caused the loss of 800 million IQ points. The USA experienced an increase in crime between the 1970s and 1990s, followed by an abrupt decline. A study of 340 teenagers found that those who were arrested were four times more likely to have elevated lead levels in their bones. In the USA alone, the death toll from lead exposure is thought to be around 25 million, and worldwide, it’s estimated to be 100 million—all because Midgley introduced a chemical that we knew was toxic into fuel. Today, one in three children globally, or 800 million children, could have dangerously high lead levels.

After his work with leaded gasoline, Midgley was put in charge of another project. GM wasn’t just making cars, but also household appliances, and fridges had a problem: the two most common refrigerant gases, methyl formate and sulfur dioxide, were either toxic or flammable. Midgley was tasked with creating a safer solution. In 1928, he developed dichlorodifluoromethane, which GM branded as Freon. To prove its safety, Midgley inhaled a lungful of the gas and blew out a candle. Freon became very popular and was used as a solvent and in aerosols. However, when Freon is released into the atmosphere, it is hit by UV rays, causing the chlorine to break away. This chlorine then reacts with the ozone layer, destroying it and increasing the amount of UV radiation humans are exposed to, which raises the risk of skin cancer. Chlorine is also a greenhouse gas, and it is 10,000 times more warming than carbon dioxide.

An act was passed in 1989 to ban Freon, and there are signs that the ozone layer is recovering, but it will still take decades for it to fully heal. In 1940, at the age of 51, Midgley contracted polio and became physically disabled. To help himself get out of bed, he created a series of ropes and pulleys. However, in 1944, while using this contraption, he became tangled and died of strangulation. In 1986, leaded gasoline began to be banned, with Algeria being the last country to do so in 2021.