Chapter Content
Okay, so, uh, this is about getting the lead out, basically. So, back in the late 1940s, this grad student at the University of Chicago, name of Clair Patterson, even though he was, like, a farm kid from Iowa, was trying to, you know, nail down the exact age of the Earth using this newfangled lead isotope measurement thing. But, like, all his rock samples were, totally contaminated, you know? Like, *really* contaminated. Most of 'em had, like, 200 times the normal level of lead.
And, it took him years, seriously years, to figure out that the problem was, get this, this guy from Ohio, Thomas Midgley Jr. Now, Midgley was a trained engineer, and honestly, the world probably would have been better off if he'd just stuck with engineering. But, no, he got all interested in industrial uses for chemistry. So, in 1921, while he was working at General Motors Research Corporation in Dayton, Ohio, he, like, discovered that this compound, tetraethyl lead, could seriously reduce engine knocking. You know, that pinging sound?
So, even back then, early 1900s, people knew lead was bad news, but it was still everywhere. Canned food, sealed with lead solder. Water, stored in lead-lined tanks. Lead arsenate, sprayed on fruit as pesticide. Even in freakin' toothpaste tubes! Like, everything was giving you a little dose of lead. But the biggest, the thing you were exposed to the *most*, was leaded gasoline.
And lead, well, it’s a neurotoxin. Too much in your system, and it messes up your brain and nervous system, like, permanently. Lead poisoning could cause all kinds of nasty stuff, vision loss, insomnia, kidney failure, deafness, cancer, paralysis, seizures. And, in severe cases, you could just, like, suddenly start hallucinating, which is scary for everyone involved. Usually that leads to coma or death, like, nobody wants that, right?
But, on the other hand, lead is super easy to refine and mine, and mass production was, like, crazy profitable. And tetraethyl lead really *did* stop engine knocking. So, in 1923, these three huge companies – General Motors, DuPont, and Standard Oil of New Jersey – they teamed up and created this joint venture, the Ethyl Gasoline Corporation. Later, they just shortened it to Ethyl Corporation. And they produced as much tetraethyl lead as the world wanted. Which turned out to be a *lot*. They called it "Ethyl" because, you know, sounded better than "lead," which, you know, screamed poison.
February 1st, 1923, they started pushing this name on the public, getting them to accept it. And, oh boy, that was a bad idea.
Almost immediately, the workers on the front lines started getting all wobbly and confused, you know, classic signs of lead poisoning. And Ethyl Corporation, they just denied everything. Like, pretending nothing was wrong, and they got away with it for decades. This historian, Sharon Bertsch McGrayne, she wrote that if factory workers started getting hallucinations, the company spokesman would just, like, straight-faced, tell reporters, "Oh, they're just overworked." Seriously! In the early days of leaded gasoline production, at least 15 workers died, and countless others got sick, usually really sick. The real numbers are, like, impossible to know, because the company almost always covered things up, never reported spills or poisonings. But sometimes, it was impossible to hide. Like, in 1924, five workers died and 35 were permanently disabled in just a few days in one badly ventilated factory.
So, rumors started spreading that this new product was dangerous, and to calm everyone down, Thomas Midgley, the guy who invented it, decided to do a demonstration for the press. He talked about how safe the company was making everything, and then he poured leaded gasoline all over his hands. And then, get this, he put a beaker of it under his nose for 60 seconds, claiming he could do that every day and be fine. But, Midgley knew how dangerous lead was. He'd gotten really sick from it a few months earlier, and he wasn't going anywhere near that stuff unless he absolutely had to, especially in front of reporters.
Leaded gasoline was a huge success, and Midgley, he was all encouraged, so he decided to tackle another problem of the time. Refrigerators back in the 1920s used toxic, dangerous gases that leaked all the time. Like, a hospital leak in Cleveland in 1929, killed over 100 people. So Midgley set out to invent a gas that was stable, non-flammable, non-corrosive, and safe to breathe. And with his history of, like, zero regrets, he invented chlorofluorocarbons, or CFCs.
And, like, almost no industrial product has ever been accepted so quickly and turned out to be so awful. CFCs went into production in the early 1930s, and they were used for everything, from car air conditioners to deodorant sprays. And then, like, half a century later, we found out they were eating away the ozone layer in the stratosphere. Which, you know, not a good thing.
Ozone is just a form of oxygen, but instead of two atoms per molecule, it has three. And it’s kinda weird chemically. It's a pollutant at ground level, but up in the stratosphere, it's what protects us from dangerous ultraviolet radiation. And there's not that much of it, really. Even if it was spread out evenly in the stratosphere, it would only be about two millimeters thick. Which is why it's so easy to disrupt it.
And the amount of CFCs wasn't that much either – only about a billionth of the total atmosphere – but, man, that stuff was powerful. A kilogram of CFCs could capture and destroy 70,000 kilograms of ozone in the atmosphere. And CFCs stick around for a long time, like, a century on average, just causing damage. And they trap heat. One molecule of CFC can increase the greenhouse effect about 10,000 times more than one molecule of carbon dioxide, which itself is a pretty good greenhouse gas. So, CFCs might end up being the worst invention of the 20th century.
And, you know, Midgley never lived to find that out. He died before anyone realized how bad CFCs were.
And, his death was super weird too. He got polio and became disabled, so he invented this mechanical device to help him get out of bed. But in 1944, the machine malfunctioned, and he got tangled in the ropes and suffocated. Seriously.
Okay, so if you were into dating things, the University of Chicago in the 1940s was the place to be. Willard Libby was about to invent radiocarbon dating, which would let scientists figure out the age of bones and other organic remains, like, precisely, which they couldn't do before. Before that, the reliable dates only went back to the First Dynasty of Egypt – around 3000 BC. Nobody really knew when the last ice sheets retreated, or when the Cro-Magnons in France painted the Lascaux caves.
Libby's method was a game changer, and he won the Nobel Prize in 1960 for it. It's based on the idea that all living things have a carbon isotope inside them called carbon-14, and when they die, that isotope starts decaying at a measurable rate. Carbon-14 has a half-life of about 5,600 years, which means it takes that long for half of any sample to disappear. So, by figuring out how much a sample has decayed, Libby could pretty accurately date things, within limits. After eight half-lives, only 0.39% of the original carbon-14 is left. Which is too small to measure reliably, so carbon-14 dating only works for things that are less than about 40,000 years old.
But, as the technology got used more and more, some problems started popping up. First, they realized that this basic number in Libby's formula, the decay constant, was off by 3%. And thousands of calculations had already been done by then! So, scientists didn't correct all the calculations, they just decided to keep the inaccurate constant. And, as this guy Tim Flannery said, you just have to subtract about 3% from every radiocarbon date you see today.
And, that wasn't the only issue. They also discovered that carbon-14 samples are really easy to contaminate with carbon from somewhere else. Like, a tiny bit of plant material getting mixed in with the sample. For younger samples, under about 20,000 years, a little contamination isn't a big deal. But for older samples, it's a huge problem, because there are so few original atoms left. To quote Flannery again, in the first case, it's like losing a dollar out of a thousand, and in the second, it's like losing a dollar out of only two.
And Libby's method was also based on the assumption that the amount of carbon-14 in the atmosphere, and how fast living things absorb it, has always been the same. But that's not true either. We now know that the amount of carbon-14 in the atmosphere changes depending on how well Earth's magnetic field deflects cosmic rays, and the changes can be pretty big over long periods of time. Which means some carbon-14 dates are less reliable than others. And, one of the periods that's less reliable is around when humans first arrived in the Americas. Which is why that issue is always being debated.
And finally, kinda surprisingly, the results can be totally skewed by things that seem totally unrelated, like, animal diets. There's this big debate about whether syphilis came from the New World or the Old World. Archeologists in Hull found monks in a monastery graveyard who had syphilis. So, the initial conclusion was that syphilis was around before Columbus. But that got questioned because scientists found that the monks ate a lot of fish, which made their bones look older than they actually were. So, the monks might have had syphilis, but how and when they got it, well, that's still up in the air.
Because of all the problems with carbon-14 dating, scientists invented other ways to date old stuff, like thermoluminescence dating and electron spin resonance. Thermoluminescence dating measures the number of electrons trapped in the soil, and electron spin resonance bombards a sample with electromagnetic waves to measure electron vibrations. But even with the best methods, you can't date anything older than about 200,000 years, and you can't date inorganic stuff like rocks at all. Which is a problem when you're trying to figure out the age of the planet.
And the problem with dating rocks, well, almost everyone gave up on it for a while. Except for this one really determined British professor, Arthur Holmes.
Holmes was a hero, both in terms of overcoming obstacles and in terms of what he accomplished. Back in the 1920s, when his career was taking off, geology wasn't a popular science anymore. Physics was the hot thing, and funding was really tight, especially in Britain. For years, he was the *only* person in the geology department at Durham University. And to do his rock dating work, he often had to borrow or build his own equipment. He had to wait a year for the school to get him a simple adding machine. Sometimes he had to stop his academic work completely to earn money for his family. He even opened an antique shop in Newcastle, and sometimes he couldn't even afford the five-pound annual fee for the Geological Society.
The method Holmes used was actually pretty simple in theory. It was based on the process that Ernest Rutherford discovered in 1904, that some atoms decay from one element to another at a predictable rate, so you can use that process like a clock. If you know how long it takes for potassium-40 to turn into argon-40, and you measure how much of each element is in a sample, you can figure out the age of the material. Holmes's contribution was to measure the rate at which uranium decays into lead to date rocks, which he hoped would let him date the Earth.
But, there were a lot of technical difficulties. Holmes needed an advanced instrument that could precisely measure tiny samples, and we know he barely had an adding machine. So it was pretty amazing that he was able to announce with confidence in 1946 that the Earth was at least 3 billion years old, and probably older. It was a huge achievement. But he ran into another problem: his colleagues were super conservative and refused to believe him. A lot of people liked his method, but they thought he was dating the materials that made up the Earth, not the Earth itself.
And that's where this guy at the University of Chicago, Harrison Brown, comes in. He invented a new way to measure lead isotopes in igneous rocks, rocks formed by heating instead of sedimentation. And because he thought the work was kind of boring, he gave it to this young guy, Clair Patterson, as his thesis project. He promised Patterson that using his new method to date the Earth would be a snap. Actually, it took years.
Patterson started the project in 1948. Compared to Thomas Midgley's, you know, colorful and disastrous contributions, Patterson's work on dating the Earth was kind of, well, mundane. For seven years, first at the University of Chicago, then at Caltech, where he moved in 1952, he worked in a sterile lab, carefully selecting samples of old rocks and precisely measuring the ratio of lead to uranium.
The problem with dating the Earth is that you need really old rocks that contain crystals with lead and uranium, rocks that are almost as old as the planet itself. If the rocks are much younger, you'll obviously get a younger date, and that'll give you the wrong answer. But really old rocks are really hard to find on Earth. Back in the 1940s, nobody knew why. It wasn't until the Space Age that anyone had a decent explanation for where Earth's old rocks went. (The answer is plate tectonics, but, you know, we'll get to that.) In the meantime, Patterson had to figure it all out with very little to work with. Finally, he had this stroke of genius: he realized that he could use rocks from outside Earth. He turned his attention to meteorites.
He made this assumption, a pretty visionary one that turned out to be right, that a lot of meteorites were actually building blocks left over from the early solar system. And so they retained their original internal chemistry. Date those wandering rocks, and you've dated, or nearly dated, the Earth.
But as usual, easier said than done. Meteorites aren't exactly common, and it's not like you can just walk up and grab one. And Brown's measurement methods were too detailed and needed a lot of improvement. And the biggest problem was that Patterson's samples were constantly getting contaminated by lead in the atmosphere. Which is why he ended up building a sterilized lab, the first sterile lab in the world.
Patterson worked away at it for seven years before he had samples he could use for the final test. In the spring of 1953, he sent the samples to the Argonne National Laboratory in Illinois. And he got access to this new mass spectrometer that could find and measure tiny amounts of uranium and lead hidden in ancient crystals. Patterson finally got his results. He was so excited that he drove straight to his childhood home in Iowa, and his mother had to take him to the hospital because he thought he was having a heart attack.
Shortly after that, at a conference in Wisconsin, Patterson announced that the Earth was 4.55 billion years old, give or take 70 million years. And as McGrayne said, that number has stood for 50 years. After 200 years of effort, the Earth finally had an age.
Patterson almost immediately turned his attention to the problem of lead in the atmosphere. He was shocked to find out that almost everything people thought they knew about the effects of lead was wrong, or misleading. Which isn't surprising, because for 40 years, every study on lead's effects had been funded by the lead additive manufacturers.
One of these studies involved a doctor with no training in chemical pathology. The doctor had volunteers inhale or swallow increasing amounts of lead and then tested their poop. Which, uh, the doctor didn't seem to know that lead isn't excreted as waste, it builds up in your bones and blood, which is why it’s so dangerous. He didn't check bones or blood. And so, lead was declared to be harmless.
Patterson quickly realized that there was a *ton* of lead in the atmosphere, and actually there still is a ton, because lead never disappears. And about 90% of it came from car exhaust. But he couldn't prove it. He needed a way to compare the current level of lead in the atmosphere with the level before tetraethyl lead went into commercial production in 1923. And then he had this idea that ice cores might provide the answer.
People knew that in places like Greenland, the layers of snow are distinct each year. Because the seasonal changes make the colors a little different. By counting those layers and measuring the amount of lead in each layer, you can calculate the amount of lead in the global atmosphere at any time over hundreds or even thousands of years. This idea became the basis for ice core research. It’s the basis for a lot of modern climate science.
Patterson found that before 1923, there was almost no lead in the atmosphere. And since then, the concentration had climbed dangerously.
So getting the lead out of gasoline became his life's mission. And he frequently criticized the lead industry and its lobbyists, often in pretty harsh terms.
And it turned out to be a brutal fight. The Ethyl Corporation was a huge company with a lot of friends in high places. (Its directors included Supreme Court Justice Lewis Powell and Gilbert Grosvenor of the National Geographic Society.) Patterson suddenly found that his research funding was either being revoked or really hard to get. The American Petroleum Institute canceled a contract with him, and so did the U.S. Public Health Service, which was supposed to be a neutral government agency.
Patterson became a liability to his university. Officials from the lead industry kept pressuring the Caltech board of trustees to either shut him up or fire him. Jamie Lincoln Kitman wrote in The Nation in 2000 that Ethyl Corporation was supposedly willing to donate a professorial chair to Caltech, “if it would facilitate Patterson’s departure.” Ridiculously, an American Research Committee panel was assigned to investigate the dangers of lead poisoning in the atmosphere, and he was excluded from it, even though he was by far the leading expert on atmospheric lead in the U.S.
Luckily, Patterson never gave up. Thanks to his efforts, the Clean Air Act of 1970 was passed, and the U.S. stopped selling leaded gasoline in 1986. Almost immediately, the level of lead in Americans' blood dropped by about 80%. But because lead is so persistent, every living American today still has about 625 times more lead in their blood than people did a century ago. And the amount of lead in the atmosphere is still increasing by about 100,000 tons per year, completely legally, mainly from mining, smelting, and industrial activities. The U.S. also banned lead in household paints, as McGrayne put it, “44 years later than most European nations.” Incredibly, given lead's toxicity, the U.S. didn't stop using lead solder in food cans until 1993.
As for Ethyl Corporation, it’s still around, even though General Motors, Standard Oil, and DuPont don't own it anymore. (They sold their shares to Albemarle Paper Company in 1962.) According to McGrayne, as late as February 2001, Ethyl Corporation was still claiming that, “studies indicate that leaded gasoline poses no threat to human health or the environment.” On its website, the company's history doesn't mention lead, or George Midgley. It just says that its original products contained “a chemical mixture.”
Ethyl Corporation doesn't make leaded gasoline anymore, but according to its 2001 report, sales of tetraethyl lead still amounted to $25.1 million in 2000, slightly up from $24.1 million in 1999, but down from $117 million in 1998. The company said in its report that it was determined to “maximize the cash flow generated by tetraethyl lead, despite declining worldwide usage.” Ethyl Corporation sells tetraethyl lead worldwide through an agreement with Associated Octel Company in the U.K.
And as for George Midgley's other creation, CFCs, the U.S. banned them in 1974, but they're stubborn little devils. The stuff that's been released into the atmosphere, say from deodorant or hairspray, is almost certainly still up there, eating away at the ozone long after you and I are gone. And even worse, we're still releasing a lot of CFCs into the atmosphere every year. Wayne Biddle says that over 27 million kilograms of CFCs are still being sold every year, worth $1.5 billion. So, who's making CFCs? Well, *we* are. Meaning a lot of big companies are still making it in their overseas factories. Third World countries won't ban them until 2010.
Clair Patterson died in 1995. He didn't get a Nobel Prize for his work. Geologists never do. And even though he worked tirelessly for half a century and made huge, selfless contributions, he didn't get much fame or even recognition. We have every reason to think he was the most influential geologist of the 20th century. But who's ever heard of Clair Patterson? Most geology textbooks don't mention his name. And two recent bestselling histories of dating the Earth even misspelled his name. In early 2001, someone wrote a book review of one of those books in Nature magazine, and they made the incredible mistake of thinking that Patterson was a woman.
But anyway, thanks to Clair Patterson's work, by 1953, the Earth finally had an age that everyone could agree on. Now the only question is, is it older than the world around it?