81. Thallium: It Rides A Pale Horse

In which we learn how reading mystery novels might very well save a life.

Featured above: The Teacup Poisoner himself, Graham Frederick Young.

Show Notes

Show notes and references are forthcoming, per the unfortunate usual. As far as why the CIA wanted to dose Castro with thallium, the answer, of course, is “to kill him.” Secondarily, they knew that on his way to the grave, all his hair would fall out — especially his beard hair. It seems that the insult was just as desirable as the injury.


Episode Script

Englishman William Crookes was still a relatively young chemist when he peered down his spectroscope and observed a bright green line that no one had ever seen before. Perhaps because it was springtime, the color reminded him of a plant’s bright shoot newly sprouting from the ground. He named this new element thallium, after the Greek word for such a sprig, and immediately announced his discovery in the weekly chemistry publication that he edited, Chemical News.1

Completely independently, Claude-Auguste Lamy made the same discovery concurrently on the other side of the Channel. Lamy was actually able to scrape together enough material to cast a little ingot of the new element, a feat Crookes had not yet accomplished. He sent off the metal to be displayed at the 1862 London International Exhibition. It was a smash hit. The organizers were proud to show off a new element, and they awarded Lamy a special medal for chemical innovation.2

When Crookes learned about all this, he was outraged. He spent the next several months lambasting Lamy in Chemical News and demanding that the medal be revoked and given to him instead. Eventually, the exhibition’s organizers decided that Crookes really did deserve a medal of his own, although they let Lamy keep his medal, too.

Perhaps Crookes’ way of going about things comes off as querulous. But perhaps the exhibition committee and Lamy were pretty fortunate, all things considered. Historically speaking, when it comes to jealous disputes involving thallium, at least one of the parties tends to wind up dead.

You’re listening to The Episodic Table Of Elements, and I’m T. R. Appleton. Each episode, we take a look at the fascinating true stories behind one element on the periodic table.

Today, we’re cracking the case of thallium.

We’ve dealt with plenty of toxic elements before, but none quite like thallium. It’s used in a few kinds of specialty glass, and one of its isotopes can be used to diagnose heart problems, but neither of those is very common.3 Since its discovery, thallium has mostly been used as poison. It’s such an incredibly lethal substance, and so rarely tested for, that it’s known as “the poisoner’s poison” — top-shelf stuff, the kind of toxin that can really garner a person a lot of clout in the murder scene. (Presumably.)

In episode 19, we learned how potassium is critical for the function of basically all animal biology. Thallium is so incredibly toxic because the body can’t tell it apart from potassium. The body scoops up thallium and tries to use it the same way as potassium, but it doesn’t work. It’s kind of like pouring milk in your car’s gas tank: You can do it; the gas tank is capable of holding a gallon of milk, but your car can’t use it to go. In fact, it’ll probably ruin your engine.5

Whatever thallium’s body count may be, it’s almost certainly lower than its more notorious counterparts, such as arsenic. (See episode 33 for tales involving that more mainstream toxin.) Along with its lack of name recognition, thallium has never been as widely available as other poisons. After a spate of highly publicized accidental poisonings, its production and its use as a pesticide were banned in several countries.6 7

If you’re reading through the works of Agatha Christie, you might want to pause the episode now and come back after you’ve finished. Thallium, you see, is the weapon of choice in her 1961 novel, The Pale Horse.

In that tale, some suspicious deaths are attributed to three enigmatic “witches” who spend most of their time in a pub. There is no dark magic afoot, of course, and in fact the witches are guilty of nothing more than being rather eccentric. The novel’s hero pieces it all together not a moment too soon:

I dialed a number and was lucky enough this time to get Lejeune straight away.

“Listen,” I said, “is Ginger’s hair coming out by the roots in handfuls?”

“Well – as a matter of fact I believe it is. High fever, I suppose.”

“Fever my foot,” I said. “What Ginger’s suffering from, what they’ve all suffered from, is thallium poisoning. Please God, may we be in time…”

You’ll be happy to know that Ginger ends up just fine.

It seems that most people who know anything about thallium learned about it from Mrs. Christie — and more than one life has been saved because of it. A reader from South America wrote a letter to Christie in 1975, saying, “Of this I am quite, quite certain – had I not read The Pale Horse and thus learned of the effects of thallium poisoning, X would not have survived; it was only the prompt medication which saved him; and the doctors even if he had gone to hospital, would not have known in time what the trouble was.”8

Two years later, a 19-month-old girl was brought to Hammersmith Hospital in West London displaying inscrutable symptoms. The doctors drew blood and performed a lumbar puncture, a full-body x-ray, and an electroencephalogram, all to no avail. The prognosis was looking pretty grim… until Marsha Maitland, one of the hospital’s nurses, overheard the doctors talking about the case.9 10

Incredibly, she just so happened to have recently read The Pale Horse, and she recognized the child’s symptoms as thallium poisoning. Like the hero of Christie’s novel, Maitland swooped in just in the nick of time. A test confirmed elevated levels of element 81 — the girl had probably gotten into some pesticide the family had under the sink. The doctors administered the antidote for thallium, and after a few months she made a full recovery.

Christie possessed rather extensive chemical knowledge, partly due to her time serving as a nurse in both World Wars. But this particular story might have been inspired by a headline from a few years earlier.11

Nikolai Khokhlov was a Soviet who came of age during World War II. He was selected for clandestine assassination missions before he was even twenty years old. One of his first assignments would’ve had him perform as part of a vaudeville quartet, putting on a show for Nazi soldiers who were occupying Moscow. “Germans like art, especially if it is not too serious,” his superior officer explained. Khokhlov was chosen for his ability to whistle. Others were noted singers and comedians, and the fourth member of the group was known simply as “Nina the Juggler.” She was meant to keep an eye out for Nazi VIPs in the audience — possibly even Hitler himself, or at least they hoped.

Nina’s juggling pins would be loaded with explosives, and her job was to lob them out into the crowd and take out as many fascists as possible.

Alas, this scenario never came about. Another Soviet asset spilled the beans, and the Nazis soon retreated from Moscow anyway. Khokhlov and his comrades were filled with equal parts disappointment and relief.

After the war, Khokhlov tried to end his career as an intelligence officer, but he was strongly discouraged from retiring by his employers. He was trained for assignments that involved “the physical liquidation of our enemies.”12

This ate away at Khokhlov’s conscience. In 1954, he was tasked with the assassination of Georgiy Sergeyevich, leader of an anti-communist organization. Khokhlov showed up at his doorstep in West Germany and solemnly declared, “Georgiy Sergeyevich, I have come to you from Moscow. The Central Committee of the Communist Party of the Soviet Union has ordered your assassination. The murder is entrusted to my group. … I cannot let this murder happen.”13

Khokhlov immediately defected to the United States, where he promptly held a shocking press conference explaining who he was. At this presser, he showed off the weapon he’d been given to carry out the assassination: A fake cigarette case that could shoot tiny bullets laced with cyanide. It’s a little reminiscent of the umbrella gun we heard about three episodes ago.14

However, cyanide is a compound (or more technically a class of compounds) that incorporates a characteristic carbon-nitrogen bond. Thallium not included.

That’s because thallium was not one of the weapons in Khokhlov’s professional toolkit. Rather, he was the one who was dosed with thallium, by way of a cup of coffee someone else made for him. He didn’t even want the coffee, but this person, posing as a journalist, insisted. “You are too tired; drink it.” He had only a few sips before leaving, ignoring the other man’s protests that he should finish his coffee.15

Khokhlov was at the ballet when he started experiencing strange symptoms, like time appearing to stop. He was taken to the hospital, where his skin began to crack and his hair started to fall out. Eventually, doctors recognized what he was suffering from, and they performed an aggressive series of blood transfusions. It looked a little dicey for a minute, but the treatment actually worked. He made a full recovery and spent the next several decades teaching psychology at California State University.16 17

Thallium isn’t just for the professionals. There have been some amateur enthusiasts over the years, too, none more notable than Graham Frederick Young, also known as the Teacup Poisoner.

Young had been fascinated by poisons from childhood, when his father bought him a chemistry set. He spent so much time mixing various concoctions in flasks and tubes that he earned the nickname “The Mad Professor.”19

In 1970, doctors declared that Young had been cured of his murderous tendencies and recommended his release. He gleefully told a nurse that once he got out, he would kill one person for every year he had been kept at Broadmoor.

Despite this and everything else he had done, he was released the following February at the age of 23. He soon acquired a job at a photography supplies company. Less than four months later, his boss died from uncertain causes, and his coworkers were constantly falling ill. Stomach cramps, hair loss, and sexual dysfunction ran rampant through the town, killing at least one more person. Authorities looked for water contamination, chemical pollution, and even radioactive fallout, but ultimately chalked it up to an illness known as “the Bovingdon Bug.”

Apparently this was the cause of some irritation for Young. When the staff doctor insisted that all all health and safety measures were being strictly followed, he asked why no one had considered thallium poisoning, when it seemed so obvious.

Well, something was obvious, at least. Management quickly reported this strange behavior to the police, and Young was arrested only a few days later.

He gained instant notoriety in the press, much to his delight — although his moniker, “The Teacup Poisoner,” was much less impressive than he would’ve liked. He was found guilty on all charges and given four life sentences to serve at a maximum security prison on the Isle of Wight.

There he spent his time sporting a Hitler mustache and playing chess with another infamous killer, but this may not have been enough to hold his interest. Young died of a rather spontaneous heart attack at age 42. It seems plausible that the last life he took may have been his own, although no one investigated too closely. No one seemed terribly bothered that Graham Young was no more.

The Pale Horse was released the same year that Young began his spree, although he claimed to have never read it. This sounds believable enough. Considering the amount of literature he read on the subject of death by poison, he probably would have scoffed at the suggestion that he learned about thallium by reading popular fiction.20

If that is the case, then it would seem that Agatha Christie’s story may be responsible for more lives saved than lost. Anyone who has been inspired to imitate the fictitious assassin from The Pale Horse has certainly kept very quiet about it.

It is my sincere hope that by further promulgating information about this sinister substance, anyone listening will similarly only use this knowledge for good — if you ever have occasion to use it at all.

For a brief period of time, thallium was used as a depilatory agent — that is, something to cause hair loss. This could take the form of a barely sublethal oral dose of the metal, or as a cream to be applied directly to the face, or whatever other region the user wished to render bald. If you’re able to find a tube of that stuff, though, it’ll be a genuine antique — definitely not something you can find down at the corner drugstore.21

Hopefully you are at least aware of what you’re handling wherever you do find a sample of element 81. Twenty-five Russian soldiers at a weapons depot in Khabarovsk were not so lucky in 2004, when they uncovered a canister of thallium at a Cold War-era weapons depot. For reasons that we may never know, upon discovering the container full of unlabeled white powder, the soldiers immediately proceeded to sprinkle it on their feet, add it to their tobacco, and even snort it as though it were white powder of a different sort.22 23 24

No one is known to have died as a result, but they did get very sick. That year, they were honored with the title of At-Risk Survivors by the Darwin Awards.25

There are a few known antidotes to thallium poisoning. One of the most effective is the dye known as Prussian Blue. It’s often used as in paints — alongside Phthalo Blue, it was frequently one of the colors used by Bob Ross on his PBS show, The Joy Of Painting. Throwing back a dose of Prussian blue a few times a day for a few weeks on end is a reliable way to rid the body of thallium. It’s a little surprising, not only because pharmaceuticals are rarely found on canvas, but because Prussian blue is itself a fairly dangerous poison of the cyanide type. But you know what our old friend Paracelsus would have to say about that: “The dose makes the poison.”

The dose, in this case, needs to be measured quite precisely, so in the event of thallium poisoning, please consult a doctor before sucking down a tube of oil paint.

As mentioned at the beginning of the episode, there aren’t very many innocuous uses for thallium. Your best bet is to look for the right kind of specialty optical glass or photovoltaic cells from a solar panel. If you picked up a manganese nodule after episode 25, that rock might have a little thallium in it, too.

Of course, none of this will do for the discerning collector. For those of you who do pursue a pure sample of element 81, please exercise a great deal of caution when handling the material, wherever you manage to find it. And while you’re at it, make sure to clearly label your specimen as a highly toxic material for the benefit of any foolhardy folks who stumble upon your collection someday in the future.

Thanks for listening to The Episodic Table of Elements. Music is by Kai Engel. To learn why the CIA wanted to poison Fidel Castro with a dose of thallium, visit episodic table dot com slash T l.

Next time, we’ll plumb the depths of chemical knowledge with lead.

Until then, this is T. R. Appleton, reminding you that if someone admits a predilection for poisoning other people, it’s probably worth taking their confession at least a little seriously.


  1. Chemicool, Discovery Of Thallium. July 24, 2015.
  2. Nature Chemistry: In Your Element, Toxic Thallium. Anders Lennartson, last updated April 11, 2019.
  3. The Centers For Disease Control And Prevention, Thallium: Systemic Agent.
  4. The Naked Scientists, Chemistry In Its Element — Thallium.

    The body does eventually recognize thallium for the contaminant it is, and will carry it to the intestine for disposal. The problem is, once there, the body again thinks it looks like potassium and will re-absorb it.

    It didn’t take long after thallium’s discovery for people to learn about its toxic effects, and it was mostly used as a pesticide. The thing is, some people have a fairly loose definition of what constitutes a “pest.” And while it’s highly effective at exterminating annoyances with either six legs or four, it’s unmatched in its ability to dispose of two-legged animals.

    As a powder, thallium dissolves in water and is colorless, odorless, and tasteless. A quarter-teaspoon is more than enough to kill a person. The wide range of symptoms caused by thallium poisoning are easily confused for other, far more common afflictions, and those symptoms don’t set in until a day or two after the victim has ingested the poison — long enough for a would-be assassin to skip town.

    It’s hard to say how many people have died because of thallium. The victims of one prolific poisoner were incorrectly diagnosed as suffering from pneumonia, typhus, encephalitis, epilepsy, brain tumor, and alcoholic neuritis — and the record was only corrected because one doctor finally figured it out after the death of the seventh victim. Who knows how many killers exercised greater restraint and got away with it?4The Elements Of Murder: A History Of Poison, 321-364. John Emsley, 206.

  5. Slate, Blogging The Periodic Table: Thallium. Sam Kean, August 4, 2010.
  6. Minerals Yearbook, p. 1358. 1972.
  7. RadioTimes, The True Story Of How The Pale Horse Caught A Criminal And Saved Lives. Will Salmon, February 16, 2020.
  8. Flanders Health Blog, Thallium In The Human Body. Last updated December 17, 2020.
  9. The Royal Society Of Chemistry, Chemistry In Its Element: Thallium. Henry Nicholls.
  10. Time, How Agatha Christie Knew So Much About Poisons. Jennifer Latson, September 15, 2015.
  11. The Times Online, The Spy Poisoned By The KGB — But Who Lived To Tell The Tale. December 1, 2006.
  12. League Of Ukrainian Canadians, All Of Russia’s Enemies Have Lived In Fear Of The Assassin. March 12, 2018.
  13. The Spy Museum via The San Jose Mercury News, From Russia With Love: A History Of Poisonings. Thomas Boghardt, December 3, 2006.
  14. Mysterious Universe, A KGB Assassin, The CIA, And Strange Powers Of The Mind. Brent Swancer, September 20, 2019.
  15. Cafe, Ending In A Fall: America’s Response To The Poisoning Of Soviet Defector Nikolai Khokhlov. David Kurlander, September 3, 2020.
  16. Psychology Today, Inside The Mind Of A Poisoner Assassin. Raj Persaud and Peter Bruggen, March 9, 2018.
  17. The New York Daily News, Young Chemistry Whiz Graham Frederick Young Used His ‘Talents’ To Kill His Stepmother And Poison Other Family Members. Mara Bovsun, December 28, 2013. Who’s writing this incredibly long headlines?![/nonte]

    By age 13, people in Young’s orbit started getting mysteriously sick, from his classmates at school to his own family. Everyone chalked it up to a stomach bug — no one suspected they were being poisoned.

    Yet that’s exactly what was happening. Young was spiking his victims’ tea, first with antimony, but he quickly switched to the more lethal thallium. Indeed, it wasn’t very long before his stepmother collapsed in the garden and died.

    When Young’s father fell ill shortly after, another family member called the police. Young admitted everything he’d done, and at age 14, he became the youngest internee at the Broadmoor high-security psychiatric hospital.

    That didn’t slow him down, though. Only a few weeks after he was admitted to the hospital/prison, another patient/inmate died of cyanide poisoning. Young confessed that he had procured the poison by processing leaves from plants on the grounds, but no one believed him. Or maybe they didn’t want to believe him. Either way, the official story was that the man died by suicide.

    Suspicious things continued to happen during Young’s stay at Broadmoor. Staff and inmates alike contracted mysterious illnesses, and on one occasion, a communal teapot was found to be laced with a sodium-based toxin. All the while, he continued to read anything about poisons that he could get his hands on. Eventually, Young’s supervisors told him that his studies were likely to delay his release, so he became a little more surreptitious about them.18Biography.com, Graham Young. Last updated June 5, 2020.

  18. The Sun, Deadly Brew: How Agatha Christie’s The Pale Horse Inspired The Murders Of The Teacup Poisoner Who Killed Four And Poisoned His Family. Alison Maloney, February 17, 2020. Yes, despite the headline, this article suggests Young was not inspired by Agatha Christie.
  19. The Independent, The Poison Prescribed By Agatha Christie. John Emsley, July 19, 1992.
  20. BBC News, Toxic Metal Poisons Russia Troops. Last updated June 11, 2004.
  21. The Guardian, Thalium. GrrlScientist.
  22. BBC News, What Is Thallium? Last updated November 21, 2006.
  23. The Darwin Awards, 2004 At-Risk Survivor.

3 Replies to “81. Thallium: It Rides A Pale Horse”

  1. Is the discoverer is the same guy who invested the Cookes tube, leading to the CTR and the discovery of electrons?

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