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Lab Safety

Chemist who survived thallium poisoning speaks out

Thallium poisonings are infrequent, but medics need to know how to recognize them faster to help improve chances of recovery and find those responsible

by Andy Extance, special to C&EN
July 16, 2023 | A version of this story appeared in Volume 101, Issue 23


A British police van parked beside a brick house, with trees to the rear.
Credit: Luke O'Brien
Police thoroughly tested BM’s house in Southampton after he was diagnosed with thallium poisoning in September 2012.

The first sign that something was wrong was numbness in his feet. Then things got rapidly and severely worse. It was August 2012, and soon, a chemistry PhD student in the UK would be fighting for his life. The cause eventually became clear: thallium.

On Friday, Aug. 17, that PhD student was a tall, muscular man in his 20s working in the chemistry laboratories at the University of Southampton. He was unaware that his life would soon change catastrophically. This article will refer to him by the pseudonym BM to protect his privacy.

After a full day at the lab, BM headed home. It was there he first noticed something amiss. The bottoms of his feet had started to go numb. Yet, as an outgoing man with many friends, including those he’d gained as a university-level athlete, he was in demand on a Friday night. So BM went out to a local pub. He mentioned the numbness to friends but thought little of it.

That night, BM slept badly. He woke on Saturday to numbness rising above his ankles. In the shower, he was disturbed to feel the numbness rising up his legs.

There will be an interchange between what’s in your blood and what’s in your body water, and you’ll get the thallium distributed in all tissues of the body.
Atholl Johnston, forensic pharmacologist and toxicologist, Queen Mary University of London and St George’s, University of London, and science director, Analytical Services International

After calling the UK’s health advice and information service, NHS Direct, BM went to Southampton General Hospital. There, doctors were just as confused as BM, and they admitted him to conduct further tests. He wouldn’t leave the hospital for months.

Today, after a struggle lasting over a decade, BM has a somewhat normal life. Although he wishes to stay anonymous, he now wants to share his story. He wants to help raise awareness of the symptoms of thallium poisoning so that future victims won’t suffer an equally long delay until diagnosis and will have a better chance of identifying their poisoners. It’s very difficult to get thallium in the UK. Yet BM highlights that it can be less tightly controlled within chemistry departments than other poisons—such as mercury—that are less suited to malicious attacks. It’s time that this changed, he says.

Ominous signs

At about 9:00 p.m. on the Saturday he was admitted to Southampton General, BM’s knees collapsed as he was walking around the ward. The numbness had risen above them without him realizing it. An hour later, BM’s feet felt progressively more uncomfortable. Very soon, he was in excruciating pain. Even after he took morphine, he says, his feet felt as if they were being hit by “a red-hot hammer coated in needles.”

The next morning, BM’s housemate DC—also a pseudonym to protect BM’s privacy—visited him in the hospital, expecting a minor illness. “What we found instead was him curled up on a bed,” DC says. “I’ve never seen anyone in that amount of pain before. It was horrible. My girlfriend was in tears.”

Thallium hallmarks

Acute thallium poisoning can cause many symptoms.

Stomach: Diarrhea, nausea, and vomiting

Hands and feet: Pain and nerve damage

Head: Hair loss

Skin: Various problems, including acne-like symptoms and scaling on the palms and soles of the feet

Nails: White lines of discoloration known as Mees’ lines

Sources: Atholl Johnston; Hayley Willacy, “Thallium Poisoning,” Patient, last updated Oct. 27, 2021,; Br. J. Dermatol. 1998, DOI: 10.1046/j.1365-2133.1998.02083.x.

BM recalls, “At some points the entire surface of my skin felt like someone was blowtorching it, all the way up to the middle of my thighs.”

On Monday, Aug. 20, a neurologist diagnosed BM with Guillain-Barré syndrome, a disorder in which a person’s immune system attacks their nerves, and started treatment. It soon became clear that this was the wrong diagnosis. BM’s pain continued, and his mobility worsened such that by Friday he became unable to walk even with support. BM’s mother arrived from overseas on Sunday, Aug. 26. BM remembers almost nothing from the following 5 weeks. While he remained lucid and could answer simple queries during this time, he believes his mind didn’t record the period to block out the pain.

A key clue to the true cause of BM’s pain came during 2 weeks in late August and early September 2012, when his hair fell out.

His housemate DC recalls a visit to see BM on Sept. 11, when doctors asked DC to leave the room. “It was all very ominous,” DC remembers. “Before they let me back in, they gave me an apron, gloves, a face mask. Then I went back in, and he croaked to me, as his voice was almost gone, that they’d found out that it was thallium.”

From this point onward, things moved quickly. Within 12 h of blood tests confirming thallium’s presence, doctors sent him to a specialist poison unit at University Hospital Llandough on the outskirts of Cardiff, Wales. Meanwhile, the Southampton chemistry department shut down for detailed forensic tests. The police also went to BM’s house, extensively testing its contents and interviewing DC and BM’s three other housemates about the poisoning.

BM seemingly dodged the most common initial symptoms of high-dose thallium poisoning, which are diarrhea and vomiting. That’s according to Atholl Johnston, a forensic pharmacologist and toxicologist who works at Queen Mary University of London and St George’s, University of London. Johnston is also the science director at Analytical Services International, a London-based toxicology laboratory. Nerve damage starts to develop next, followed by the most distinctive symptom, hair loss. Thallium has been used to remove people’s hair “if they had a fungal infection like ringworm in their scalp,” Johnston says. Few people will have seen such a set of symptoms because, while there are some well-known thallium poisonings, such cases are “not very common at all,” Johnston says. But chemists are often the targets of the poisonings that do occur.

The secret to thallium’s toxicity is its ability to mimic a different and underappreciated element—potassium. We depend massively on potassium, Johnston says—for example, muscle power relies on potassium ions’ coordinated movement in and out of cells. A thallium ion is similar in size to a potassium ion, Johnston notes. “It substitutes for potassium, but it doesn’t do the same thing, so it stops the various bodily functions working,” he says. “That’s what causes the damage.”

BM’s resulting paralysis included his digestive system. Unable to absorb nutrition, his body instead digested itself. BM says he likely owes his survival to the size he’d developed doing sports to a high level. “I turned a quarter of my body weight into food,” BM recalls. “If I hadn’t had so much spare mass around my frame. . . to live off, I would have started to digest organs.”

In Cardiff, doctors treated BM by giving him Prussian blue (Fe7(CN)18), the only known antidote to thallium poisoning. Prussian blue has a very high affinity for singly charged metal ions like thallium, a feature that increases thallium’s elimination in feces. Gradually BM’s body started to work better, including his memory, which began to return around the beginning of October. While he needed to have what happened to him explained several times, today he vividly recalls the bright green poop that his revived digestive system had started producing.

In mid-October, doctors moved BM out of the specialist toxicology ward, and he realized that he was going to live despite the fact that his blood was still toxic enough that it should have killed him, he says. His nerve damage and muscle loss made movement extremely difficult. For example, he was unable to actively straighten his hands or feet. By early November, he returned to Southampton, to Western Community Hospital, for rehabilitative treatment lasting 5½ months.

The amount of thallium in BM’s blood finally returned to normal levels in December 2012.

No accident

While BM was in the hospital, the University of Southampton, the UK’s Health and Safety Executive (HSE), the Health Protection Agency, and county police conducted a joint investigation into the poisoning. They found no evidence of contamination at the university or an accident.

A scan of the first page of the occupational hygiene report.
Credit: UK Health and Safety Executive
The UK Health and Safety Executive found that workplace activities were not a credible source of the thallium exposure.

BM himself had never worked with the metal. The HSE concluded in January 2013 that “workplace activities do not present a credible source of exposure to thallium”.

The HSE report, obtained by C&EN under the UK Freedom of Information (FOI) Act, explores how someone might have obtained the thallium. It highlights that access to the lab building is secured by swipe cards and that extra security measures are taken outside normal work hours. While a secure chemical procurement system prevented private delivery of chemicals to the building, “not all thallium . . . is kept in locked cupboards,” the report notes. It would “not be feasible” to keep all sources of substances as toxic as thallium under lock and key, the report adds. That comment alludes to the small amounts used in most applications in chemistry departments, particularly experimental samples.

The most common use of thallium salts in a chemistry laboratory would be in synthesizing coordination complexes, according to inorganic chemist Andrew Weller of the University of York. But they are not commonly used for this today because of their toxicity. Silver salts work equally well in this context. “In my lab we haven’t used thallium salts in 15, 20 years,” he says.

Currently, the UK’s Control of Substances Hazardous to Health 2002 regulations don’t specify how different substances should be handled. Instead, they require risk assessments that minimize workplace exposure. Organizations take the precautions they deem appropriate.

At York, thallium salt reagents are carefully stored in locked poison cupboards, Weller says. Anyone wanting to use them must sign them out, record the amount they have used, and sign them back in again afterward. Research samples produced on a milligram scale probably wouldn’t be treated that way, Weller adds, but they would still be handled as toxic, with extreme care.

A key clue to how BM was poisoned comes from a set of lab reports that C&EN obtained through the FOI Act. They detail how the Health and Safety Laboratory in Buxton, England, tested various swabs taken from around the Southampton chemistry department. Inductively coupled plasma atomic emission spectroscopy data found that thallium was present in BM’s mug and on three laboratory surfaces.

On the morning of Aug. 17, BM had filled his mug from a thermos containing coffee made at home, just as he always did. “I didn’t wash it that day; I didn’t bother looking in it,” BM recalls.

Contamination would have been difficult to spot, Johnston says. He estimates that a lethal dose of a thallium salt would be just a sprinkling of a white powder, looking just like sugar. If thallium is swallowed, thallium ions would readily pass from your digestive system into your blood, Johnston explains. “There will be an interchange between what’s in your blood and what’s in your body water, and you’ll get the thallium distributed in all tissues of the body.”

Although doctors eventually solved the mystery of what was wrong with BM so that they could treat him, many questions remain unanswered. The most significant of them is, Who was responsible?

BM and his friends and family are adamant that he didn’t do this to himself, and BM points to police psychological assessments to support this assertion. Meanwhile, county police investigations were unsuccessful. “There are currently no lines of enquiry. However, with any unsolved case, this is subject to change should we ever receive new information in the future,” Detective Superintendent Justin Norris tells C&EN. “An offense remains undetected in this case, which means there is insufficient evidence to prove a crime has occurred.” Norris says he’d like to hear any further accounts of the case, including from new witnesses.

The best form of revenge

With the time limit for BM to be able to bring a civil legal case having passed and the police stumped, the chances of prosecuting his poisoner are nearly zero. Instead, he’s focusing on a different battle—getting his health back.

Despite the unusual cause of his nerve damage, BM received routine treatment, according to his doctor Caroline Hutchings, a consultant in rehabilitation medicine at Solent NHS Trust and University Hospital Southampton Foundation NHS Trust. “The effects on BM’s nerves cause very predictable consequences,” Hutchings says, speaking to C&EN with BM’s permission. “The signal that’s arriving from his feet to his brain doesn’t make sense to his brain. One of the few ways that the brain can make sense of it is that it hurts. People describe horrible pain.” Hutchings and her colleagues frequently have to help people with such pain after nerve damage, she says.

Hutchings and her colleagues treated the pain and restored most of the feeling to BM’s limbs. They also improved his mobility. By the time he left the hospital, he was using splints to keep his feet in place, crutches, and often a wheelchair.


On his release from the hospital, the university gave BM living accommodations adapted to his mobility needs. His rehabilitation owed a lot to his determination to get as much of his old life back as possible. When C&EN originally spoke to him in 2014, he said he wanted to “finish my PhD, get back to playing sport, and not have my splints and [not] use a wheelchair and crutches.”

Completing his PhD meant first deciding how to type his thesis. At the time, BM’s hands started to curl into fists when resting, so he often had to move them to reset them when typing. Eventually, he got “an old-style mechanical keyboard with spring-return keys on,” he says, which made typing easier.

By his graduation ceremony in 2016, BM was well enough to climb onstage in front of many of his chemistry department colleagues—just. “You hear my name called out,” BM recalls. “And there’s a very short, shocked silence of ‘Is he going to get up on the stage? Are they going to have to do some fancy trickery getting a wheelchair up there?’ And I kind of hauled myself up the stairs at the side of the stage. Then there’s this enormous round of applause from behind me. And I genuinely don’t know if any of the staff knew I was still alive. The raw volume of it is something I’ll remember for the rest of my life.

“I got someone to carry my crutches from one side of the stage to the other. . . . I was in splints. I could just about safely walk on a stable surface unsupported by anything.”

Even after he had earned his PhD, BM was far from the athlete he had once been. Initially, he tried to remain involved with sports. But now he says that his mobility hasn’t improved enough for him to participate. “It was making me miserable watching everyone else run around,” BM explains. “There’s always that niggling thought: ‘You could have been playing.’ And that really gets to me. So I don’t really want to, as a protection method for my mental health.”

BM’s attitude toward working closely with chemicals has changed in the opposite direction. It was something he didn’t want to do in the first years after being poisoned, but now it is something he does daily. In 2015, he told C&EN, “I don’t honestly think I’d be able to trust anyone in that kind of environment ever again.” Yet BM remained determined to get a job that used his chemistry qualifications, and in 2022 he finally managed to do so. He now works in hazardous waste management and is grateful for the support his employers and colleagues provide to accommodate his movement limitations.

Nevertheless, BM is still alarmed by the skull-and-crossbones symbols indicating toxic substances. “Anytime I see one of those, little hairs on the back of my neck stand up until I read the label and see that it’s not thallium,” he says.

BM is now relatively secure in his employment and life more broadly. He therefore wants to speak out to try to prevent others from being affected by thallium poisoning. For example, he hopes that if someone poisoned with thallium presents themselves to a doctor, his story will help them be diagnosed faster than he was. In his case, he feels the delay harmed the chances of finding out the truth of what happened and who was responsible. He also believes that the delay led to more nerve damage. A more rapid diagnosis might have given a better possibility that BM could walk without assistance, “maybe even run again,” and be employable sooner, he says. He has no problems with how the University of Southampton chemistry department treated him but would have preferred that the university overall speak more openly about his case. “I’m of the opinion that they would rather it remain buried or forgotten or underinvestigated,” BM says.

In an emailed response, a University of Southampton spokesperson says that it “cooperated fully with the extensive police and HSE investigations at the time, and no issues of workplace contamination were discovered.”

I’m of the opinion that they would rather it remain buried or forgotten or underinvestigated.
BM, survivor of thallium poisoning

BM also believes that health and safety standards should be tightened to require that thallium be locked up and treated with the highest levels of caution seen with other substances. BM would like the standard approach to be closely recording who has handled any thallium compounds, “to say that this person has taken this much out, like you have to do with mercury and radioactive compounds,” he says.

“An independent internal review carried out shortly after the incident found that the university had robust safe working practices, and clear procedures in place, relating to potentially hazardous materials,” the University of Southampton spokesperson says. “Our priority has always been the wellbeing and safety of our staff and students, and we therefore review all health and safety procedures on a regular basis.”

That internal review, which C&EN obtained under the UK FOI Act, found that some supervisors did not keep the most hazardous substances under lock and key. The review found no evidence that this led to any safety issues. It did, however, recommend that the Southampton chemistry department ensure consistency in locking up a list of substances including thallium.

“The University does not agree that errors were made by it in the first instance because none were found by the HSE or police,” the University of Southampton spokesperson comments by email.

C&EN first spoke to BM in 2014, such a long time ago that the author of this article offered BM a drink from his own water bottle with little thought about infectious diseases like COVID-19 or any other contamination. BM turned the offer down, later pointing out his increased sense of caution and decreased trust. Those feelings are worse, he says, because whoever is responsible is still out there.

“I don’t know why they did it; I don’t know if they’ll do it again to somebody else, and that’s kind of scary,” BM says. “I sometimes get upset and very angry about it. Then I remember that the best form of revenge is just overcoming it—to focus my rage towards that rather than something that I can’t have, which is justice.”

Andy Extance is a freelance writer based in Exeter, England.


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