The medical uses and commercial abuses of thallium

Thallium salts were once part of the medical pharmacopoeia, and used to remove hair. This unusual effect of thallium was discovered by accident in the 1890s when thallium was tested on tuberculosis patients as a cure for night sweats. It didn't stop them having them, but their hair fell out. Dr R. J. Sabourand, the chief dermatologist at the St Louis Hospital in Paris, reported this side effect in 1898; for a while he used it specifically to remove body hair from those with ringworm but gave up using it because it was too toxic. Its use was revived in the early 1920s at a recommended dose of 8 mg/kg bodyweight and it became the standard treatment for hair removal for 30 years, despite reports that around 40% of those given it experienced other side effects, generally very mild ones, although these were reported to disappear after three weeks. Another analysis of 500 patients, carried out by Drs Lourier and Zwitkis, was more reassuring in that no serious symptoms of thallium poisoning were observed although a quarter of those treated with it experienced pain in the legs and upset stomachs. (Once all the thallium has been excreted from the body, the hair will begin to grow again and return to its normal state.)

There seemed little cause for concern and thallium acetate was even regarded as sufficiently safe to be sold in over-the-counter products for removing unwanted hair. It was also used to remove unwanted relatives. It could be purchased as Celio cream or Koremlou cream and these became particularly popular in the 1930s. They contained 7% thallium acetate and a typical 10 g tube would contain 700 mg of the active agent.

The reaction to thallium varies markedly from person to person. A medical dose of 1200 mg of thallium acetate has proved fatal to some, yet others have survived self-administered doses of more than twice this amount. One 10-year-old boy died after eating only 200 mg of it. One individual who tried to kill herself by eating three tubes of Celio cream survived. Most of those who tried to kill themselves generally ate a single tube of this preparation, which should not have been enough to kill them, but for some it proved to be a fatal dose. Whether a would-be suicide or accidental victim of thallium poisoning survived depended primarily on thallium poisoning being recognized as such, and quickly. If it went undetected then even the most intensive care could not succeed in saving life because there was no antidote for the poison until the early 1970s.

Accidental overdoses of thallium acetate led to several fatalities in the 1920s and 1930s, and as a result thallium treatments were phased out and ceased being used after the 1950s. In one incident a group of boys in Budapest who had ringworm were given 5000 mg doses instead of 500 mg and they all died. The same thing happened at an orphanage in Granada, Spain, when 14 out of 16 children who were given overdoses died; in that case the cause was the pharmacist's faulty weighing scales. Of those who died, none showed loss of hair and of the two who survived, the hair loss did not begin until as late as a month after the thallium acetate had been taken.

Thallium sulphate was introduced as a pest control agent in the 1920s, and this too inevitably led to accidental deaths, suicides, and murders. Many members of an extended Mexican family were affected by eating tortillas made from a bag of Thalgrain, which had been stolen. Thalgrain consisted of barley coated with 1% of thallium sulphate and was used to kill squirrels. The women who had prepared the tortillas were suspicious of the grain because it was an unusual colour and appeared to be coated with something, but they decided to cook with it anyway. As a result, of the 31 people who were present at the event, 20 were taken ill and 6 died. Five died within two weeks but one member of the family lingered for a month before expiring.

A particularly large outbreak of thallium poisoning occurred in Guyana, South America, in the early 1980s when hundreds of people appear to have been affected, and 44 died. It all began when the Guyana Sugar Corporation imported 500 kg of thallium sulphate from Germany and used it to kill rats that were infesting their fields of sugar cane. For two years nothing untoward happened but then in 1983 doctors at St Joseph's Hospital in the Guyanese capital Georgetown began to treat people suffering from thallium poisoning. What started as a slow trickle of cases grew month by month until more than a hundred people needed treatment, and when a prominent Georgetown family reported sick then clearly something had to be done. By now there was widespread alarm as to the extent of the poisoning.

Tests on the milk which the family regularly drank revealed it was the source of the poison and checks at the farm from which they got their supply revealed sick cows suffering from thallium poisoning. They in their turn had been poisoned by eating molasses laced with thallium which had been used to deter farmers from letting their cattle wander into a nearby sugar plantation. Although the cows that ate the molasses were sickening, they continued to produce milk and this was sold to the general public. Some reports claimed that thousands of Guyanese people were affected by thallium but the US Centers for Disease Control, who were asked to investigate, found that many of the blood tests on those who thought they were suffering from thallium poisoning gave misleading results indicating levels of the metal that were totally incorrect.

Sometimes thallium has poisoned people, even to the extent of making their hair fall out, without the source of contamination being identified. More than 300 people living in the Ukrainian town of Chernovspy suffered this fate in 1989, and investigators discovered that the soil in the town was heavily polluted with the metal. The residents believed it had fallen in heavy rains, but a more likely explanation is that people in the town were using thallium compounds as home-made petrol additives to boost low-grade fuels.

There are still some uses of thallium in medical treatment even today but patients are not given anything approaching a toxic dose. The radioactive isotope thallium-201, which has a half-life of 73 hours, is used in the diagnosis of heart disease. This displaces some of the potassium in the heart muscle, but only if there is an adequate supply of blood to carry it there, and then the penetrating gamma rays that it emits can be monitored from outside the body. The patient is given an injection of the isotope and then scanned by a scintillation counter before and after physical exercise. The uptake of thallium-201 by the heart, and its distribution within the heart, will reveal the extent of the damage to that vital organ.

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