Abstract

Thallium and its compounds are often highly toxic. Contact with skin is dangerous, and adequate ventilation should be provided when melting this metal. Many thallium(I) compounds are highly soluble in water and are readily absorbed through the skin. Exposure to them should not exceed 0.1 mg per m of skin in an 8-hour time-weighted average (40-hour work week). Thallium is a suspected human carcinogen.

Part of the reason for thallium's high toxicity is that, when present in aqueous solution as the univalent thallium(I) ion (Tl), it exhibits some similarities with essential alkali metal cations, particularly potassium (due to similar ionic radii). It can thus enter the body via potassium uptake pathways. Other aspects of thallium's chemistry differ strongly from that of the alkali metals, such as its high affinity for sulfur ligands. Thus, this substitution disrupts many cellular processes (for instance, thallium may attack sulfur-containing proteins such as cysteine residues and ferredoxins). Thallium's toxicity has led to its use (now discontinued in many countries) as a rat and ant poison.

Among the distinctive effects of thallium poisoning are hair loss (which led to its initial use as a depilatory before its toxicity was properly appreciated) and damage to peripheral nerves (victims may experience a sensation of walking on hot coals), although the loss of hair only generally occurs in low doses; in high doses the thallium kills before this can take effect. Thallium was once an effective murder weapon before its effects became understood and an antidote (Prussian blue) discovered. Indeed, thallium poisoning has been called the "poisoner's poison" since thallium is colorless, odorless and tasteless; its slow-acting, painful and wide-ranging symptoms are often suggestive of a host of other illnesses and conditions.

Treatment and internal decontamination

There are two main methods of removing both radioactive and stable isotopes of thallium from humans. First known was to use Prussian blue, which is a solid ion exchange material, which absorbs thallium. Up to 20 g per day of Prussian blue is fed by mouth to the person, and it passes through their digestive system and comes out in the stool. Hemodialysis and hemoperfusion are also used to remove thallium from the blood serum. At later stage of the treatment additional potassium is used to mobilize thallium from the tissue.

Bioconcentration

According to the United States Environmental Protection Agency (EPA), thallium release to the environment was reported in Texas and Ohio. This may indicate bioconcentration in aquatic ecosystems.

Thallium compounds

The odorless and tasteless thallium sulfate was also used as rat poison and ant killer. Since 1975, this use in the United States and many other countries is prohibited due to safety concerns.

Detection in body fluids

Thallium may be quantitated in blood or urine as a diagnostic tool in clinical poisoning situations or to aid in the medicolegal investigation of suspicious deaths. Normal background blood and urine concentrations in healthy persons are usually less than 1 μg/litre, but they are often in the 1–10 mg/litre range in survivors of acute intoxication.

Famous uses as a poison

There are numerous recorded cases of fatal thallium poisoning. Because of its use for murder, thallium has gained the nicknames "The Poisoner's Poison" and "Inheritance Powder" (alongside arsenic).

Famous uses as a poison | Australia's "Thallium Craze"

In Australia, in the early 1950s, there was a notable spate of cases of murder or attempted murder by thallium poisoning. At this time, due to the chronic rat infestation problems in overcrowded inner-city suburbs (notably in Sydney), and thallium's effectiveness as a rat poison, it was still readily available over the counter in New South Wales, where thallium sulphate was marketed as a commercial rat bait, under the brand "Thall-rat".

- In September 1952, Yvonne Gladys Fletcher, a housewife and mother of two from the inner Sydney suburb of Newtown, was charged and tried for the murders of both her first husband, Desmond Butler (who died in 1948) and her abusive second husband, Bertrand "Bluey" Fletcher, a rat bait layer, from whom Yvonne had obtained the thallium poison that she used to kill him earlier that year. Suspicions were raised after it became obvious to friends and neighbours that Bluey Fletcher was suffering from the same fatal illness that had killed Yvonne's first husband. A police investigation led to the exhumation and testing of Desmond Butler's remains, which showed clear evidence of thallium, and this led to Yvonne being convicted of Butler's murder. She was sentenced to death, but this was subsequently commuted to life imprisonment after the NSW Government abolished the death penalty; she was eventually released in 1964. At the time of the trial, it was reported that this was the first known case in Australia of a person being convicted of murder by administering thallium. The Fletcher case is also notable for the fact that one of the arresting officers was Sydney detective Fred Krahe, who later became notorious for his suspected close involvement with elements of Sydney's organised crime scene and his alleged involvement in the disappearance of social activist Juanita Nielsen.

- A month later, in October 1952, Bathurst grandmother Ruby Norton was tried for the murder of her daughter's fiancė Allen Williams, who died of thallium poisoning at Cowra Hospital in July 1952. Despite allegations that Norton hated all the men in her family and Williams was an unwanted son-in-law, Norton was acquitted.

- In 1953, Sydney woman Veronica Monty, 45, was tried for the attempted murder of her son-in-law, noted Balmain and Australian rugby league player Bob Lulham, who was treated for thallium poisoning in 1952. After separating from her husband, Monty had moved in with her daughter Judy and Judy's husband, Bob Lulham. The sensational trial revealed that Lulham and Monty had an "intimate relationship" while Lulham's wife was at Sunday mass. Monty was found not guilty; Judy Lulham divorced her husband as a result of the revelations about his affair, and Veronica Monty killed herself with thallium in 1955.

- In July 1953, Sydney woman Beryl Hague was tried for "maliciously administering thallium and endangering her husband's life". Hague confessed to buying Thall-rat from a corner shop and putting it in her husband's tea, because she wanted to "give him a headache to repay the many headaches he had given me" in violent disputes

- In 1953, Australian Caroline Grills was sentenced to life in prison after three family members and a close family friend died. Authorities found thallium in tea that she had given to two additional family members. Grills spent the rest of her life in Sydney's Long Bay Gaol, where fellow inmates dubbed her "Aunt Thally".

The Australian TV documentary "Recipe for Murder", released in 2011, examined three of the most sensational and widely reported Australian thallium poisonings, the Fletcher, Monty and Grills cases.