Thallium is a heavy metal used in electronics, optical equipment, and in chemical research. It was previously used as a rodenticide, and is more toxic to humans than mercury, lead, cadmium, or copper.
Thallium has a half life from 3 to 8 days, and is excreted in both urine and feces. The majority of thallium’s toxic properties are due to its chemical similarity to potassium. Thallium disturbs the sodium potassium balance, and at high enough dose is lethal. Thallium poisoning is relatively rare, but has been noted in some populations with the most common presentation being diffuse muscle point, joint pain, and alopecia. 
Common symptoms of acute thallium poisoning include:
- Home grown fruits and green vegetables produced in areas adjacent to thallium releasing industry may contain thallium. Thallium is readily absorbed through plant roots.
- Water near hazardous waste sites has been shown to have elevated levels of thallium, as was the surrounding soil.
- Thallium is released by coal fire power plants, cement factories, and smelting operations, and can then deposit onto nearby soil and plants. This process is a common source of thallium exposoure.
- Individuals working in industries associated with thallium release regularly have higher levels of thallium due to deposition of thallium on their skin.
- Smokers have been shown to have twice as much thallium in their bodies when compared to non-smokers.
- Urinary Testing
- Urinary excretion of thallium may be used to investigate clearance and possible toxicity.
- Blood Chemistry
- Other Testing
- Electroretinography and electromyography, which are used to measure membrane instability and decreases in distal motor units, may be helpful in identifying thallium toxicity.
- Chelation therapy is not recommended to increase thallium clearance as the thallium complexes formed are highly lipophilic and my increase thallium levels in the brain.
- Other Therapy
- Therapy is focused on increasing fecal and urinary excretion. Sodium iodide can be used to bind to thallium and decrease absorption.
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- Shannon MW (2007) Shannon: Haddad and Winchester’s Clinical Management of Poisoning and Drug Overdose, 4th ed Chap 73 Lead Saunders.
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- Brockhaus A, Dolgner R, Ewers U, Kramer U, Soddemann H, Wiegand H (1981) Intake and health effects of thallium among a population living in the vicinity of a cement plant emitting thallium containing dust. Int Arch Occup Environ Health 48(4):375-89
- Agency for Toxic Substances and Disease Registry (ATSDR). 1992 Toxicological profile for thallium. Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service.