Facts About Thallium Poisoning

Medical Author: Melissa Conrad Stöppler, MD
Medical Editor: William C. Shiel Jr., MD, FACP, FACR

The March 2007 poisoning of an American woman and her daughter in Russia with the element thallium sparked widespread media attention. After the women became ill in Moscow, they returned to the U.S. for treatment, where the diagnosis of thallium poisoning was confirmed.

Thallium is a soft, malleable gray metal that was previously widely used in rat poisons and insecticides. Thallium itself and compounds containing the element are highly toxic. It is particularly dangerous because compounds containing thallium are colorless, odorless, and tasteless. Because of this high toxicity, the World Health Organization (WHO) recommends against the use of thallium in rodent and insect poisons. However, poisons containing thallium are still in use in some parts of the world.

Small amounts of thallium are normally found in the earth's crust and atmosphere. It is also present in small amounts in cigarette smoke. Thallium has multiple industrial uses, and certain isotopes of thallium are used in medical imaging studies. Thallium can be absorbed from the skin as well as be ingested or inhaled. If a significant amount (significant poisoning is usually defined as ingesting over 1 gram of thallium, or over 8 milligrams per kilogram of body weight) of thallium enters the body, symptoms of thallium poisoning develop.

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