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Thallium

المؤلف:  Sue Jickells , Adam Negrusz (Editors)

المصدر:  Clarkes Analytical Forensic Toxicology

الجزء والصفحة:  109

2026-09-23

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Thallium

Most thallium compounds are colourless, taste less and odourless. The water-soluble salts of thallium include the sulfate, acetate and carbonate, all of which are highly toxic. Modern industrial uses of thallium salts include the manufacture of imitation jewellery and optical lenses, and in producing special alloys for seawater batteries. Thallium salts were also introduced as rodenticides and insecticides in the 1920s. Their use has been discontinued in many countries owing to their high toxicity, but they continue to be applied in some countries. The fatal oral dose of thallium in adults is less than 2 g.

The clinical picture of thallium poisoning is highly complex, and poisoning may be difficult to diagnose in its early stages. Initial signs and symptoms of acute thallium poisoning include fever, gastrointestinal upset and convulsions. Neurological symptoms may develop later and include both peripheral and central neurological changes. Cardiovascular changes, such as an increase in blood pressure and tachycardia, may develop after 1 to 2 weeks. The most character istic signs associated with thallium toxicity are dermatological changes, which may take up to 3 weeks to develop, and include an initial black pigmentation of the hair (visible under a micro scope) followed by loss of body hair, which can result in total alopecia. Nail growth may also be impaired with the development of white transverse lines, similar to those seen with arsenic poisoning. In particularly severe cases of thallium poisoning, extremely high levels of thallium in blood, plasma and urine may be recorded within the first few days after ingestion. Measurement of thallium excretion in urine is useful in cases for which oral antidotal therapy with Berlin (Prussian) blue (potassium ferric hexacyanoferrate) is instituted. This dye forms an insoluble complex with thallium in the gut, which leads to enhanced faecal excretion. Reference values for thallium in blood and urine are <1 μg/L. Concentrations in excess of 100 lg/L in blood and <200 μg/L in urine are associated with toxicity.