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Detecting toxic thallium exposure
Thallium is a by-product of lead smelting. The clinical interest in thallium derives primarily from its use as a rodenticide since this is the most frequent route of human exposure.
Thallium is rapidly absorbed via ingestion, inhalation, skin contact, and through the mucous membranes of the mouth, gastrointestinal tract, and lungs. It is considered to be as toxic as lead and mercury, with similar sites of action.
The mechanism of action of thallium is:
-Competition with potassium at cell receptors to affect ion pumps
-Inhibition of DNA synthesis
-Binds to sulfhydryl groups on proteins in neural axons
-Concentrates in renal tubular cells and reacts with protein to cause necrosis
Patients exposed to high doses of thallium (>1 g) present with alopecia (hair loss), peripheral neuropathy and seizures, and renal failure.
Reference values apply to all ages.
Normal blood concentrations are <1 ng/mL.
Significant exposure is associated with thallium in blood >10 ng/mL, and blood concentrations as high as 50 ng/mL. The long-term sequelae from such an exposure is poor.
High concentrations of gadolinium and iodine are known to interfere with most metals tests. If either gadolinium- or iodine-containing contrast media has been administered, a specimen should not be collected for 96 hours.
1. Pelcloval D, Urbanl, P, Ridsonl P, et al: Two-year follow-up of two patients after severe thallium intoxication. Hum Exper Toxicol 2009;28:263-272
2. Zhao G, Ding M, Zhang B, et al: Clinical manifestations and management of acute thallium poisoning. Eur Neurol 2008;60:292-297