Thallium is used in optical glass for transmission of long wavelength radiation, as an alloy with mercury in low temperature thermometers, and in the preparation of high density liquids. In many countries thallium salts are used as rodenticides.
Thallium compounds are highly toxic and being tasteless there are many accounts of their criminal use. Large doses cause acute gastrointestinal symptoms (pain, diarrhoea and vomiting) with neurological effects a few days later. Alopecia occurring 10-15 days post-ingestion is the most characteristic sign of thallium poisoning. Paraesthesia of the extremities can lead, in severe cases, to muscle paralysis and death from cardio-respiratory failure.
Laboratory Indices of Exposure
Exposure is usually monitored by measurement of thallium in urine but in severe poisoning episodes, blood, serum or plasma may also be taken for analysis.
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