Test Details: Thallium is excreted in the urine and can be found within an hour after exposure and be detected as long as two months after exposure. Thus, Urinary thallium levels may reflect recent or chronic exposure and the presence of thallium in urine after acute exposure may persist for up to several weeks. After severe thallium poisoning reported symptoms have varying times of onset and include gastroenteritis, multi-organ failure and neurologic injury.