Thallium Poisoning from Eating Contaminated Cake — Iraq, 2008. cdc.gov.usa. September 19, 2008. Thallium is an odorless, tasteless, heavy metal formerly used in rodenticides and still used in some manufacturing processes (e.g., electronics, pharmaceuticals, and glass). Thallium also has been used for intentional poisonings . Acute thallium poisoning produces gastrointestinal symptoms and signs, such as vomiting and acute abdominal pain, in the first few hours after ingestion, and initially is indistinguishable from other causes of acute gastrointestinal toxicity. [ See ]. See also: CDC: Thallium caused death in four in Iraq.