of cement factories, coal-burning power plants, and metal sewers. The main source of elevated thallium concentrations in water is the leaching of thallium from ore processing operations. See also Myocardial perfusion imaging Citations General bibliography External links Thallium at The Periodic Table of Videos (University of Nottingham) Toxicity, thallium NLM hazardous substances databank – Thallium, elemental ATSDR – ToxFAQs CDC – NIOSH Pocket Guide to Chemical Hazards Chemical elements Post-transition metals 1861 introductions 1861 in science Chemical elements with hexagonal close-packed structure