INDEPTH: ENVIRONMENT
Thallium
CBC News | May 18, 2004
Thallium is a rare metallic element, similar in its properties and colour to aluminum. The metal develops a bluish tarnish when exposed to the air, and is so soft it can be cut with a knife.
The chemical found in the Teck Cominco smelter is thallium sulphate, a odourless, tasteless, colourless compound that dissolves in water. It was used as rat poison and insecticide before the practice was banned in the 1970s.
Thallium compounds are currently used in electronic equipment such as solar cells, infrared light detectors and medical imaging devices. It is also produced as a byproduct of coal burning and lead smelting, as well as in cement factories.
When it enters the environment, it doesn’t break down and is absorbed by plants. The thallium then enters the food chain and can accumulate in fish and shellfish.
Most people are exposed to very low levels of thallium in their food. Cigarette smoke also contains low levels of the metal.
At higher concentrations, found mainly in industrial settings, thallium is highly toxic and can cause nerve, kidney and liver damage. The metal can be inhaled as dust or can enter the body through the skin.
Some workers who were exposed daily to thallium dust have developed numbness in the fingers and toes. Higher doses can cause digestive problems, hair loss, and even death. Thallium is also a suspected carcinogen, although no studies have shown conclusively that it does cause cancer.
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