Chelation therapy is the standard treatment for any type of heavy metal poisoning and radiation sickness where it is suspected the radioactive material is still in the body. It uses chemicals that bind to metal ions in order to turn them into inert compounds that can be disposed of in the urine and feces.
Heavy metals poison the body by interfering with regular bodily functions through a chemical process. Passing the metal ions through the liver and kidneys, which usually process waste, merely results in the destruction of those tissues as well, resulting in the metal ions actually being concentrated in those areas.
Chelation uses chemicals which chemically combine with metals, creating inert compounds that will not interact with living tissue (much in the same way as the dangerous metal sodium combines with the dangerous gas chlorine to form salt, only the compounds are much more complicated in this case). These chemicals are also used in industrial processes for the same purpose, often to separate precious metals. DMSA is the most common chelating agent, and each chelating agent has a different chemical affinity for different heavy metals.
Chelation therapy is usually very safe. The chelation agents themselves will not interact with human tissues. Depending on the location of the heavy metal, they can be given intravenously, with an intramuscular injection, or orally.