Dear of troy: You got the general idea about chelation. But it acts by sequestering the metal where it is no longer biologically active. The chelate compound may break down very slowly. I think the general idea is similar to way iron is in center of hemoglobin molecule. Haven't read about it for fifty years. I'll see if I can find a good URL about it.

It was late and I goofed.

http://www.hsph.harvard.edu/Organizations/DDIL/chelation.htm

Here is a very good URL. Very hard reading though. I'll give a handpainted medal to anybody who can read it and comprehend it. Other younger physicians excepted.