Check out this site - http://www.dmsa-chelation.info/

They found "DMSA was the most effective at removing mercury from the blood, liver, brain, spleen, lungs, large intestine, skeletal muscle, and bone. DMPS was more effective at removing mercury from the kidneys."

It states that DMPS does not cross the BBB and DMSA does ..

I read elsewhere that ALA does cross the BBB. That is probably why protocols supplement ALA with DMPS.

Kindest regards
D