i do not see limitations in mercury testing. i guess maybe i look at the positive side of it. if a person has mercury poisoning, drs and scientists will find a way to test for it, no matter what obstacles they have to overcome. the patient just has to learn what those tests are so they can ask for them if they want them. it is all a matter of picking the tests that work and using others that work somewhat, to cooberate findings, and eliminating the ones that don't work, or don't work well.