Unfortunately, you will not find a "mercury free" person on this planet. No one will every get mercury free. Babies are born with mercury in their system. The normal reference range would have to be zero in that there is really no "safe" level of mercury. It's not meant to be stored in our bodies.

My husband did a EDTA & DMPS challenge 24 hour urine toxic metal test. His mercury was within the reference range. The first baseline test, showed that none of the heavy metals out of range. With the challenge, only one heavy metal was very elevated. That was lead. There was an increase in the mercury, but it still remained in the reference range. Even a heavy metal within the reference range can be problematic for an individual. That's why all of this so controversial.

I assume your doctor did a 24 hour urine baseline test to compare against the challenge.