A 29 year old female patient complains of decayed tooth. Patient is 7 months pregnant and gives history of cavity preparation and restoration with amalgam done with 16,17,26,27,37. Intra-oral examination reveals proximal caries with 26. The upper limit of urinary mercury in this patient is?​
1 microgm/L​
2 microgm/L​
3 microgm/L​
4 microgm/L​