MERCURY FROM MATERNAL SILVER TOOTH FILLINGS IN SHEEP AND HUMAN BREAST-MILK - A SOURCE OF NEONATAL EXPOSURE

Neonatal uptake of mercury (Hg) from milk was examined in a pregnant s heep model, where radioactive mercury (Hg-203)/silver tooth fillings ( amalgam) were newly placed. A crossover experimental design was used i n which lactating ewes nursed foster lambs. In a parallel study, the r elationship between dental history and breast milk concentration of Hg was also examined in 33 lactating women. Results from the animal stud ies showed that, during pregnancy, a primary fetal site of amalgam Hg concentration is the Liver, and, after delivery, the neonatal lamb kid ney receives additional amalgam Hg from mother's milk. In lactating wo men with aged amalgam fillings, increased Hg excretion in breast milk and urine correlated with the number of fillings or Hg vapor concentra tion levels in mouth air. It was concluded that Hg originating from ma ternal amalgam tooth fillings transfers across the placenta to the fet us, across the mammary gland into milk ingested by the newborn, and ul timately into neonatal body tissues. Comparisons are made to the U. S. minimal risk level recently established for adult Hg exposure. These findings suggest that placement and removal of ''silver'' tooth fillin gs in pregnant and lactating humans will subject the fetus and neonate to unnecessary risk of Hg exposure.