INFERTILITY, BIRTH DEFECTS, AND FETAL DEVELOPMENTAL EFFECTS RELATED TO MERCURY FROM DENTAL FILLINGS VII

Based on animal studies using rats, sheep, and monkeys as well as human studies, mercury from amalgam in the blood of pregnant women crosses the placenta and appears in amniotic fluid and fetal blood, liver, and pituitary gland within 2 days of placement [10,14,15, 34-36,43-47,60,/54]. Studies have found a significant correlation between number of amalgam fillings of the mother and the level of mercury in the fetus, infants, and young children[10,14,15,34-40], and also with the level in mother's milk [10,38-42]. Breast milk has been found to increase the bioavailability of inorganic mercury, which was found to be excreted to milk from blood at a higher level than organic mercury(41,44,61). The main mechanism of transfer was found to be binding to albumin(45). For non-occupationally exposed populations and populations without high fish consumption, these studies found dental amalgams appear to be the main source of mercury in breast milk and the fetus, but significant levels of methyl mercury are also often found in breast milk [43,44,46,54,61]. U.S. ATSDR staff[62] indicate that under normal circumstances mercury in mother's milk should be under 1.7 ug/L, and 3.5 ug/L appears to be an adequate screening level for health risk. They indicate that there is evidence that contaminated breast milk is a source of potential risk to infants. An Italian study indicates that a commonly used mercury tolerance level for human milk is 4 ppb(43).Mercury is often stored in breast milk and the fetus at much higher levels than that in the mother [10,36,38-46,60,61/54]. Milk from mothers with 7 or more fillings was found to have levels of mercury approximately 10 times that of amalgam free mothers. The milk sampled ranged from 0.2 to 57 ug/L. In a population of German women, the concentration of mercury in early breast milk ranged from 0.2 to 20.3 ug/L. After 2 months laction the level had declined and was 0.1 to 11.7 ug/L[64]. A Japanese study found that the average mercury level in samples tested increased 60% between 1980 and 1990[47]. The level of mercury in umbilical cord blood, meconium, and placenta is usually higher than that in mother's blood[43- 47].Meconium(first stool) level appears to be the most reliable indicator of fetal mercury exposure and often has significant levels when there are low levels in mother's blood and cord blood(46c). The level of maternal blood or hair mercury is significantly correlated with mercury level in meconium and in nursing infants , so maternal tests can be easily used as a screen for developmental dangers[43-47,127]. But fetal levels can be significant when there are low levels in maternal blood(46c).