Inorganic mercury and methylmercury in placentas of Swedish women.

Abstract

We determined levels of inorganic mercury (I-Hg) and methylmercury in placentas from 119 Swedish women, not selected with respect to high exposure of mercury. Our objective was to relate placental Hg species with maternal and fetal blood concentrations and to evaluate possible associations with selenium. We performed the analyses using automated alkaline solubilization/reduction and cold-vapor atomic fluorescence spectrophotometry. I-Hg levels in placenta increased with an increasing number of maternal dental amalgam fillings (p < 0.001). Despite placental accumulation (median, 1.3 microg/kg; range, 0.18-6.7 microg/kg wet weight), a substantial fraction of maternal blood I-Hg, probably as Hg(0), reached the fetus. Although MeHg transferred easily to the fetus, it also accumulated in the placenta. On average, 60% of placental Hg was in the form of MeHg. The median concentration was 1.8 microg/kg (range, 0-6.2 microg/kg wet weight), more than twice the maternal blood concentration. We found significant associations between MeHg and selenium in both maternal and umbilical cord blood but not in the placenta. The associations were particularly obvious in freshwater fish consumers, probably reflecting that fish is a source of both MeHg and selenium. We found no correlations between I-Hg and selenium. This study increases the understanding of Hg, in its different forms, in human placenta and how they are related to maternal and fetal exposure.

Influence of prenatal exposure to environmental pollutants on human cord blood levels of glutamate

“…The lack of a significant association for Hg and glutamate or aspartate levels could be due to the fact that the highest levels of T-Hg found in the samples (66 µg/L ≡ 0.33 µM) are lower than the concentrations of methylmercury that significantly inhibit [ 3 H]-aspartate uptake (IC20 value: 2.1 µM). It should be noticed that mercury levels in umbilical cord blood and placenta are positively correlated (Kozikowska et al, 2013;Ask et al, 2002). We also found that PCB 138 and β-HCH inhibited glutamate transport in human placentas with high affinity (~ 10 nM) but low efficacy (~ 50 % of maximum inhibition).…”

Blood dynamics of mercury and selenium in northern elephant seals during the lactation period

“…This high Hg transfer during gestation raises the question of how Hg exposure affects the offspring during its most sensitive period of development. The main form of Hg transferred through the placenta, MeHg (Ask et al, 2002;Wagemann et al, 1988), can affect the normal neuronal development and the immune system of offspring (National Research Council, 2000), potentially having consequences to future growth and fitness.…”

The placenta as a barrier for toxic and essential elements in paired maternal and cord blood samples of South African delivering women

“…35,26 Speciation of mercury in maternal and cord blood and placentas by Ask et al show that methyl mercury species concentrations are higher in the umbilical cord blood than in maternal blood, and the methyl mercury concentrations in placentas are twice of those in maternal blood, indicating retention of methyl mercury in placenta tissue. 36 The majority of studies associates elevated concentrations of mercury with consumption of contaminated fish and marine products. 37 In our study, dietary intake of fish was found to be low.…”