| Inorganic Mercury and Methylmercury in Placentas of Swedish Women Karolin Ask, Agneta Åkesson, Marika Berglund, and Marie Vahter Division of Metals and Health, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden 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 µg/kg ; range, 0.18-6.7 µg/kg wet weight) , a substantial fraction of maternal blood I-Hg, probably as Hg0, 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 µg/kg (range, 0-6.2 µg/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. Key words: fetal exposure, human, inorganic mercury, methylmercury, placenta, pregnancy, selenium. Environ Health Perspect 110:523-526 (2002) . [Online 3 April 2002] http://ehpnet1.niehs.nih.gov/docs/2002/110p523-526ask/ abstract.html Address correspondence to M. Vahter, Division of Metals and Health, Institute of Environmental Medicine, Karolinska Institutet, Box 210, S-171 77, Stockholm, Sweden. Telephone: +46 8 728 75 40. Fax: +46 8 33 70 39. E-mail: Marie.Vahter@imm.ki.se We express our gratitude to the participating women, the midwives at the Karolinska Hospital, K. Bremme, K. Osman, B. Palm, and A. Schütz. We acknowledge U. Björs for skillful analytical assistance. The study was performed with financial support from the Environment Protection Agency, Stockholm, Sweden. Received 17 May 2001 ; accepted 13 November 2001.
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