Transport of Methylmercury and Inorganic Mercury to the Fetus and Breast-Fed Infant Karolin Ask Björnberg,1 Marie Vahter,1 Birgitta
Berglund,2 Boel Niklasson,3 Mats Blennow,2 and
Gunilla Sandborgh-Englund4 1Division of Metals and Health, Institute of Environmental Medicine,
Karolinska Institutet, Stockholm, Sweden; 2Division of Pediatrics
and 3Department of Obstetrics and Gynecology, Karolinska University
Hospital, Huddinge, Sweden; 4Division of Dental Biomaterials, Institute
of Odontology, Karolinska Institutet, Huddinge, Sweden Abstract It is well established that methylmercury (MeHg) and mercury vapor pass the placenta, but little is known about infant exposure via breast milk. We measured MeHg and inorganic mercury (I-Hg) in blood of Swedish mothers (n = 20) and their infants, as well as total mercury (T-Hg) in breast milk up to 13 weeks postpartum. Infant blood MeHg was highly associated with maternal blood MeHg at delivery, although more than twice as high. Infant MeHg decreased markedly until 13 weeks of age. Infant blood I-Hg was associated with, and about as high as, maternal blood I-Hg at delivery. Infant I-Hg decreased until 13 weeks. In breast milk, T-Hg decreased significantly from day 4 to 6 weeks after delivery but remained unchanged thereafter. At 13 weeks, T-Hg in breast milk was associated with infant MeHg but not with maternal MeHg. Conversely, T-Hg in breast milk was associated with maternal I-Hg but not with infant I-Hg. From the findings of the present study in which the exposure to both MeHg and I-Hg was low, we conclude that the exposure to both forms of mercury is higher before birth than during the breast-feeding period, and that MeHg seems to contribute more than I-Hg to infant exposure postnatally via breast milk. Key words: breast-feeding, breast milk, human, infant exposure, inorganic mercury, methylmercury, pregnancy. Environ Health Perspect 113: 1381-1385 (2005) . doi:10.1289/ehp.7856 available via http://dx.doi.org/ [Online 15 June 2005] Address correspondence to G. Sandborgh-Englund, Division of Dental Biomaterials, Institute of Odontology, Karolinska Institutet, Box 4064, SE-141 04 Huddinge, Sweden. Telephone: 46-8-524-881-03. Fax: 46-8-711-83-43. E-mail: gunilla.sandborgh@ofa.ki.se We express our gratitude to the participating women and to B. Palm for skillful laboratory assistance. We also acknowledge E. Berg for support with statistical analysis and J. Holmén for editing the manuscript. The study was performed by financial support from the Swedish Medical Research Council (grant 13450-02) . The authors declare they have no competing financial interests. Received 15 December 2004 ; accepted 14 June 2005. The full version of this article is available for free in HTML or PDF formats. |