title: Transport of methylmercury and inorganic mercury to the fetus and breast-fed infant.
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.
authors.affiliation: Division of Metals and Health, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Karolin Ask
authors.initials: KA
authors.lastname: Björnberg
authors.forename: Marie
authors.initials: M
authors.lastname: Vahter
authors.forename: Birgitta
authors.initials: B
authors.lastname: Berglund
authors.forename: Boel
authors.initials: B
authors.lastname: Niklasson
authors.forename: Mats
authors.initials: M
authors.lastname: Blennow
authors.forename: Gunilla
authors.initials: G
authors.lastname: Sandborgh-Englund
mesh_terms: D000328:Adult; D001942:Breast Feeding; D005260:Female; D005333:Fetus / Q000378:metabolism*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007287:Inorganic Chemicals / Q000097:blood / Q000493:pharmacokinetics; D008431:Maternal-Fetal Exchange; D008628:Mercury / Q000097:blood / Q000493:pharmacokinetics*; D008767:Methylmercury Compounds / Q000097:blood / Q000493:pharmacokinetics*; D011247:Pregnancy
chemical_list: D007287:Inorganic Chemicals; D008767:Methylmercury Compounds; D008628:Mercury