Mercury in the Umbilical Cord: Implications for Risk Assessment for Minamata Disease.

Abstract

Umbilical cord tissue was obtained from 50 births in the Faroe Islands, where high mercury intake is due to ingestion of pilot whale meat. The mercury concentration correlated significantly with the frequency of maternal whale meat dinners during pregnancy and with mercury concentrations in umbilical cord blood and in maternal hair. The results were compared with published values for mercury in umbilical cord tissue from 12 infants diagnosed with congenital methylmercury poisoning in Minamata, Japan. From the regression coefficients obtained in the Faroese samples, the median umbilical cord mercury concentration of 4.95 nmol/g dry weight in Minamata would correspond to 668 nmol/l cord blood and 114 nmol/g maternal hair. These levels agree well with other evidence of susceptibility of the fetus to increased exposure to methylmercury.ImagesFigure 1.Figure 2.

Effects of methylmercury on neurodevelopment in Japanese children in relation to the Madeiran study

“…Also, it has been demonstrated that the mercury concentration in the umbilical cord tissue was well associated with the mercury concentration in cord blood (r s =0.85), rather than that in maternal hair (r s =0.77) (Dalga˚rd et al 1994). On the other hand, Japanese maternal hair mercury levels in this study could explain only 18% of the variation of prenatal exposure (r s =0.42).…”

Assessment of Intrauterine Methylmercury Exposure Affecting Child Development: Messages from the Newborn

“…Given the conversion equation developed by Akagi et al (1998), i.e., [Maternal-hair T-Hg concentration at parturition (μ g/g)] = 25.24 × [MeHg concentration in dry cord tissue (μ g/g)], the maximum value (i.e., 0.37 μ g/g) of MeHg concentration in dry cord tissue as shown in Table 3 was estimated to be 9.3 μ g/g of maternal-hair T-Hg concentration, which would be near the critical concentration of MeHg affecting the nervous system function asymptomatically (National Research Council 2000;Murata and Dakeishi 2005). In the Faroese birth cohort study, while T-Hg concentrations in cord blood and in maternal hair at parturition (range, 0.2 ~ 39.1 μ g/g) TABLE TABLE T were employed for the risk assessment of MeHg neurotoxicity (Grandjean et al 1997(Grandjean et al , 2001Sørensen et al 1999;Murata et al 1999bMurata et al , 2004aDebes et al 2006), the exposure assessment was made using the freeze-dry umbilical cord in addition to the former two samples (Dalgård et al 1994;Grandjean et al 2005).…”

“…After reading the article, Dr. Robert W. Miller of the U.S. National Cancer Institute (1976) submitted a short letter entitled "Dried human umbilical cords and study of pollutant" to the Lancet and gave the two researchers full marks for the usefulness of dry umbilical cord, describing that cords systematically collected and stored might be used as a biological dosimeter for changes in the levels of pollutants over time. Since then, mercury concentrations in cord blood and tissue, which are part of the fetus, have been employed as fetal biomarkers of hazardous substances (Dalgård et al 1994;Grandjean et al 1997;Nakai et al 2004).…”

Subclinical effects of prenatal methylmercury exposure on cardiac autonomic function in Japanese children

“…Also, it has been suggested that a myth that hair mercury concentration reflects the methylmercury concentration circulating in the blood may collapse if a study population includes subjects with artificial hairwaving . The mercury level in the umbilical cord tissue has been reported to be associated well with that in cord blood (Dalga˚rd et al 1994), and most Japanese families treasure a small piece of the umbilical cord of the child as a birth memento (Akagi et al 1998). For this reason, we tried to collect dry umbilical cord samples of the children from parents who participated in our study.…”