Transplacental transfer of cobalt: Evidence from a study of mothers and their neonates in the African Copperbelt

Abstract

Background: Transfer of the trace metal cobalt (Co) from mother to foetus has not been documented in pop-ulations with high environmental exposure to Co, as is the case in the African Copperbelt mining region. We analysed data obtained from 246 mother-infant pairs included (at delivery) in a previously published case -control study on birth defects, done in Lubumbashi (Democratic Republic of Congo) between March 1, 2013, and Feb 28, 2015.Methods: Co was measured by Inductively Coupled Plasma Mass Spectrometry in maternal blood, maternal urine, umbilical cord blood and placental tissue, as available.Results: The Co concentrations [geometric mean (GM) with interquartile range (IQR)] in maternal blood (GM 1.77 mu g/L, IQR 1.07-2.93) and urine (GM 7.42 mu g/g creatinine, IQR 4.41-11.0) were highly correlated (Spearman r = 0.71, n = 166; p < 0.001) and considerably higher than reference values determined for general populations elsewhere in the world. The concentrations of Co in umbilical cord blood (GM 2.41 mu g/L) were higher (Wilcoxon test, p < 0.001) than in maternal blood (GM 1.37 mu g/L), with a correlation between both values (Spearman r = 0.34; n = 127, p < 0.001). Co concentrations in placental tissue (geometric mean 0.02 mu g/g wet weight) correlated with concentrations in maternal blood (Spearman r = 0.50, n = 86, p < 0.001) and in neonatal blood (Spearman r = 0.23, n = 83, p = 0.039).Conclusion: This first study of maternal and neonatal Co concentrations in the African Copperbelt provides strong evidence of a high transfer of Co from mother to foetus.