Concentrations of mercury, selenium and lead in blood samples from mothers and their newborn babies in four Greenlandic hunting districts

Abstract

Earlier investigations carried out in Greenland have shown high exposure levels of mercury and lead to be present. The levels of mercury and lead are found not to be of immediate risk to adults, but both elements are able to pass the placental barrier and thereby influence foetal development. As the foetus must be regarded as most sensitive to environmental toxicants it was found necessary to carry out a follow-up investigation in order to elucidate foetal exposure. This investigation was started in the fall of 1981 and continued until the end of 1982. Samples of venous blood were collected from women giving birth, and the foetal exposure was evaluated on the basis of samples of cord blood. Samples were taken at the local hospitals in the four districts of Upernavik, Umanak, Scoresbysund, and Angmagssalik. In total, 98 sample pairs were collected: 14 from Upernavik, 36 from Umanak, 17 from Scoresbysund, and 31 from Angmagssalik. At the time of sampling a questionnaire was filled out with information on the age of the mother, length of pregnancy, weight of child, smoking and eating habits of the mother. All samples were analysed for mercury and lead contents. Furthermore, the selenium concentration was analysed, as in animal experiments this trace element has been shown to alleviate toxic effects of mercury and probably of lead, too. The high exposure level of mercury in Greenland was confirmed in this study, too. A close correlation was found between the blood of mothers and children. The children's blood contains more mercury than that of the mothers, approximately 80% more. The highest concentration seen in a newborn baby was 177 μg/1, which is close to values found to have caused mercury intoxication during the Minamata episode in Japan. Selenium concentrations were found to be correlated between mothers and children, but in a non-linear way. The concentration level was found to exceed that of mercury on a molar basis. This might constitute a protective effect, and explain that neither in Greenland nor in other places where marine food is an important part of the total diet, has mercury intoxication been found, except in cases such as the Minamata area in Japan, where a local mercury pollution was present. Still, the high concentration in babies must give rise to concern. No correlation was found between mercury and selenium concentrations on an individual basis, neither in mothers nor in children. This indicates that the two elements pass the placental barrier independent of each other. As seen in other investigations, lead was also shown to pass the placental barrier, and a significant correlation was found between the blood of mothers and of children, the mean concentration being approximately the same. The mean concentration level in mothers was a little lower than should have been expected from earlier investigations. This is probably due to the fact that the blood lead level decreases during pregnancy. As shown in earlier studies from Greenland, the blood lead level was found to be on the same level as that found in European industrial areas. The present information on heavy metal exposure in Greenlandic hunting districts should be subjected to a closer evaluation as regards the influence on the health condition in the Greenlandic population now and in the future. Such material will he highly relevant to the understanding of the significance of the global pollution by heavy metals.