Concentration of mercury in hair of indigenous mothers and infants from the Amazon basin.

Hair mercury concentration, as an indicator of mercury body load, was studied in 251 samples of indigenous women and children living in selected areas of the Amazonian region. The mothers or women of child-bearing age, either non-Indians or Indians, and their children were sampled along the Madeira River and in the Kayapó reservation (Fresco River), respectively. Among the sampled individuals there were mothers with infants less than 2 years old. Total mercury in hair was determined by cold vapor atomic absorption spectrometry after alkaline digestion. The distribution of hair mercury concentration greater than 10 microg/g occurred in 67.4% of non-Indian women and 25% of Indian women; overall only 1% of non-Indian women had concentrations of hair mercury above 50 microg/g. In women of child-bearing age, the median and range of hair mercury concentration was 14.08 microg/g, and 0.8-94.7 microg/g for non-Indians, and 8.30 microg/g, and 0.8-13.3 microg/g for Indians. The correlation between maternal hair mercury and mercury in hair of infants (less than 2 years of age) still breast-feeding, was statistically significant only for non-Indians (r = 0.555 p < 0. 001). The correlation between length of breast-feeding and mercury concentration in infant's hair was significant for Indian children (r = 0.512; p = 0.029) but not for non-Indian children (r = 0.025; p = 0.832). A subsampling of 30 mothers had segmented hair analysis that showed a mean decrease of 20% in body burden during pregnancy, thus indicating the extent of placental transference of mercury to fetuses.