Longitudinal Hair Mercury Concentration in Riverside Mothers along the Upper Madeira River (Brazil)

Mercury releases from gold mining occurred during the 1980s in the Upper Madeira river, a Southern tributary of the Amazon. Downstream from these areas, riverside residents rely on fish consumption for subsistence. In July of 1993, hair samples were collected for mercury analysis from a group of mothers and their infants and one pregnant woman. By assuming a constant rate of hair growth (1.1 cm per month), a temporal profile of the methylmercury exposure was determined for the previous 2 to 3 years. The length of hair segments corresponded to hair growth during pregnancy and the subsequent breastfeeding periods. During all periods, hair mercury concentrations in six mothers were in the range of 4.5–26.8 ppm, slightly lower than those of their infants (8.2–28.4 ppm). Further segmental analyses of hair mercury from another six mothers showed concentrations in the range of 12.2–41.0 ppm during the three trimesters of pregnancy and 4.0–33.5 ppm during breast feeding—slightly lower than their infants (11.6–50.4 ppm). Another four mothers showed hair mercury concentrations in the range of 21.3–84.4 ppm.