Mercury in blood samples was speciated from mothers and their infants up to
2 mo after delivery. There were significant correlations between umbilical
cord blood and maternal blood for methylmercury (MeHg) and inorganic mercu
ry (I-Hg) levels. The MeHg levels in cord blood were significantly higher t
han in maternal blood, while I-Hg levels were about the same. The maternal
MeHg and I-Hg levels remained stable during the sampling period, whereas th
e MeHg concentration in infant blood decreased more than 45% between the 72
-h and 2 mo sampling times. The I-Hg levels in infant blood were low at bir
th, and remained low during the sampling period. The results of the present
study do not support I-Hg absorption through milk as a significant source
of exposure. However, the number of observations is small, and a larger stu
dy is warranted in order to verify the data.