Air Quality Criteria for Lead Volume II of II - (NEPIS)(EPA) - US ...

AX172
Table AX6-6.1 (cont’d). Placental Transfer of Lead from Mother to Fetus
Reference and
Study Location Study Description Pb Measurement Findings, Interpretation
Europe (cont’d)
Barltrop (1969)
England
Latin America
Chuang et al. (2001)
Mexico City, Mexico
34 fetuses at gestational age 10 to 40 wks
obtained from termination of pregnancy and
neonatal deaths.
615 women recruited in 1994-1995.
Investigators used structural equation
modeling to estimate plasma Pb as the
unmeasured variable and to quantify the
interrelations of cord blood Pb with plasma
Pb, whole blood Pb, and bone Pb (cortical
and trabecular).
Blood Pb levels in femur, liver, blood, brain, heart,
and kidney measured.
Maternal whole blood Pb:
Mean 8.45 µg/dL (SD 3.94)
Maternal patella bone Pb:
Mean 14.24 µg/g bone mineral (SD 14.19)
Maternal tibia bone Pb:
Mean 9.67 µg/g bone mineral (SD 9.21)
Cord blood Pb:
Mean 6.55 µg/dL (SD 3.45)
Pb became detectable at gestational age 12 -14
wks. For skeletal (femur) and soft tissue with
high affinity (liver), Pb levels increased
progressively until term. In contrast, in soft
tissue with low affinity (heart), only a modest
increase in Pb levels was observed between 14
wks and term.
ln cord-ln maternal whole blood Pb:
Correlation coefficient = 0.82
ln cord-ln maternal plasma Pb:
Correlation coefficient = 0.89
ln cord-maternal patella Pb:
Correlation coefficient = 0.23
ln cord-maternal tibia Pb:
Correlation coefficient 0.18
The structural equation models indicated that
maternal plasma Pb had a stronger association
with fetal cord blood Pb compared to that of
whole blood Pb. In addition, the models
suggested a significant contribution of Pb from
the skeletal system to plasma during pregnancy,
a contribution that is independent of the
influence of maternal whole blood Pb.