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

AX4-28
Reference, Study
Location, and
Period Study Description
Mexico (cont’d)
Téllez-Rojo et al.
(2004)
Mexico City
1997-99
Table AX4-7 (cont’d). Bone Lead Studies in Pregnant and Lactating Subjects
Tested the hypotheses that
maternal bone Pb burden is
associated with increasing
maternal whole PbB and plasma
Pb over the 3 trimesters of
pregnancy and that this association
is modified by rates of maternal
bone resorption. Urine was
analyzed for cross-linked Ntelopeptides
(NTx) of type I
collagen, a biomarker of bone
resorption. Patella and tibia Pb at
1 mo postpartum. Mixed models.
Lead Measurement (SD or range)
PbB in µg/dL, Bone Pb in µg/g Bone Mineral Findings, Interpretation
Participants (n = 193):
PbB (µg/dL): initial 7.10 (±1.72), 1st trimester 6.47 (± 0.17), 2nd
trimester5.80 (± 0.17), 3rd trimester 6.05 (± 0.17).
Plasma (µg/L): 1st trimester 0.13 (±1.88), 2nd trimester 0.12 (± 1.95), 3rd
trimester 0.12 (± 1.88) (geometric means and SD)
Bone Pb during pregnancy:
Tibia 11.35 (±8.82, adjusted for negative values), patella 13.82 (±10.97,
adjusted for negative values).
Nonparticipants (n = 134):
PbB 6.82 (±1.75), tibia 13.71 (±9.17, adjusted for negative values), patella
11.79 (±9.75, adjusted for negative values).
Found an increasing trend for plasma Pb among women with the highest
bone Pb ($median level of 12.1 µg/g) but a decreasing trend among lessexposed
women(below the median level). The observed increase reached its
maximum among women with both the highest bone Pb and the highest
bone resorption. In comparison with women with a low bone Pb and a high
NTx level, those with a high bone Pb and a high NTx level had, on average,
an 80% higher mean plasma Pb. In the cross-sectional analyses for each
trimester of pregnancy, there was an increasingly stronger association
between bone Pb and plasma Pb (log-transformed) as pregnancy progressed.
An increase in patella lead of 10 µg/g would be associated with 9% (p =
0.07), 24% (p < 0.01), and 25% (p < 0.01) increases in plasma Pb in the 1st,
2nd, and 3rd trimesters of pregnancy, respectively. The corresponding
values for tibia lead were 8% (p = 0.16), 19% (p < 0.01), and 13% (p =
0.01), respectively. Dietary calcium intake was inversely associated with
plasma lead.
They concluded that the results
support the hypothesis of a
biologic interaction between
bone Pb burden and bone
resorption. They also suggest
that as pregnancy progresses,
bone Pb may be mobilized
increasingly into plasma.