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

AX4-27
Reference, Study
Location, and
Period Study Description
Mexico (cont’d)
Hernandez-Avila
et al. (2002)
Mexico City
1994
Hernandez-Avila
et al. (2003)
Mexico City
1994-95
Table AX4-7 (cont’d). Bone Lead Studies in Pregnant and Lactating Subjects
Evaluated the effects that maternal
bone Pb has on anthropometry at
birth in 223 mother-infant pairs.
Anthropometric data (birth length,
head circumference) collected
within the first 12 hr following
delivery. Maternal information
was obtained 1 mo postpartum.
Transformed anthropometric
measurements to an ordinal 5category
scale, ordinal logisticregression
models.
Tested the hypothesis that in a
randomized trial of lactating
women a dietary calcium
supplement will lower PbB levels.
Lactating women (mean age 24 yr)
were randomly assigned to receive
either calcium carbonate (1200 mg
of elemental calcium daily) or
placebo in a double-blind trial.
Blood samples were obtained at
baseline, and 3 and 6 mo after the
trial began. Primary endpoint was
change in maternal PbB in relation
to supplement use and other
covariates with multivariate
generalized linear models for
longitudinal observations.
Lead Measurement (SD or range)
PbB in µg/dL, Bone Pb in µg/g Bone Mineral Findings, Interpretation
Participants (n = 223) Cord blood 7.01 (±3.5), maternal PbB 8.82 (±4.0),
tibia 9.83 (±8.9), patella 14.14 (±13.0).
Nonparticipants (n = 494): Cord blood 6.75 (±3.50), PbB 8.47 (±4.19).
Birth length of newborns decreased as tibia Pb levels increased. Compared
with women in the lower quintiles of the distribution of tibia Pb, those in the
upper quintile had a 79% increase in risk of having a lower birth length
newborn (odds ratio 1.79; 95% CI: 1.10, 3.22). The effect was attenuated–
but nonetheless significant- even after adjustment for birth weight. Patella
Pb was positively and significantly related to the risk of a low head
circumference score; this score remained unaffected by inclusion of birth
weight.
Lactating calcium group (n = 296): PbB 9.2 (±4.2), tibia 10.7 (±9.8), patella
16.2 (±15.7)
Lactating placebo (n = 321): PbB 9.4 (± 5.0), tibia 9.6 (±10.3), patella 13.5
(± 15.1)
Women randomized to the calcium supplements experienced a small decline
in PbB of 0.29 µg/dL (95% CI: !0.85, !0.26). The effect was more
apparent among women who were compliant with supplement use and had
high patella Pb of $5 µg/g. Among this subgroup, supplement use was
associated with an estimated reduction in mean PbB of 1.16 µg/dL
(95% CI: !2.08, !0.23), an overall reduction of 16.4%.
The authors estimated the
increased risk of having a low
head-circumference score to be
1.02/ µg Pb/g bone mineral (95%
CI: 1.01, 1.04). Odds ratios did
not vary substantially after the
authors adjusted for birth weight
and other important determinants
of head circumference.
Among lactating women with
relatively high Pb burden,
calcium supplementation was
associated with a modest
reduction in PbB levels.