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

AX5-136
Table AX5-8.4. Bone Lead as a Potential Source of Toxicity in Altered Metabolic Conditions
Compound
Dose/Concentration
Duration Exposure
Route Species Effects Blood Level Reference
Pb acetate
200 µg/mL
105 days prior to mating
or 105 days prior to
mating and during
gestation and lactation
(160 days)
In drinking water
Pb acetate
12 mM
8 wks prior to mating
and during gestation
In drinking water
Pb acetate
100 ppm
(A) Exposure for 158 ±
2 days from 21 days of
age to midlactation; (B)
Exposure 144 ± 2 days
from day 21 up to
delivery; (C) Exposure
only during lactation;
(D, E, and F) groups of
nonpregnant rats
exposed for periods
equivalent to groups A,
B and C, respectively.
In drinking water
Mice Results suggested very little Pb was transferred from mother to fetus during
gestation, however, Pb transferred in milk and retained by the pups accounted
for 3% of the maternal body burden of those mice exposed to Pb prior to
mating only. The amount of Pb retained in these pups exceeded that retained
in the mothers, suggesting lactation effectively transfers Pb burden from
mother to suckling offspring. Transfer of Pb from mothers was significantly
higher when Pb was supplied continuously in drinking water, rather than
terminated prior to mating.
Rat Considerably higher lactational transfer of Pb from rat dams compared to
placental transfer was reported. Continuous exposure of rat dams to Pb until
day 15 of lactation resulted in milk Pb levels 2.5 times higher than in whole
blood, while termination of maternal Pb exposure at parturition yielded
equivalent blood and milk levels of Pb, principally from Pb mobilized from
maternal bone.
Rat In rats exposed to Pb 144 days prior to lactation (B), the process of lactation
itself elevated blood Pb and decreased bone Pb, indicating mobilization of Pb
from bone as there was no external source of Pb during the lactation process.
Rats exposed to Pb for 158 days (A)(144 days prior to lactation and 14 days
during lactation) also experienced elevated blood Pb levels and loss of Pb from
bone. Pb exposure only during the 14 days of lactation was found to
significantly increase intestinal absorption and deposition (17 fold increase) of
Pb into bone compared to nonpregnant rats, suggesting enhanced absorption of
Pb takes place during lactation. The highest concentration of Pb in bone was
found in nonpregnant, nonlactating control animals, with significantly
decreased bone Pb in lactating rats secondary to bone mobilization and transfer
via milk to suckling offspring.
Not given Keller and Doherty
(1980)
Concentration (µg/l) in
whole blood at day 15 of
lactation:
Controls = 14 ± 4; Pbexposed
until parturition =
320 ± 55; Pb-exposed
until day 15 of lactation =
1260 ± 171*
*p < 0.001 compared with
dams at parturition.
Concentration (µg/dL) in
whole blood at day 14 of
lactation or equivalent:
Group A = 31.2 ± 1.1;
Group B = 28.0 ± 1.7;
Group D = 27.3 ± 2.2;
Group E = 24.7 ± 1.2
Palminger Hallén
et al. (1996)
Maldonado-Vega
et al. (1996)