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

AX5-137
Table AX5-8.4 (cont’d). 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
100 ppm
(A) Exposure for 158 ±
2 days from 21 days
through 14 days of
lactation; (B)
Nonpregnant control
Group A; (C) Exposure
144 ± 2 days from day
21 up to delivery; (D)
Nonpregnant control
Group C; (E) Lactating
rats not exposed to Pb;
(F) Nonpregnant rats
not exposed to Pb.
In drinking water
Pb acetate
250 mg/mL
Beginning at 5 wks of
age, rats exposed to Pb
for 5 wks, followed by
no additional exposure.
In drinking water
Rat When dietary calcium was reduced from the normal 1 to 0.05%, bone calcium
concentration decreased by 15% and bone Pb concentration decreased by 30%
during the first 14 days of lactation. In nonlactating rats on the 0.05% calcium
diet, there were also decreases in bone calcium, but no incremental bone
resorption nor Pb efflux from bone, suggesting the efflux from bone during
lactation was related to bone resorption. Enhancement of calcium (2.5%) in
the diet of lactating rats increased calcium concentration in bone by 21%, but
did not decrease bone resorption, resulting in a 28% decrease in bone Pb
concentration and concomitant rise in systemic toxicity.
Rat Demonstrated adverse effects in rat offspring born to females whose exposure
to Pb ended well before pregnancy. Five wk-old-female rats given Pb acetate
in drinking water (250 mg/mL) for five wks, followed by a one mo period
without Pb exposure before mating. To test the influence of dietary calcium
on Pb absorption and accumulation, some pregnant rats were fed diets
deficient in calcium (0.1%) while others were maintained on a normal calcium
(0.5%) diet. All Pb-exposed dams and pups had elevated blood Pb levels;
however, pups born to dams fed the diet deficient in calcium during pregnancy
had higher blood and organ Pb concentrations compared to pups from dams
fed the normal diet. Pups born to Pb-exposed dams had lower mean birth
weights and birth lengths than pups born to non-Pb-exposed control dams
(p < 0.0001), even after confounders such as litter size, pup sex, and dam
weight gain were taken into account.
Concentration (µg/dL) in
whole blood at day 14 of
lactation or equivalent:
Group B = 26.1 ± 2.1,
Group A = 32.2 ± 2.7*;
Group D = 23.8 ± 2.1,
Group C = 28.2 ± 2.2*;
Groups E and F = 5.1 ±
0.4.
* p < 0.01, compared to
appropriate control
Blood Pb concentration of
pups (µM): Low
calcium/no Pb = 0.137 ±
0.030 C ; Low calcium/Pb =
1.160 ± 0.053 A ; Normal
calcium/No Pb = 0.032 ±
0.003 C ; Normal
calcium/Pb = 0.771 ±
0.056 B .
Values that are not
marked by the same letter
are significantly different
(p < 0.05).
Maldonado-Vega
et al. (2002)
Han et al. (2000)