Lead in Bone: Implications for Toxicology during Pregnancy and Lactation

Abstract

Advances in understanding the distribution and retention of lead in mineralized tissues are important for two reasons: first, bone lead may be a more accurate dosimeter of integrated absorption associated with chronic exposures, and second, bone lead may be a source of internal exposure to the host organism. Little attention has been paid to this second aspect, the remobilization of lead from bone. Mobilization of lead from bone is likely to occur during periods of altered mineral metabolism; since calciotropic factors determine the uptake and storage of lead in this compartment, changes in calcium-related regulatory factors are likely to affect lead compartmentation. Calcium metabolism changes drastically in humans during pregnancy and lactation; although relatively little is known of lead kinetics during these critical periods, it is likely that bone lead is mobilized and transferred to the more bioavailable compartment of the maternal circulation, with potential toxic effects on the fetus and the mother.

Lead Levels in the Breast Milk of Nursing Andean Mothers Living in a Lead-Contaminated Environment

“…These findings suggest that for the current group, maternal PbB level is a reasonably good predictor of PbM. Some studies showed an association between maternal age and PbM, suggesting that age may be a useful predictor of PbM (Silbergeld, 1991). However, the results of the present study found that there was no significant age effect on the PbM levels, indicating that Pb exposure was similar for younger and older nursing mothers in the Pb-contaminated study area.…”

Stress as a Potential Modifier of the Impact of Lead Levels on Blood Pressure: The Normative Aging Study

“…Many of the studies that used blood lead levels (which reflect mostly recent exposure) showed stable effect estimates but inconsistent associations with blood pressure (Hertz-Picciotto and Croft 1993; Staessen et al 1996); however, more recent studies that used bone lead levels [which reflect cumulative lead exposure and are assessed using K-shell X-ray florescence (KXRF) bone lead measurements] have shown more consistent associations with increased blood pressure and particularly with risk of hypertension (Cheng et al 2001; Glenn et al 2003; Hu et al 1996; Korrick et al 1999; Lee et al 2001; Martin et al 2006). Because approximately 95% of the lead in adults is stored in the bone, even with the significant decline in environmental lead exposure, the release from this bone store to blood and soft tissue can be an ongoing important source of exposure and toxicity, especially in older populations (Rabinowitz 1991; Silbergeld 1991; Silbergeld et al 1993; Tsaih et al 2001). …”

Determinants of bone and blood lead concentrations in the early postpartum period

“…As well as the risk posed by environmental exposure, concerns have been raised about fetal and neonatal exposure to maternal lead stores that may be released as bone is mobilised to meet the calcium demands of pregnancy and lactation 2. Data available from both animal models, and to a lesser extent from humans, indicate a rise in blood lead concentrations during pregnancy coincident with maternal bone demineralisation to meet increased fetal requirements 3…”