Maternal bone lead contribution to blood lead during and after pregnancy

We examined bone lead contribution to blood lead in a group of 311 immigran t women, 99% from Latin America, during the third trimester of pregnancy an d 1 to 2 months after delivery. We measured in vivo tibia and calcaneus (he el) bone lead concentration in the postdelivery period with K shell X-ray f luorescence. Prenatal and postnatal geometric mean (range) blood lead level was 2.2 mu g/dL (0.4 to 38.7) and 2.8 mu g/dL (0.4 to 25.4), reflecting lo w current exposure. Postnatal blood lead level was significantly higher tha n prenatal (P < 0.0001). Mean (range) tibia and calcaneus lead concentratio n was 6.7 mu g/g (-33.7 to 62.2) and 8.4 mu g/g (-30.1 to 66.4), reflecting varying but elevated past lead exposure. Mean calcaneus lead concentration was significantly higher than mean tibia lead concentration (P = 0.055). V ariance-weighted multiple regression and structural equation models showed that both calcaneus and tibia lead were directly associated with prenatal b lood lead but only calcaneus lead was associated with postnatal blood lead. Increasing natural log years in the United States independently predicted decreasing calcaneus and third-trimester blood lead. The data suggest that while some exogenous lead sources and modulators of blood lead level, such as use of lead-glazed pottery and calcium in the diet, control lead exposur e during and after pregnancy, endogenous lead sources from past exposure be fore immigration continue to influence blood lead levels in this sample. (C ) 2000 Academic Press.