Lead in breast milk and maternal bone turnover

Objective: Our purpose was to determine whether breast milk lead (Pb) levels are correlated with maternal blood Pb levels, bone loss, or bone turnover during reproduction. Study Design: Data were collected prospectively at 0, 1.5, 3, 6, and 12 months after delivery in 15 lactating and 30 bottle-feeding women. Variables included breast milk Pb (inductively coupled mass spectrometry), maternal blood Pb (atomic absorption spectrophotometry), osteocalcin (radioimmunoassay), and bone mineral density change (dual-energy x-ray absorptiometry). Results: Mean Pb breast milk concentrations were 6.1, 5.6, 5.9, and 4.3 ng/mL at the 1.5, 3, 6, and 12 months post partum, whereas mean maternal blood Pb concentrations were 1.4, 1.6, 1.7, and 1.4 μg/dL at 0, 3, 6, and 12 months post partum. The 5.6% bone loss and significant bone turnover were related to breast milk Pb levels but not to postpartum maternal blood Pb levels. Maternal and breast milk Pb values were modestly correlated at 1 to 2 months. Conclusions: Bone loss and bone turnover were related to breast milk Pb levels. In these women, there was no evidence that either high maternal blood or breast milk Pb concentrations are a major public health concern. (Am J Obstet Gynecol 2002;187:770-6.)