No abstract

BackgroundLittle is known about the rates of loss (depuration) of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) from mothers during lactation. Depuration rates affect infant exposure to chemicals during breast-feeding, and fetal and lactational transfers during subsequent pregnancies.ObjectiveOur objective in this study was to estimate depuration rates of PBDEs and PCBs using serial samples of breast milk.MethodNine first-time mothers (primiparae) each collected samples at 4, 6, 8, 12, 16, 20, and 24 weeks after birth. Nine additional primiparae each collected two samples at varying time intervals (18 to > 85 weeks after birth). Analytical precision was assessed to evaluate the accuracy of measured monthly percentage declines in PBDEs and PCBs.ResultsThe four major PBDE congeners decreased 2 or 3% ± 1% per month over the 6-month period. These decreases were consistent over a 50-fold range (21–1,330 ng/g lipid weight) of initial PBDE concentrations in breast milk. The change in PCB-153 ranged from + 0.3% to –0.6% per month, with heterogeneous slopes and greater intraindividual variability. PBDE and PCB concentrations declined 1% per month over longer periods (up to 136 weeks).ConclusionsOur data indicate that PBDEs and PCBs are not substantially (4–18%) reduced in primiparae after 6 months of breast-feeding. Consequently, the fetal and lactational exposures for a second child may not be markedly lower than those for the first. Participants were volunteers from a larger study population (n = 82), and were typical in their PBDE/PCB levels and in many demographic and lifestyle factors. These similarities suggest that our results may have broader applicability.

Breast milk samples collected during 2003-2005 from 82 first-time mothers in 24 communities located throughout California contained levels of polybrominated diphenyl ethers (∑(tri-hexa (8))PBDEs; median = 53.3 ng/g lw, range = 9.60-1291) and polychlorinated biphenyls (∑(12)PCBs; median = 73.4 ng/g lw, range = 22.2-433) that are among the highest in the world. PBDE levels varied 100-fold. BDE-47 was the dominant PBDE congener, with levels exceeding the U.S.EPA Reference Dose (RfD) for neurodevelopmental toxicity (100 ng/kg/day) in most (60%) breast milk samples. In some samples, BDE-209 (2/82) and/or BDE-153 (5/82) were the dominant congeners, suggesting that BDE-209 can transfer to breast milk and/or break down in the mother and transfer to the nursing infant as the lower-brominated PBDEs associated with adverse effects. PBDE levels in California breast milk are approaching those of PCBs, and the trend PBDEs > PCBs may continue as PBDEs migrate from products to the indoor and outdoor environments.

Categorization is complete and characterization is well underway. Samples FSC-11-3-1 (NSR-F-270409-01) and FSC-11-3-2 (NSR-F-270409-02) are depleted uranium powders of moderate purity (~71-80 % U). Both were depleted to ~0.41-0.44% 235 U. Both samples have easily detectable amounts of 236 U, as well as 232 U at low levels. Samples FSC-11-3-1 and FSC-11-3-2 appear to be tails from an enrichment facility that used reprocessed U as part of its feed-stock. The U isotopic compositions of the two samples, while similar, differ outside of analytical uncertainty, suggesting that these samples came from different lots of material. Sample FSC-11-3-3 is indistinguishable from a natural uranium ore concentrate (~78% U) of moderate purity. Two anomalous objects (11-3-1-4 and 11-3-2-5) were found in the material during aliquoting, but have not been further analyzed.