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To assess the efficacy of the bans in reducing PBDE levels, we recruited 67 California first time mothers (sampled during 2009-2012) and collected cord blood at birth (n = 31), breast milk (n = 66) and maternal blood (n = 65) at 3-8 weeks postpartum. Using the same sample extraction procedures and analytical instrumentation method (GC-HRMS), we compared PBDE as well as PCB levels in these breast milk samples to those from our previous study (n = 82, sampled during 2003-2005) and found that the sum of PBDEs over the ∼7 year course declined by 39% (GeoMean = 67.8 ng/g lipid in 2003-2005; 41.5 ng/g lipid in 2009-2012) and that the sum of PCBs declined by 36% (GeoMean = 71.6 ng/g lipid in 2003-2005; 45.7 ng/g lipid in 2009-2012). This supports our earlier finding of a PBDE decline (39%) in blood. We also found that the PBDE concentrations and congener profiles were similar in breast milk and their matched maternal/cord blood: BDE-47 was the dominant congener, followed by BDE-153, -99, and -100. Similar levels and congener profiles of PBDEs in these matrices suggest that they are at equilibrium. Therefore, we propose that maternal serum levels may be used to predict an infant's daily dose of PBDE exposure from breastfeeding when breast milk levels are not available. In addition, our study confirmed that breastfeeding babies are still exposed to high levels of PBDEs, even though PBDE levels are decreasing., (Copyright © 2015 Elsevier Ltd. All rights reserved.)