Individual characteristics associated with PBDE levels in U.S. human milk samples

Background: Reported polybrominated diphenyl ether (PBDE) concentrations in human samples in the United States have been higher than in Europe and Asia. Little is known about factors that contribute to individual variability in body burden. Objective: In this large study we measured PBDE concentrations in human milk from the United States during 2004-2006. We assessed characteristics associated with concentrations in milk and change in milk concentration between 3 and 12 months postpartum. Methods: We analyzed 303 milk samples obtained 3 months postpartum for PBDEs. A second sample was analyzed for 83 women still lactating 12 months postpartum. PBDE concentrations in milk and variability by individual characteristics such as age, parity, and prepregnancy body mass index (BMI) were evaluated using generalized linear models. Results: PBDE congeners BDEs 28, 47, 99, 100, and 153 were detected in > 70% of samples. BDE-47 concentrations were the highest, ranging from below the limit of detection to 1,430 ng/g lipid, with a median of 28 ng/g lipid. Concentrations of most individual PBDE congeners and the sum of BDEs 28, 47, 99, 100, and 153 (ΣPBDE) were lower among mothers > 34 years of age compared with those 25-29 years of age and higher among mothers with high compared with normal BMI, after adjustment for other covariates. Parity was not associated with PBDE concentration. The change in ΣPBDE concentration in milk between 3 and 12 months postpartum was highly variable (median increase, 14%; interquartile range, -26% to 50%). Conclusions: PBDEs were detected in nearly all human milk samples, varying by maternal weight and age and over the course of breast-feeding.