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

Abstract

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 (SigmaPBDE) 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 SigmaPBDE 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.

Figure 1

PBDE congener concentrations stratified by age (x-axis; years) and adjusted for parity, prepregnancy BMI, and race. Numbers above the bars are means; error bars indicate 95% confidence intervals. Sample sizes for each age group: 32 for < 25 years, 88 for 25–29 years, 130 for 30–34 years, and 54 for ≥ 35 years. *p < 0.05 in generalized linear model comparing with reference group (25–29 years).

Figure 2

PBDE congener concentrations stratified by prepregnancy BMI (x-axis) and adjusted for age, parity, and race. Numbers above the bars are means; error bars indicate 95% confidence intervals. Sample sizes for each BMI group: 52 for low (< 19.8 kg/m²), 189 for normal (19.8 to ≤ 26.0 kg/m²), 27 for overweight (> 26.0 to ≤ 29.0 kg/m²), and 36 for obese (> 29.0 kg/m²). *p < 0.05 in generalized linear model compared with reference group (normal).

Figure 3

Percent change in PBDE concentration in milk between 3 and 12 months postpartum. Squares represent median; small horizontal bars represent the 25th and 75th percentiles; and vertical bars display the spread of the data between the 5th and 95th percentiles. *p < 0.05 for the sign test, testing the null hypothesis that the median percent change equals zero.

Figure 4

Percent change in estimated maternal PBDE body burden between 3 and 12 months postpartum, calculated as concentration (ng/g lipid) × body weight (kg) × body fat percentage (μg). Squares represent median percent change; small horizontal bars represent the 25th and 75th percentiles; and vertical bars display the spread of the data between the 5th and 95th percentiles.