Accumulation characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans and polychlorinated biphenyls in human breast milk from a seaside city of North China

Breast milk samples were collected from 51 mothers in a seaside city Dalian, where the residents usually have higher dietary exposure to polychlorinated dibenzo- p -dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) due to the larger consumption of seafood. The lipid-basis concentrations of ∑Cl 2–8 DD/Fs, ∑Cl 2–10 Bs, and total toxicity equivalent (WHO-TEQ) were measured to be in the ranges of 35.7–2727.8 pg/g, 4.91–52.64 ng/g, and 2.27–36.30 pg/g, respectively. The average proportion of ∑Cl 2–3 DD/Fs was higher than that of ∑Cl 4–7 DD/Fs in the collected human breast milk samples, suggesting that the health risk of Cl 2–3 DD/Fs should be especially concerned. The concentration data of PCDD/Fs and PCBs in human breast milk essentially followed a positive skew probability distribution. Women in high-level exposure scenarios exhibited a higher potential to accumulate homologues Cl 4 DFs, Cl 7 DFs, Cl 8 DF, and Cl 6 Bs in breast milk. Three PCDD/F congeners (1,2,3,6,7,8-Cl 6 DF, 1,2,3,4,7,8-Cl 6 DF, and 1,2,3,4,6,7,8-Cl 7 DD) and three PCB congeners (PCB 126, PCB 138, and PCB 169) were identified as good indicators for the accumulation of PCDD/Fs and PCBs in human breast milk, respectively. The food-to-milk accumulation factors (FMAF) were calculated to evaluate the accumulation potentials of different PCDD/F and PCB congeners in human breast milk via dietary exposure. The calculated FMAF value presented a non-monotonic variation with the logarithm of n -octanol–water partition coefficient (log K OW ) with a peak at a log K OW value of about 7.3 and a valley at a log K OW value of about 8. The mean value of the estimated daily intake (EDI) of total WHO-TEQ for breast-fed infants in Dalian, predicted by Monte Carlo simulation, was 10 folds higher than the upper range of the tolerable daily intake (TDI) value (4 pg WHO-TEQ/kg bw/d), suggesting continued and enhanced efforts should be made to reduce the exposure risk of infants to PCDD/Fs and PCBs. • Cl 8 DD and Cl 4–7 Bs are the dominant homologues in human breast milk. • Average proportion of ∑Cl 2–3 DD/Fs was higher than that of ∑Cl 4–7 DD/Fs. • Calculated FMAF value presented a non-monotonic variation with log K OW value. • Predicted EDI mean of WHO-TEQ for breast-fed infants was 40.0 pg/kg bw/d.