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 Sigma Cl2-8DD/Fs, Sigma 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 Sigma Cl2-3DD/Fs was higher than that of Sigma Cl4-7DD/Fs in the collected human breast milk samples, suggesting that the health risk of Cl2-3DD/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, Cl8DF, and Cl(6)Bs in breast milk. Three PCDD/F congeners (1,2,3,6,7,8-Cl6DF, 1,2,3,4,7,8-Cl6DF, and 1,2,3,4,6,7,8-Cl7DD) 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/kgbw/d), suggesting continued and enhanced efforts should be made to reduce the exposure risk of infants to PCDD/Fs and PCBs.

Automated summary

This study collected breast milk samples from 51 mothers in Dalian, China, and found that they had higher exposure to polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) due to their higher consumption of seafood. The study also observed differences in the accumulation potentials of different PCDD/F and PCB congeners in breast milk and highlighted the higher exposure risk of infants to these chemicals.