PCDDs, PCdfs and Co-PCBs in human breast milk samples collected in Tokyo, Japan

To observe the distribution of PCDD/Fs and Co-PCBs in samples of human breast milk collected in Japan.

Using high-resolution gas chromatography, milk samples for polychlorinated dibenzo-p-dioxins (PCDDs; 14 congeners), polychlorinated dibenzofurans (PCDFs; 15 congeners) and coplanar polychlorinated biphenyls (Co-PCBs; 12 congeners) from 240 mothers residing in Tokyo were analysed. There were 120 donors each of primiparae and secundiparae, each group including 60 donors aged 25 to 29 y ("the younger group") and 60 aged 30 to 34 y ("the older group"). Individual milk samples (about 50 ml) were obtained 30 d after delivery in 1999 and in 2000.

The mean toxic equivalent (TEQ) level of PCDD/Fs (the sum of PCDDs and PCDFs) was 14.9 pg TEQ/g fat, of Co-PCBs 10.6 pg TEQ/g fat, and the total sum of PCDD/Fs and Co-PCBs was 25.6 pg TEQ/g fat. The mean TEQ levels of PCDD/Fs, Co-PCBs, and total PCDD/Fs and Co-PCBs were higher in primiparae than in secundiparae. In each of these, the levels were higher in the subgroup of older mothers. In the secundiparae, the mean levels were lower in the group of mothers who had breastfed their first babies than in those who bottle-fed or partly bottle-fed their first born.

The concentrations of PCDD/Fs and Co-PCBs in the breast milk of Japanese women were slightly lower than those described in previous studies conducted in Japan and other countries; and the concentrations of PCDD/Fs and Co-PCBs in the breast milk were influenced mainly by the mother's age and nursing history.