PBDEs In Breast Milk, Bioavailability Of PBDEs And The Associated Human Health Risk Assessment

Polybrominated diphenyl ethers(PBDEs) are a class of typical persistentorganic pollutants(POPs), which can cause adverse effects on the ecosystem andhumans. Thus, they are of great concerned. Breast milk is the single most natural,safy and complete natural food to infant. Therefore, the monitoring of PBDEs inbreast milk provides a good indicator of PBDE exposure from the environment andthe food chain, especially for mothers and their nursing infants. Bioavailability was akey parameter used in the human health risk assessment of environmental pollutants.It can be estimated by the transport rates of PBDEs in Caco-2cell lines.A total of80breast milk samples were collected from Shanghai, China, during2006–2012. The sum concentrations of14PBDE congeners in the breast milksamples varied widely from0.61–25.53ng/g lw, with a mean of4.91ng/g lw. Andthe mean concentration of tri-to hepta-BDEs was3.27ng/g lw for all samples. ThePBDE concentrations decreased from14.8to4.85pmol/g lw from2006–2012, witha decrease to the half concentration needing for approximately4years. BDE209wasthe predominant congener in breast milk. However, it was detected only in54.3%samples. The next predominant congeners were BDE153and47, which detected in100%and96%breast milk samples. The three congeners constituted61.2%of thetotal amount of the PBDEs in breast milk collected during2006–2012. The sum ofBDE47and153was suggested as a useful indicator for PBDE contamination inbreast milk. There were significant differences between primiparous and multiparousmothers for BDE28and tri-to hepta-BDEs (P＜0.05), although there were nosignificant correlations between the total PBDE concentrations in breast milk and theage, parity, and pre-pregnancy BMI of mothers. However, higher PBDE levels weregenerally observed in breast milk from primiparous mothers, while they were usuallyyounger than those of multiparous mothers (27.1vs.29.8years).The intestine is the main site of food digestion and absorption. The Caco-2cell line shares similar characteristics with human small intestinal epithelial cells interms of morphology and function. The model has been widely used to study theintestinal uptake, transport, bioavailability of environmental pollutants. Thepermeability of PBDEs (10ng/ml) from the apical (AP) to basolateral (BL) side wasmeasured under37oC for1,2,4,8,12and24h using Caco-2cells. The transportrates of PBDEs over the cell layer were between0.36%and18.9%, and increasingwith the exposure time. The transport rate of low brominated congeners was higherthan those of high brominated ones. PBDEs belong to poorly absorbed compounds,except for BDE17, which is the moderately absorbed compound. In addition, aftercorrected the data based on recovery, the amounts of PBDEs which sorption to cellswas increased with bromine atoms. The permeability of PBDEs with concentrationsof2.5,5,10and20ng/mL from the AP to BL side was also measured under37oCfor12h using Caco-2cells. The transport rates of PBDEs over the cell layer werebetween2.77%and17.9%. The transport rates of low brominated congeners werehigher than those of high brominated ones. The mean bioavailability of Σ3-7PBDEswas between7.0%and8.92%. The present study suggested that the main transportmechanism of PBDEs in Caco-2cells（APâ†'BL）was probably passive diffusion. Inaddition, the study found that there was a significant negative linear relationship（P＜0.001）between the transport rate and logKOWof PBDEs.The daily intake and daily uptake of PBDEs by infant via breast milk werecalculated and the associated risk estimated via hazard quotient value(HQ)wasassessed. The mean Σ3-7PBDEs of daily intake and daily uptake was12.9and0.65ng/kg-bw/day, respectively. The value of HQ was below1both considering the dailyintake and uptake of PBDEs, implying no obvious risk caused by PBDEs.