Organochlorines in free-range hen and duck eggs from Shanghai: occurrence and risk assessment

As an important part of the residents' diet in China, the consumption of hen and duck eggs has been increasing rapidly in the past decades. Being rich in protein and lipid, eggs may be one of the main exposure routes for persistent organic pollutants (POPs) to human beings. In this study, four kinds of free-range hen and duck eggs were collected from two traditional egg-producing areas in Shanghai, namely Dianshan Lake Area and Jinshan Industry Zone. Organochlorine pesticides (OCPs, 18 compounds) and polychlorinated biphenyls (PCBs, 14 compounds) were analyzed with 41 egg samples. Among all OCPs, dichlorodiphenyltrichloroethanes (DDTs) were the dominant contaminant, with the concentrations ranging from 100 to 730 ng/g, lw. Unlike the 4,4'-DDE as the predominant DDTs congener in other three kinds of eggs, the duck eggs from Jinshan Industrial Zone had an abnormally high concentration of 2,4'-DDD, which may be related to ducks' feedings in the water. The levels of hexachlorocyclohexanes (HCHs) and pentachloroanisole (PCA) in eggs from different places were similar to each other, while hexchlorobenzene (HCB) for hen eggs from Dianshan Lake was much higher than other eggs. According to the results, the DDTs residues detected in this study were mainly due to the historical usage, whereas the high ratio of γ-HCH/α-HCH suggested that there might be some recent input of lindane in these two areas. For PCBs, the congener profiles varied among species. Low molecular PCBs (Tri-PCBs and Tetra-PCBs) were main congeners for duck eggs from Dianshan Lake and all hen eggs, while high molecular PCBs accounted for more than 50 % for duck eggs from Jinshan Industrial Zone, which was consistent with the water analysis results of the synchronous study from our group. This study suggests that Dianshan Lake Area may not be a good reference area for POPs monitoring in Shanghai. The estimated daily intakes of DDTs, HCHs, HCBs, and PCBs were far below the reference limits, showing no significant health risk for human consumption by eating eggs collected in this study.