Accumulation of mercury, selenium and PCBs in domestic duck brain, liver and egg from a contaminated area with an investigation of their redox responses

PCBs and methylmercury (MeHg) are two of the most ubiquitous contaminants in the Qingzhen (QZ) area of Guizhou province. The estimated tolerable daily intakes (TDIs) of total mercury (T-Hg), MeHg, PCBs and Se from contaminated rice, eggs and fish by Chinese people in QZ showed that both MeHg and PCBs exceeded the corresponding safety limits. Pearson's correlation analyses of mercury and Se in all duck tissues showed that there were high correlations with T-Hg or MeHg and Se in QZ samples. However, the molar ratio between T-Hg and Se in brain tissues was close to 1, suggesting that Se is antagonistic to mercury toxicity only in brain tissues. Biochemical analyses showed that both superoxide dismutase and glutathione peroxidase increased in the brain, whereas in the liver and egg these enzymes decreased. However, lipid peroxidation and H2O2 generation in liver and egg tissues showed contrary responses, where significant increases in these tissues were seen relative to controls. Mercury and PCBs co-accumulation in liver and egg tissues gave rise to large numbers of free radicals as well as aggravated alkyl free radicals, superoxide radical and nitric oxide, thereby resulting in oxidative stress in these tissues. It can be concluded that an adaptive response of the redox defense system is present in brain tissues, as opposed to a general break down of the redox defense system in liver and egg. The results obtained in this study will provide basic information on exposure and risk assessment in local residents.

Graphical abstractA potential health impact probably existed in the QZ population and in poultry due to contaminated food consumption.Figure optionsDownload full-size imageDownload as PowerPoint slideEstimated total daily dietary intake (μg/kg/day) of T-Hg, MeHg, T-Se and PCBs from food according to the US EPA, FAO/WHO, US NAS and Germany limits, respectively (T-Hg, 0.71 μg/kg/day; MeHg, 0.1 μg/kg/day; T-Se, 0.83–3.3 μg/kg/day; PCBs, 1–3 μg/kg/day).Highlights► The contents of T-Hg, MeHg, and PCBs in tissues from a contaminated area were high. ► The estimated daily intakes of MeHg and PCBs exceeded the corresponding safety limits. ► An adaptive response of the redox defense system was present in brain tissues. ► A general break down of the redox defense system was present in liver and egg.