Reevaluation on accumulation and depletion of dioxin-like compounds in eggs of laying hens: Quantification on dietary risk from feed to egg

Updated assessment on transfer of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) from feed to food is essential for understanding human exposure risk. A controlled feeding experiment was conducted for laying hens to reevaluate the transfer characteristics of dioxin-like compounds from feed to egg. Two fortified diets (1.17 and 5.13 pg TEQ g(-1) dry weight), made by blending with fly ash, were fed to laying hens for 14 days, followed by 28-days depletion. Levels of Sigma TEQ(PCDD/Fs+DL-PCBs) in eggs rapidly increased once exposure started, reaching at 1.98 and 6.86 pg TEQ g(-1) lw at the end of exposure for low and high-exposure groups, respectively, and dropped to under the European legislation (maximum levels: 5.0 pg TEQ g(-1) lw) after 28-days depletion. The quantitative depletions showed that the half-lives (T-1/2) of Sigma TEQ(PCDD/Fs) in eggs were 23 and 14 days for low-and high-exposure groups, respectively. The depletion and accumulation rates of PCDD/Fs were in the range of 0.026-0.151 and 0.005-0.016 day(-1), respectively, representing that the T-1/2 of PCDD/Fs in eggs ranged from 5 to 27 days. The depletion kinetics of DL-PCBs was not significant in egg. The hens with higher laying rates exhibited shorter T-1/2 of PCDD/Fs, implying that increasing laying rate could expedite the depletion of PCDD/Fs in egg. The T-1/2 of PCDD/Fs in egg were negatively correlated with the chlorine number, indicating that lower chlorinated congeners tended to be retained in the egg. Transfer rates of PCDD/Fs were in the range of 4-19%, which were lower than the previous results. These results were attributed to short exposure time and low bioavailability of PCDD/Fs in fly ash. Estimations of dietary intake highlighted the dietary risk of PCDD/Fs from feed to egg, which would pose limited adverse effects on human health. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The research highlighted the importance of updated assessments on transfer of toxic substances in poultry products to better understand human exposure risks. Results showed that different exposure levels of contaminants in feed can affect the transfer rate and depletion rate in eggs, with hens with higher laying rates expediting the clearance of toxic substances. Lower chlorinated congeners tend to be retained in eggs, while transfer rates of toxic substances were lower than previous studies, possibly due to short exposure time and low bioavailability of contaminants.