Maternal Transfer And Biotransformation Of Selected Organic Pollutants In Early Life Stage Of Chicken

Avian eggs have been widely used as a biomonitor tool to investigate environmental contamination with pollutants.Because the contaminants in eggs could only come from female avian,it is therefore important to know maternal transfer of contaminants for both environment monitoring and evaluation of health risks in early life stage of avian.Although many studies have reported the maternal transfer of organohalogenated pollutants?OHPs?in avian,the results were inconsistent and even contradictory with each other,which is possibly due to the differences of samples in female tissues and offspring.Few studies have investigated the influence of using different female tissues to evaluate maternal transfer of contaminants.Also,some studies showed different results on the effect of egg laying sequence to the concentrations and patterns of pollutants in eggs.Moreover,most of the studies on biotransformation of OHPs focus mainly on adult avian,and only a few studies concerned about early life stage,which is more sensitive to pollutants.For this purpose,experiments in two aspects were designed to study maternal transfer,biotransformation and tissue distribution of OHPs during egg formation and embryo development of chicken?Gallus domesticus?.On the one hand,target chemicals?PBDEs,PCBs,BTBPE and DPs?were injected into fertilized chicken eggs to investigate biotransformation and tissue distribution of the contaminants during embryo development through chemical mass balance and chiral analysis.On the other hand,adult hens were fed with spiked food and laid eggs were collected to evaluate concentrations and patterns of PBDEs,PCBs and DPs in eggs in relation to the laying sequence.Meanwhile,different hen tissues were used to calculate maternal transfer of the target chemicals.In addition,funded by China Scholarship Council,we also perform a preliminary study on the occurrence and partitioning of organophosphate esters and their metabolites in chicken eggs from across Australia.The uptake efficiencies of BDE209 and DPs were around 60%,which were lower than other chemicals?>80%?.Enantioselective metabolism was observed for all four chiral PCBs?CB95,CB91,CB149,and CB132?during embryo development.Metabolism for PCBs and BTBPE occurred in the first 18 days of development,while metabolism for PBDEs and DPs mainly occurred in the last 3 days.An OH-metabolite of BDE85 was confirmed and several other OH-metabolites were also observed,but no metabolite of DPs was found in this study.High levels of BDE209 were determined in eggshells,and the decrease of BDE209 in neonatal chicks can therefore be attributed to rapid excretion.Furthermore,through chemical mass balance calculation,we found that the metabolic rate of anti-DP?28%?was higher than that of syn-DP?12%?,which demonstrated the stereoselective metabolism for anti-DP in chicken.Chemical profiles were calculated in different tissues?heart,stomach,liver,remaining yolk,and carcass?of chicks,which showed that liver enrich all the chemicals while carcass defect all the chemicals except for BDE47,and heart enrich 3 PCBs?CB95,CB149,and CB132?.The difference in tissue distribution may be associated with the time of organ formation and lipid contents of different tissues.A significantly positive correlation was found between ratios of lipid normalized concentrations of chemicals in liver and carass and log K_OW of these chemicals,indicating that liver tends to accumulate higher lipophilic chemicals.For the experiment of hens and laying eggs,a periodical variation was observed in chemical concentrations and profiles in eggs following the egg laying cycle,and the variation patterns of BDE209 and DPs were obviously different from other PCB and PBDE congeners.The profile of PBDE congeners was dominated by BDE209 in the early time of egg laying,while BDE100 and BDE153 became the most abundant congeners in the late time of depuration.The contribution of more persistent PCB congeners?CB138 and CB180?and the percentage of anti-DP increased in laid eggs in relation to the laying time.These results were possibly due to metabolism in hens and difference in maternal transfer.Maternal transfer of OHPs were calculated by chemical concentrations in undeveloped ovum and other tissues of hens.When muscle,stomach,lung and heart were used to represent hens,a significantly negative correlation was found between maternal transfer capability and log K_OW of the chemicals(log K_OW>7).However,when liver,abdominal fat,intestine and kidney were used to calculate,no significant correlation was found,but higher maternal transfer capability were observed for DPs and BDE209.Together with the different variation patterns of BDE209 and DPs in eggs and the higher contribution of BDE209 in laid eggs of early time,we thought the later four tissues may reflect the actual situation of maternal transfer.OPEs and their metabolites have been ubiquitously detected in chicken egg yolk and albumin collected from across Australia,and the concentrations of metabolites were higher than that of OPEs,indicating widespread of these pollutants in the environment.The partitioning of OPEs between egg yolk and albumin correlated with chemical molecular mass?significantly negative correlation?,suggesting different behavior of OPEs in eggs from that of lipophilic OHPs.This study increase our knowledge about environmental fate and behavior of selected OHPs in embryo development and maternal transfer of avian,together with the preliminary study on occurrence and partitioning of OPEs in chicken eggs,will provide important basis for evaluating embryonic toxicity and potential health risks of these pollutants in early life stage of avian.