Study On Dietary Exposure And Maternal-neonatal Transfer Of Typical Perfluoroalkyl Substances Isomers

Perfluoroalkyl substances(PFASs)are agroup of chemicals that have been extensively used in many industrial and consumer products.Because of their widespread usage,PFASs have become ubiquitous and can be found in water,soil,wildlife and humans all over the world.PFASs are persistent and bioaccumulative,which may pose a potential health risk for human health.Perfluorooctane sulfonoate(PFOS)and perfiuorooctanoate(PFOA)are the most prominent PFASs in human samples.The isomers of PFOS and PFOA display different environmental behaviors,pharmacokinetics and toxicity.Thus,it is necessary to perform a meticulous analysis of PFOS and PFOA isomers in humans and the environment to conduct a more comprehensive risk assessment.In this paper,the analytical methods of main PFOS and PFOA isomers in complex dietary matrix and serum were established by ultra performance liquid chromatography-tandem mass spectrometry.The composition of main PFOS and PFOA isomers and their dietary exposure levels in three animal foods from the fifth total dietary study were analysed.Based on the study of dietary exposure in adults,the efficiency of different PFOS and PFOA isomers through placental transmission was studied by analyzing the composition of PFOS and PFOA isomers in maternal venous blood and matched cord blood.Thus,it provided a scientific basis for risk assessment of early PFASs exposure to life.In this study,the pollution levels of main PFOA and PFOS and its typical isomers in animal food(aquatic products,meat and eggs)in the fifth total dietary survey were analyzed.The results showed that branched PFOS was only found in he aquatic samples,and the proportion of n-PFOS in Henan,Beijing,Liaoning,Inner Mongolia,Shanghai,Jiangsu and Guangdong provinces was 74.44% ~ 92.28%.The branched PFOA was only found in the eggs of Qinghai Province,with the concentration of 4m-PFOA(10.64 pg/g,ww),5m-PFOA(21.21 pg/g,ww),iso-PFOA(66.70 pg/g,ww),n-PFOA(1332.78 pg/g,ww).Branched PFOS and branched PFOA were not detected in meat samples.Combined with dietary consumption data,the proportion of dietary intake of PFOS in Chinese residents is less than 7%,which was not enough to explain the high proportion of branched PFOS in the blood of humans,so the high proportion of branched PFOS in humansmay have other sources,and it was needed further investigation and study.At the same time,we also analyzed the levels of PFOA and PFOS and its typical isomers of the pregnant women and cord serum in Beijing.It is showed that branched PFOA was not detected in both pregnant women and cord serum,and the detection rates of n-PFOA were 100% with the mean concentrations of 1.55 ng/mL and 1.16 ng/mL,respectively.The mean concentration of n-PFOS was the highest(3.49 ng/mL),followed by 3m+4m-PFOS(0.66 ng/mL),5m-PFOS(0.54 ng/mL),iso-PFOS(0.42 ng/mL),1 m-PFOS(0.19 ng/mL).The percentage of n-PFOS was from 32.07% to 99.10%,the average percentage was 67.38%,followed by 3m+4m-PFOS(11.70%),5m-PFOS(9.55%),iso-PFOS(7.61%),and 1m-PFOS(3.75%).In cord serum,the composition of PFOS isomers was similar to that of maternal serum,with the highest concentration of n-PFOS(1.24 ng/mL),followed by 3m+4m-PFOS(0.36 ng/mL),5m-PFOS(0.25 ng/mL),iso-PFOS(0.15 ng/mL),1 m-PFOS(0.15 ng/mL).The proportion of n-PFOS in ?PFOS was from 22.02% to 89.54%,the average percentage was 58.78%,followed by 3m+4m-PFOS(15.96%),5m-PFOS(11.32%),iso-PFOS(7.00%),and 1m-PFOS(6.93%).There was a positive correlation of PFOS isomers in cord serum and pregnant women.The proportion of n-PFOS in cord blood(58.78%)was lower than that in n-PFOS(67.38%),indicating that the branched isomers were preferentially transferred from the pregrant women to the infants,and thus branch PFOS ratio in cord serum was increased.Through calculating the transfer efficiency of PFOS isomers through the placenta,it is found that the order of transmission efficiency is lm-> 3m+4m-> 5m-> iso-> n-.This paper analyzed the concentration of typical PFASs isomers in maternal serum and nine diets(the sixth total dietary study)in Fujian Province.The results showed that iso-PFOA was detected with the concentration range from <LOD to 0.50 ng/mL.The detection rate of n-PFOA was 100% with the concentration range from 1.25 ng/mL to 15.93 ng/ml.And its mean concentration was 4.29ng/mL.The percentage of iso-PFOA was 0.45%,and the percentage of n-PFOA was 99.55%.The average concentration of n-PFOS was 9.19 ng/mL,followed by iso-PFOS(0.54 ng/mL),3m+4m-PFOS(0.46 ng/mL),5m-PFOS(0.39 ng/mL),1m-PFOS(0.17 ng/mL).The average percentage of n-PFOS was 84.88%,followed by iso-PFOS(5.12%),3m+4m-PFOS(4.59%),5m-PFOS(3.72%)and 1m-PFOS(1.68%).PFOA and PFOS and its isomers were not detected in vegetables,fruits,cereals,beans and potatoes.n-PFOS(193.43 pg/g)was detected in aquatic products.n-PFOA was detected in meat and eggs,with contents of 67.43 pg/g and 190.79 pg/g,respectively.5m-PFOA(8.29 pg/mL)?iso-PFOA(12.39 pg/mL)and n-PFOA(132.16 pg/mL)were detected in milk.The results showed that the small amount of iso-PFOA in pregnant women in Fujian Province had a relationship to the consumption of milk products,and there was no branching PFOS in the nine diets,thus,diet is not the main source of PFOS for local residents.