Concentrations And Distributions Of Perfluoroalkyl Acids In Eggs From China

Perfluoroalkyl acids(PFAAs) were widely used in textile, paper manufacturing, painting, and electroplating industries due to their hydrophobicity, lipophobicity and heat stability. With increasing discoveries of their toxicity, they have attracted strong attention as a new group of persistent organic pollutants(POPs). The Environmental Protection Agency(EPA) prohibited the production and use of perfluorooctane sulfonate(PFOS) in 2001, proposed the reduction plan for perfluorooctanoic acid(PFOA) in 2009, and achieved zero PFOA emission in the USA by 2015. The European Union(EU) prohibited the sale and use of PFOS in 2006, and so did China in 2014. PFAAs have strong affinity with proteins and thus can easily accumulate in the biota, making protein-rich, animal-derived food an important source for PFAAs intake. EU and other developed countries had started their investigation of PFAAs in animal-derived food since 2008 and 2012, respectively, but such studies are still scarce in China. In order to assess and monitor the risk of typical PFAAs such as PFOS and PFOA, basic data about the PFAAs residual levels in animal-derived food is required urgently. Therefore, as an important animal-derived component in the diet, the eggs need an investigation on their PFAAs residual level, which contributes to the food safety in China. In this thesis, the residual levels and distributions of 17 PFAAs in 1800 egg samples collected from 29 provinces of China were examined using high performance liquid chromatography-tandem mass spectrometry(HPLC-MS/MS) combined with dispersive solid phase extraction. The main results were as follows:(1) ΣPFAAs residue in eggs from the 29 provinces was 0.615 μg/kg in average and ranged from <LOQ to 51.3 μg/kg. PFOS and PFOA residues were 0.160 μg/kg and 0.0998 μg/kg in average, ranging from <LOQ to 33.0 μg/kg and <LOQ to 5.15 μg/kg, respectively. Perfluoropentanoic acid(PFPeA), PFOA, perfluorodecanoic acid(PFDA), perfluoroundecanoic acid(PFUdA), perfluorononanoic acid(PFNA) and PFOS were the major detected PFAAs, accounting for 28.5%, 16.2%, 6.00%, 5.87%, 4.86% and 26.0% of ΣPFAA, respectively. The detection rates of the 17 detected PFAAs were all below 50%, and 79% of ΣPFAAs were medium- and short-chain PFAAs. Principal component analysis showed that PFUdA(0.914) and PFPeA(0.899) were the two major components of PFAAs in eggs. After combining with Pearson’s correlation analysis, this result suggested that the PFAAs in eggs had extensive sources, including painting, electronic manufacture, petrochemical, etc.(2) Among the eggs from coastal provinces, the highest ΣPFAAs was detected in the samples from Jiangsu(average: 0.81 μg/kg; median: 0.19 μg/kg) and the lowest, Zhejiang(average: 0.17 μg/kg; median: 0.15 μg/kg). Among the eggs from inland provinces, the highest ΣPFAAs was detected in the samples from Xinjiang(average: 6.08 μg/kg; median: 1.15 μg/kg) and the lowest, Heilongjiang(average: 0.138 μg/kg; median: 0). The ΣPFAAs residue levels in inland eggs were higher than in coastal ones(p<0.05), showing that regional PFAAs residues are closely related to the distribution and scale of local fluorine industries, as well as the mass-application of PFAAs-involved products in the area. Among coastal eggs, the PFOS/PFOA ratio was the highest in Jiangsu(4.8) and the lowest in Shanghai(0). Among inland eggs, the ratio was the highest in Xinjiang(128) and the lowest in Gansu(0) and Heilongjiang(0). The PFOS/PFOA ratio of egg samples in Xinjiang was above 100, about 26 times of that in Jiangsu, suggesting recent introduction of PFOS into Xinjiang, on top of its relatively high residue in history.(3) The health risk assessment showed that the hazard ratios(HR) of PFOS, PFOA and other PFAAs detected in eggs were all below 1, indicating that the immediate harm via egg consumption was minimal. However, the HR of PFOS in Jiangsu, Anhui and Xinjiang were close to 1, which require higher attention and further research.