Study On The Exposure Level Of Short-chain Chlorinated Paraffins In Food

Short chain chlorinated paraffins(SCCPs)are chlorinated n-alkanes with carbon number of 10-13 and chlorine content of 30%-70%.Because of the characteristics of persistent organic pollutants(POPs)such as environmental persistence,long-distance migration,bioaccumulation and toxicity,SCCPs have attracted wide attention from scholars both at home and abroad.In May 2017,at the Eighth Meeting of States Parties to the Stockholm Convention,SCCPs were included in the list of controlled POPs in Annex A of the Stockholm Convention.The composition and structure of SCCPs are very complex,and they are easily interfered by other chlorinated compounds.Therefore,there are still great challenges in sample preparation and accurate quantitative analysis.SCCPs have been widely detected in different environmental samples,including sediment,water,air,soil,and sewage sludge,and even in human breast milk and food.Previous studies have shown that SCCPs are considered to have subchronic and chronic toxicity on the target organs such as the thyroid gland,liver,and kidney.Human exposure pathways to SCCPs are complex,including food intake,dust ingestion,and air intake.A recent study also reported that food intake was the major route of external SCCP exposure for the general population.Therefore,it is of great significance to establish the pretreatment method of SCCPs in food matrix and detect the concentration of SCCPs in food samples.The main research contents and results of this artile are as follows:1.First chapter.The physical and chemical properties of SCCPs were introduced;the potential POPs characteristics of SCCPs were briefly described,including environmental persistence,long-distance migration,bioaccumulation and toxicity;the research progress of pretreatment methods of SCCPs and the content of SCCPs in food were described in detail;the control measures in the production and use of SCCPs were introduced;the significance,research content and innovation of this article were finally described.2.Second chapter.The extraction methods of SCCPs in complex matrices were compared and the purification methods of SCCPs were optimized.The method was applied to the study of SCCPs concentration and homologue composition in fresh food samples of different origins.The results showed that the recovery of the accelerated solvent extraction(ASE)was 94.6%for solid matrix,which is better than that of ultrasonic extraction(63.4%).For liquid matrix,the recovery of the solid-phase extraction(SPE)was 70.2%,which is better than that of liquid-liquid extraction(57.1%).Furthermore,the pretreatment method of SCCPs extracted by ASE and purified by multilayer silica-Florisil composite column was established.The concentrations and congener profiles of SCCPs in the fresh food samples of different origins were investigated using the established method.The recovery of SCCPs in food samples was between 56%and 81%.The results showed that the average SCCP concentrations in imported and domestic fresh foods were 291.5 ng/g ww and 281.2ng/g ww,respectively.The main homologs of SCCPs in the sample were C₁₀ and Cl₇,which accounted for 33.5%and 30.8%of the total SCCPs,respectively.3.Third chapter.The method established in Chapter 2 was used to conduct a preliminary study on SCCPs concentrations and homologues in supermarket foods in Jinan,China.The collected samples were divided into five categories:vegetables,fruits,grains,seafood and meat.The lipid content,water content and SCCPs concentration of each sample were determined.Based on the results of the fifth total diet study,the estimated daily intake(EDI)and the margin of exposure(MOE)of SCCPs in five types of samples were studied.The results showed that SCCPs concentrations in all food samples ranged from 8.27 to 268 ng/g ww,60 to 7666 ng/g lw and 58.6 to 1977 ng/g dw.In this study,SCCPs concentrations(ww-basis and dw-basis)showed significantly linear correlation with the lipid content in different food species.Animal-origin food products contain higher SCCP levels than plant-origin food products.The SCCP congener group patterns varied among the five food matrices.The main homologs of SCCPs in the sample were C₁₀ and Cl₇,which accounted for 36.9%and 30.4%of the total SCCPs,respectively.The MOE values of SCCPs in the five food samples were all higher than the uncertainty value of 1000.The upper bound of the 95%confidence interval of the MOE calculated on the basis of the total food consumption(2.30×10⁴)was also higher than 1000.People exposure to SCCPs through dietary intake do not have a significant health risk in China,but other exposure routes such as dermal uptake should not be negligible.