| Summary: | 碩士 === 國立成功大學 === 環境醫學研究所 === 90 === Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) are broadly distributed environmental contaminants. PCDDs/PCDFs/PCBs are highly stable in the environment. They are lipophilic and can be bioaccumulated via food chain into human bodies with long half-lives of elimination. The adipose tissue, blood, and breast milk are usually analyzed for the assessment of human exposure to PCDDs/PCDFs/PCBs. Among these three types of specimen, analysis of breast milk for exposure assessment provides two specific advantages. First, the collection of breast milk is noninvasive. Second, the analytical data can be used to assess the exposure of both the mother and the infant. The objectives of the study are (1) to measure the PCDDs/PCDFs/PCBs levels in breast milk samples collected in Tainan area, and (2) to utilize these data to evaluate infant’s exposure via breast-feeding.
The samples were collected from NCKU, Sin-Lau, and Chi-Mei hospitals in Tainan city. Breast milk samples were collected from 41 volunteers in these hospitals in years 2000 and 2001. Breast milk lipids were extracted by ethanol and n-hexane, followed by sulfuric acid digestion. For the analysis of 17 PCDDs/PCDFs, the extracts were fractionated with ion exchange (SCX), silica (Si), and Florisil solid phase extraction columns, and the fraction containing dioxins and furans were analyzed by gas chromatography-high resolution mass spectrometry (GC-HRMS). For the analysis of PCBs, only Florisil column fractionation was used, and 36 PCB congeners were analyzed by gas chromatography electronic capture detector (GC-ECD).
The average age of the subjects in this study was 30 years (N = 37, SD = 3.6 yrs). The total concentration of 17 dioxin congeners in the breast milk was 213 �b 141 pg/g-lipid. The concentration can be expressed as 12.7 �b 8.40 pg-I-TEQ/g-lipid when the international toxic equivalences (I-TEQs) of 2,3,7,8-tetrachlorinated dibenzo-p-dioxin (TCDD) is calculated, or 14.6 �b 9.26 pg-WHO-TEQ/g-lipid using WHO toxic equivalences (WHO-TEQs). The total concentration of 36 PCB congeners in breast milk was 96.8 �b 96.0 ng/g-lipid. The data represent these mothers’ exposure, and infants’ exposure through breast-feeding nursing can be estimated. Assuming that the breast milk intakes per day for an infant are 805 mL in the first two months after birth, 810 mL in the third month, and 925 mL from the 4th to the 6th month respectively, with an absorption efficiency of 95 %, the average infant’s dioxin/furan exposure was estimated to be 216 �b 129 pg-I-TEQ/day (or 250 �b 148 pg-WHO-TEQ/day). Due to the weight difference between boys and girls, these values translate into 34.9 �b 20.7 pg-I-TEQ/kg/day (40.5 �b 23.8 pg-WHO-TEQ/kg/ day) for boys, and 40.1 �b 23.8 pg-I-TEQ/kg/day (46.5 �b 27.3 pg-WHO-TEQ/kg/ day) for girls. Using the same model, the average infant’s exposure to 36 PCBs was estimated to be 2671 �b 2526 ng/day, or 431 �b 408 ng/kg/day for boys and 495 �b 465 ng/kg/day for girls.
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