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Title: Assessment of health risks and human exposure associated with perfluorinated compounds (PFCs) in tap water from China and other countries
Other Titles: Quan fu hua he wu zai Zhongguo ji qi ta guo jia zi lai shui suo yin zhi de jian kang feng xian ji qi dui ren ti bao lu liang de ping gu
Authors: Mak, Yim Ling (麥艷玲)
Department: Department of Biology and Chemistry
Degree: Master of Philosophy
Issue Date: 2009
Publisher: City University of Hong Kong
Subjects: Water -- Fluoridation -- Health aspects.
Fluorine compounds -- Physiological effect.
Notes: CityU Call Number: RA591.7 .M34 2009
xiv, 149 leaves : ill. (some col.) 30 cm.
Thesis (M.Phil.)--City University of Hong Kong, 2009.
Includes bibliographical references (leaves 124-145)
Type: thesis
Abstract: Perfluorinated compounds (PFCs) are a group of emerging pollutants that have received considerable attention recently. Besides the two well-known PFCs, perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA), other perfluorinated acids, including short-chain (< eight carbons) or long-chain (≥ eight carbons) sulfonates or carboxylates, have been found in aqueous environment over the world. PFOS and PFOA have been detected not only in raw waters, but also in treated drinking water from Germany, Italy, Spain, Poland, Japan, Malaysia, Thailand, Vietnam and Canada. Because of the low removal efficiency of PFCs by conventional drinking water purification processes like coagulation, sedimentation and chlorination, other PFCs may also be present in purified water, resulting in human exposure. Even though these PFCs usually occur at ppt levels, contamination of PFCs in drinking water has nevertheless prompted concern in both developed and developing countries, as water consumption occurs daily over the course of a lifetime and PFCs are bioaccumulative and have half-lives up to several years, resulting in chronic exposure to these compounds. Recent development of a sensitive and accurate analytical method for trace analysis of 20 PFCs, including several short- and long-chain compounds and their precursors, enabled their quantification in tap water samples collected from 2006−2008 in China, Japan, India, USA and Canada. The target analytes of the present study included eight perfluoroalkyl sulfonates (PFASs) and twelve perfluoroalkyl carboxylates (PFCAs), which were separated, identified and quantified by employing solid phase extraction (SPE) together with high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS). Of the measured PFCs, sixteen were present at detectable concentrations in tap water samples: PFOS, perfluorohexane sulfonate (PFHxS), perfluorobutane sulfonate (PFBS), perfluoropropane sulfonate (PFPrS), perfluoroethane sulfonate (PFEtS), perfluorooctane sulfonamide (PFOSA), N-ethyl perfluorooctane sulfonamidoacetate (N-EtFOSAA), perfluorododecanoic acid (PFDoDA), perfluoroundecanoic acid (PFUnDA), perfluorodecanoic acid (PFDA), perfluorononanoate (PFNA), PFOA, perfluoroheptanoic acid (PFHpA), perfluorohexanoic acid (PFHxA), perfluoropentanoic acid (PFPeA), and perfluorobutanoic acid (PFBA). Tap water from Japan contained the highest number of detectable PFCs (sixteen PFCs), whereas only seven PFCs samples were detected in samples collected from India. PFOS and PFOA were the two most frequently detected PFCs, and were quantified in more than 80% of the tap water samples from China, Japan, USA and Canada. However, these two compounds occurred in less than 40% of the Indian tap water samples. Tap water from Shanghai (China) contained the highest concentration of total PFCs (mean = 130 ng/L), whereas samples from Toyama (Japan) contained only 0.612 ng/L of total PFCs. Although waters from India usually contained relatively low concentrations of PFCs, high level of PFHxS was measured in tap water from Chennai (n = 1), indicating the presence of specific source(s) of PFCs influencing the quality of Indian tap water. Distinct PFC composition profiles in the tap water samples from the various countries were observed, likely because of variation in the production and usage of PFCs in these countries. Other than PFOS and PFOA, short chain PFCs like PFHxS, PFBS, PFPeA and PFBA were prevalent in tap water samples, reflecting the importance of identifying short-chain PFCs in tap water. Comparison of PFC concentrations with provisional health advisory, health-based values (HBVs) and advisory guidelines derived for PFOS, PFOA, PFBA, PFHxS, PFBS, PFHxA and PFPeA by the U.S. EPA and Minnesota Department of Health (USA) showed that the corresponding maximum measured concentrations of these compounds in tap water from China, Japan, India, USA and Canada were all below these guideline values. Risk quotients (RQs) of PFOS, PFOA, PFBA, PFHxS, PFBS, PFHxA and PFPeA due to consumption of these tap water samples were less than unity, showing that there may be no immediate risk posed to consumers by PFCs. Based on a simplified one-compartment toxicokinetic model in which it was assumed that PFCs were totally absorbed from the intestine, the estimated serum PFOS and PFOA levels in were calculated for consumption of Chinese tap water and compared with measured serum concentrations of PFCs in Chinese human blood samples reported by previous studies. The results indicated that drinking PFC-contaminated tap water contributed less than 1% of the serum PFOS concentrations in human blood from several Chinese cities, with the exception of those from Nanjing, where 8.2% of serum PFOS concentrations was found to be due to drinking water. However, tap water may be a relatively significant exposure pathway of Chinese citizens to PFOA, as at least 13% of PFOA in serum could be attributed to drinking tap water. Boiling tap water before consumption is a common practice in China which may alter PFC concentrations and composition profiles in tap water. Boiling water with a mixture of 17 native PFC standards and 4 mass-labeled PFC standards for 15 minutes was shown to cause a significant reduction in the concentrations of volatile PFCs such as PFOSA and N-EtFOSAA, but the levels of perfluorinated acids were not significantly different after boiling. Drinking boiled water, in turn, leaded to a change in PFC as this treatment may help to minimize the exposure to volatile PFCs, although the exposure of the non-volatile perfluorinated acid still occurred via the water consumption. To conclude, PFCs have been identified and quantified in tap water from China, Japan, India, USA and Canada, reflecting that PFC contamination in tap water is a global issue. Risks associated to PFOS, PFOA, PFBA, PFHxS, PFBS, PFHxA and PFPeA in tap water from these countries were low, but further studies should be carried out so as to characterize the risks posed by PFC mixtures. Drinking PFC-contaminated tap water may be a relatively important PFOA exposure pathway to Chinese and researches related to the toxicokinetic of other PFCs should be performed in order to provide more information for the estimation of contribution of drinking water to human PFC exposure.
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