Environmental concentrations, method development, trophic biomagnification, and mass balance analysis of poly- and perfluorinated alkylated substances in environmental samples

• Main Author: Loi, I Ha (呂綺霞)
• Format: Thesis
• Language: unknown
• Published: City University of Hong Kong 2012
• Subjects: Organofluorine compounds > Analysis; Arctic; Fang; Victoria Harbour; Human health; Phytoplankton; Zooplankton
• Online Access: http://hdl.handle.net/2031/6890; http://lib.cityu.edu.hk/record=b4199872

Poly- and perfluorinated alkylated substances (PFASs) are useful chemicals that have been manufactured and widely used for various applications for over 60 years. Concerns over PFASs have been growing since the 1990s because of their ubiquitous occurrence, toxicities, environmental persistence and bioaccumulation in wildlife and humans. There is thus increasing interest in studying the distribution, behaviour, fate and risks of PFASs in the global environment. The goals of the present study consisted of three main parts: 1) to develop a method to extract PFASs from plant tissues; 2) to investigate the partitioning behavior and trophic transfer properties of PFASs, as well as to conduct mass balance analysis of fluorine in a subtropical food web; and 3) to survey and screen for novel PFASs in different environmental matrices, commercial products and human blood samples. Few studies have reported PFAS extraction methods for plants because of the difficulties in analyzing complex sample matrices such as plant tissues. However, plants are the primary producers in food webs, and therefore knowledge of PFAS concentrations in plants is important to understand the sources and fates of these compounds. In view of this, a new extraction method using acetonitrile followed by ENVI-Carb, solid phase extraction-weak anion exchange and ENVI-Carb clean up was developed using a local grass species from Mai Po, Phragmites australis (see Chapter 3). The newly developed method requires only 1 - 2 g dry weight (d.w.) of P. australis for quantification of up to 20 PFASs, including perfluoroalkyl sulfonates (PFSAs): C2 - C4, C6, C8 and C10; perfluoroalkyl carboxylates (PFCAs): C3, C4, C6 - C12 and C14; N-ethyl perfluorooctanesulfonamidoacetate (EtFOSAA); and 6:2, 8:2 and 10:2 fluorotelomer unsaturated carboxylate, with matrix recoveries ranging from 71 - 102%. The method developed was applied to different types of plant samples including grasses (i.e. P. australis, Paederia scandens and Panicum maximum) and to phytoplankton from a tidal shrimp pond in Mai Po Marshes Nature Reserve (MPMNR), as well as green tea (in powder form). Studies in temperate and Arctic regions have shown that PFASs can biomagnify in aquatic food webs, especially perfluorooctanesulfonate (PFOS) and some long-chain PFCAs. However, limited information is available on PFAS bioaccumulation in subtropical areas, which are large areas globally and are highly productive systems. The potential biomagnification of PFASs in a subtropical food web was investigated using both established methods and a newly developed method for phytoplankton analysis (see Chapter 3). Various environmental matrices including surface water (n = 10), sediment (n = 4) and biota comprising a small food web, including phytoplankton (pooled samples (p) = 1), zooplankton (p = 1), gastropods (p = 3), worms (p = 6), shrimps (p = 4) and fish (n = 29) were collected from a tidal shrimp pond in the MPMNR in Hong Kong (HK), and analyzed for a suite of PFASs. Consistent with other previous studies of biological samples, PFOS was the dominant PFAS in most of the biota samples at concentrations ranging from 0.09 to 87.1 ng/g w.w. Composition profiles differed among animal groups while relatively similar composition profiles were observed within each group. Trophic magnification was observed for PFOS, perfluorodecanoate (PFDA), perfluoroundecanoate (PFUnDA) and perfluorododecanoate (PFDoDA) based on the calculated trophic magnification factor (TMF) values ranging from 1.30 to 1.75 for this food web. PFUnDA (TMF = 1.75) was found to have the greatest TMF. Environmental risk assessment of PFOS, PFDA and PFOA indicated that concentrations of these compounds in MPMNR were unlikely to pose a risk to waterbirds, and human health risk assessment of PFOS and PFOA similarly indicated a low potential risk to humans consuming shrimp and fish. These results provide insight into the accumulation properties and trophic transfer of these compounds in an aquatic food web, and help to characterize the accumulation profiles of PFASs in different aquatic ecosystems (see Chapter 4). In addition to known PFASs, recent studies have demonstrated the presence of unidentified organic fluorines (OFs) in wildlife. In order to have a better understanding of the presence, fate and transfer of OF contaminants in the environment, a mass balance approach for fluorine was employed with the environmental samples from the MPMNR (see Chapter 5). The extent of environmental contamination by known and unknown fluorochemicals as well as the potential transfer of these compounds in an aquatic food web was evaluated. The contribution of known PFASs to EOF increased significantly with increasing trophic level [i.e. fish liver (41 - 76%) > shrimp (10 - 12%) > worm (0.5 - 3.7%) > soft tissue of gastropod (0.4%)]. However, only 10 to 12% of the EOF in the shrimp samples was of known PFASs, indicating the need for further investigation to identify unknown fluorinated compounds in wildlife. A recent study reports detection of a new class of PFASs, the polyfluoroalkyl phosphoric acid diesters (diPAPs), in paper fibre, sewage sludge and human blood sera at up to parts-per-billion (ppb) levels, comparable to those of widely-used compounds such as PFOA. It is hypothesized that diPAPs account for part of the unknown OFs. To test this hypothesis, surface water, sediment and worms were collected from the same tidal shrimp pond in MPMNR in 2012 for diPAP analysis (see Chapter 6). Although the detected concentrations of diPAPs were low, the presence of diPAPs in worms demonstrates their contribution to the unknown OFs. In order to further understand diPAP occurrence in HK, surface water (n = 15) and marine sediment samples (n = 30) were collected from three locations in Victoria Harbour, the main waterway in HK, and sewage sludge was collected from three sewage treatment plants. The prevalence of diPAPs (both 6:2 and 8:2) was observed in both sediment and water samples. The level of diPAPs detected in HK sludge was at ppb levels, suggesting that there is extensive usage of these commercial fluorinated materials in HK. Since diPAPs are used for coating food contact packaging to provide oil and water resistance, recent studies have shown that paper and paperboard food packaging is a source of human and environmental exposure to these fluorinated surfactants via migration from these materials to the food. Therefore, the PFAS concentrations of 23 paper products, including food contact paper (n = 20) and non-food contact paper (p = 3) were analysed. The results showed that different diPAP congeners were detected in food contact paper products with decreasing concentrations of 6:2/8:2 diPAP > 8:2 diPAP > 6:2 diPAP. Since the migration of PFASs was found to increase with increasing temperature, diPAP concentrations were determined for six brands of microwavable popcorn bags from mainland China both before and after popping. However, no significant difference of PFAS concentrations was observed in the popcorn bag both with and without microwave treatment in the present study (Mann-Whitney Rank Sum Test, p > 0.05). Many of the human exposure models to date have suggested that the dominant source of human exposure to PFASs is through dietary intake. DiPAPs, commonly found in food packaging, are known PFCA precursors and are possible sources of human exposure to PFCAs. A preliminary study of human exposure was therefore carried out by measuring diPAPs in 20 human blood samples collected in HK (see Chapter 6). The two most prevalent congeners in whole blood samples were 6:2 diPAP and 8:2 diPAP, while 6:2/8:2 diPAP was not detected in any sample. The diPAP concentrations in whole blood samples reported here were comparable to those measured in human sera in Germany. In contrast with our finding, 8:2 diPAP was the dominant species in the human sera in the U.S., suggesting that there are regional differences in diPAP exposure sources. Despite the low concentrations of diPAPs we observed, their presence in human whole blood provides direct evidence of human exposure to commercial fluorinated products. With the availability of new analytical standards, more new PFASs can be monitored and analyzed. Standard addition (0x, 0.5x, 1x, 2x and 5x) was used to make preliminary measurements of fluorotelomer sulfonates (FTSAs) and perfluoroalkyl phosphinates (PFPiAs) in the sample extracts. Interestingly, PFPiAs (C6/C8: 52 - 1900 pg/g w.w., C8/C8: 31 - 300 pg/g w.w.) were found in worm samples from the MPMNR but not in any other environmental sample. In contrast, FTSA was detected in a variety of the samples (i.e. worms: 6:2 FTSA > 8:2 FTSA; food packaging: 6:2 FTSA > 8:2 FTSA; microwavable popcorn bag: 6:2 FTSA > 8:2 FTSA; human blood: 8:2 FTSA > 6:2 FTSA). The difference in the dominant FTSA congener in human blood compared with that in the food packaging samples analyzed, suggested that food packaging was not the major exposure source of FTSAs, but further pharmacokinetic studies on FTSAs in mammals are needed to address this point. To conclude, the present study provided new insights regarding trophic transfer of PFASs in a subtropical food web; the presence of a large proportion of unknown OFs in environmental samples; the detection of diPAPs in different environmental matrices, commercial products and human blood in HK; as well as the discovery of new PFASs, FTSAs and PFPiAs in food packaging and human blood. However, the method for the analysis of FTSAs and PFPiAs requires further optimization, and the small sample sizes of sludge, human blood and food contact paper products analyzed in the present study limit the applicability of the data. Further studies on commercial fluorochemicals are necessary to expand the data set to different types of exposure media such as personal care and cosmetic products in order to identify the major exposure sources of novel PFASs to humans and wildlife. CityU Call Number: QD305.H15 L64 2012 xxxiv, 259 leaves : ill. (some col.) 30 cm. Thesis (Ph.D.)--City University of Hong Kong, 2012. Includes bibliographical references (leaves 224-259)