Analysis of perfluorinated compounds in Japanese surface waters and wild rodent blood samples collected as part of a nationwide survey

Abstract

Fluorochemicals, such as poly- and per-fluorinated compounds (PFCs), have been widely manufactured and applied for industrial and commercial uses for more than half a century due to their persistent properties, thus resulting in their ubiquitous detection in both abiotic and biological environmental matrices. The fairly low vapour pressure of PFCs is one of the important properties to suggest that water is the main environmental compartment for their partition and then bio-accumulated along the food chain. Previous results suggested that mere detection of a small group of PFCs, such as perfluoroocatnoate acid (PFOA) and perfluorooctanesulfonate (PFOS), is not enough to understand PFC contamination in water. To date, information on levels of short-chain PFCs in waters, like perfluoroethanesulfonate acid (PFEtS), perfluoropropanesulfonate (PFPrS), perfluoropentanoic acid (PFPeA), perfluorobutanoic acid (PFBA) and perfluoropropionic acid (PFPrA), is still limited. These short-chain PFCs are expected to be more water-soluble than the long-chain PFCs and so far only rainwater from North America have been detected. This finding indicates that atmospheric deposition is a likely non-point source (NPS) of short-chain PFCs in surface waters, especially surface runoff waters (SRWs). Water from rivers is also one of the important water matrices to study PFC contamination, since rivers may receive effluents from wastewater treatment plants, SRWs and NPS contamination. However, data on contributions of short-chain PFCs to total PFC levels in these water bodies are still scarce. Although PFCs are used worldwide, the amounts and types of PFCs that are produced vary among countries depending on industrial needs and scales, suggesting that PFC contamination patterns in the environment are expected to be different among nations. Due to their continuous input into the environment, PFCs have been measured in biota at several trophic levels, including higher predators. Previous studies have focused on measuring PFC concentrations in marine mammals and humans. Bio-monitoring studies on PFCs in terrestrial wild animals are comparatively scarce, however. Previous studies generally reported that levels of PFCs in biota that lived near point sources, and in more urbanized and industrialized regions, were exposed to greater PFC levels than those inhabiting remote areas. Detection of PFCs in terrestrial mammalian fauna has raised questions about their exposure pathways. Inhalation and consumption of PFC-contaminated foodstuffs and water have been proposed to be sources of exposure to PFCs in recent studies. These kinds of studies have been conducted mainly with respect to humans, but not to wild animals. Wild rats and mice are important members of the terrestrial food web. Due to their specific habitat use, they can act as indicators for detection of the extent of PFC contamination in their local environment. Furthermore, one source of exposure to PFCs in wild rodents may be via drinking waters because water is the most basic and essential for the survival of any living organism. Accordingly, wild rats and mice were collected nationally from 47 prefectures (3 locations per prefecture) in Japan together with water samples near their nesting places during 2004-2007. The present study consists of two main parts: (i) to compile comprehensive PFC contamination profiles for river and surface runoff water samples using Oasis® WAX solid phase extractions and liquid chromatograph coupled with tandem mass spectrometry, with particular emphasis on the extent and importance of short-chain PFC contamination in these surface waters; and (ii) to assess the relationships between PFC concentrations in the wild rodents with those in their water sources in order to study potential effects of PFCs via consumption of drinking water in wild rodents by utilizing pharmacokinetic modeling. In the first part of the study, concentrations of 28 PFC derivatives were measured in 31 river water and 29 SRW samples in Japan. The levels of total PFCs ranged from <2 to 65.2 ng/L in river waters and from <0.5 to 184 ng/L in SRWs. Among Japanese water studies, most of the short-chain PFCs (C2-C5) were reported for the first time in this study, contributing up to 56% of the total PFCs. PFPrA and PFBA were predominant and frequently detected, along with the long-chain PFOA and perfluorononanoic acid (PFNA), suggesting their wide contamination in Japanese waters. Significant and positive correlations between PFOA and PFNA were noted in both rivers and SRWs (R2=0.822, p<0.01: R2=0.911, p<0.01, respectively). In contrast, significant positive correlations of PFPrA and PFBA with PFOA, perfluorohexanoic acid (PFHxA) and perfluorodecanoic acid (PFDA) were only found in rivers (p<0.01) while these two short-chain PFCs were positively correlated with PFOS, PFNA, PFOA and perfluoroheptanoic acid (PFHpA) in SRWs (p<0.05). Different composition profiles of short-chain PFCs were observed between rivers and SRWs, indicating different PFC sources to these aquatic systems. In addition, a preliminary hazard assessment of PFOS exposure indicated that PFOS levels in rivers do not pose any significant risk to aquatic organisms and avian wildlife. In the second part of the study, concentrations of 21 PFC derivatives were measured in 127 blood samples of three wild rodent species, including 94 Rattus norvegicus (RN), 27 Apodemus argenteus (AA) and six Rattus rattus (RR), collected from 33 cities in 24 prefectures across Japan. Wild rodent blood samples from Chiba City (Chiba) and Hachioji City (Tokyo), located in heavily urbanized and industrialized parts of Japan, contained the greatest concentration of PFOS, perfluorooctanesulfonamide (PFOSA), N-ethyl perfluorooctanesulfonamidoacetate (N-EtFOSAA), PFOA, PFNA, PFDA, perfluorododecanoic acid (PFDoDA) and perfluoroundecanoic acid (PFUnDA), indicating that wildlife living in more populated and industrialized locations have greater exposure to PFCs. PFOS, PFOSA, PFOA, PFNA, PFDA, PFUnDA and PFDoDA were prevalent in all of the blood samples, but they varied in concentration among the wild rat species. PFOS and PFNA were dominant in RN and RR rat blood samples, while PFOA and PFUnDA were dominant in AA mouse blood samples. No age-related associations were found for PFCs in any of the wild rodent blood samples. Gender-related differences in PFC concentrations were only observed in adult RN, with males significantly (p<0.05) higher for PFDS, PFOS, perfluorohexanesulfonate (PFHxS), N-EtFOSAA, PFDoDA, PFDA, PFNA, PFOA and PFHpA. Eighty-nine of the collected rodents — 70 RN and 19 AA — coming from 23 cities in 19 prefectures together with their nearby water samples were selected to evaluate exposure to and potential effects of PFCs in the rodents via drinking these water sources. Use of a pharmacokinetic model allowed the contributions of PFOS and PFOA to total PFCs in the rodent blood via drinking water to be estimated. It was found that the contribution of PFOS (0.26%) and PFOA (0.28%) via water consumption to PFC levels in rodent blood was small. The detection of PFOS and PFOA in the blood sample could be from sources other than drinking water. Other exposure pathways, like inhalation and food, might be important for the rats and mice to accumulate PFOS, and hence future studies are necessary to understand the sources and exposure routes of PFCs to wild rats. The levels of PFOS and PFOA in the water sampled did not pose risks to the wild rodents due to direct consumption. To my knowledge, this is the first report to provide environmental monitoring data on short-chain PFCs in aqueous systems in Japan and to perform a preliminary estimation of the risks posed by PFC exposure of aquatic organisms and avian wildlife. Furthermore, this is the first study to analyze PFCs in wild rodent blood samples in Japan and to characterize their potential exposure routes. As part of the continuous monitoring surveys, future studies should be carried out to elucidate potential sources of PFCs in surface waters and their exposure pathways for wild rodents and other terrestrial species.