| 1. |
- De Silva, Amila O., et al.
(författare)
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PFAS Exposure Pathways for Humans and Wildlife : A Synthesis of Current Knowledge and Key Gaps in Understanding
- 2021
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Ingår i: Environmental Toxicology and Chemistry. - : Pergamon Press. - 0730-7268 .- 1552-8618. ; 40:3, s. 631-657
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Forskningsöversikt (refereegranskat)abstract
- Here we synthesize current understanding of the magnitudes and methods for assessing human and wildlife exposures to poly- and perfluoroalkyl substances (PFAS). Most human exposure assessments have focused on two to five legacy PFAS and wildlife assessments are typically limited to targeted PFAS (up to ~30 substances). However, shifts in chemical production are occurring rapidly and targeted methods for detecting PFAS have not kept pace with these changes. Total fluorine (TF) measurements complemented by suspect screening using high resolution mass spectrometry are thus emerging as essential tools for PFAS exposure assessment. Such methods enable researchers to better understand contributions from precursor compounds that degrade into terminal perfluoroalkyl acids (PFAA). Available data suggest that diet is the major human exposure pathway for some PFAS but there is large variability across populations and PFAS compounds. Additional data on TF in exposure media and the fraction of unidentified organofluorine are needed. Drinking water has been established as the major exposure source in contaminated communities. As water supplies are remediated, and for the general population, exposures from dust, personal care products, indoor environments and other sources may be more important. A major challenge for exposure assessments is the lack of statistically representative population surveys. For wildlife, bioaccumulation processes differ substantially between PFAS and neutral lipophilic organic compounds, prompting a revaluation of traditional bioaccumulation metrics. There is evidence that both phospholipids and proteins are important for the tissue partitioning and accumulation of PFAS. New mechanistic models for PFAS bioaccumulation are being developed that will assist in wildlife risk evaluations.
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| 2. |
- Ruyle, Bridger J., et al.
(författare)
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Interlaboratory Comparison of Extractable Organofluorine Measurements in Groundwater and Eel (Anguilla rostrata) : Recommendations for Methods Standardization
- 2023
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 57:48, s. 20159-20168
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Tidskriftsartikel (refereegranskat)abstract
- Research on per- and polyfluoroalkyl substances (PFAS) frequently incorporates organofluorine measurements, particularly because they could support a class-based approach to regulation. However, standardized methods for organofluorine analysis in a broad suite of matrices are currently unavailable, including a method for extractable organofluorine (EOF) measured using combustion ion chromatography (CIC). Here, we report the results of an international interlaboratory comparison. Seven laboratories representing academia, government, and the private sector measured paired EOF and PFAS concentrations in groundwater and eel (Anguilla rostrata) from a site contaminated by aqueous film-forming foam. Among all laboratories, targeted PFAS could not explain all EOF in groundwater but accounted for most EOF in eel. EOF results from all laboratories for at least one replicate extract fell within one standard deviation of the interlaboratory mean for groundwater and five out of seven laboratories for eel. PFAS spike mixture recoveries for EOF measurements in groundwater and eel were close to the criterion (±30%) for standardized targeted PFAS methods. Instrumental operation of the CIC such as replicate sample injections was a major source of measurement uncertainty. Blank contamination and incomplete inorganic fluorine removal may introduce additional uncertainties. To elucidate the presence of unknown organofluorine using paired EOF and PFAS measurements, we recommend that analysts carefully consider confounding methodological uncertainties such as differences in precision between measurements, data processing steps such as blank subtraction and replicate analyses, and the relative recoveries of PFAS and other fluorine compounds.
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| 3. |
- Hu, Xindi C., et al.
(författare)
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Tap Water Contributions to Plasma Concentrations of Poly- and Perfluoroalkyl Substances (PFAS) in a Nationwide Prospective Cohort of U.S. Women
- 2019
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Ingår i: Journal of Environmental Health Perspectives. - : National Institute of Environmental Health Science. - 0091-6765 .- 1552-9924. ; 127:6
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Between 2013 and 2015, concentrations of poly- and perfluoroalkyl substances (PFAS) in public drinking water supplies serving at least six million individuals exceeded the level set forth in the health advisory established by the U.S. Environmental Protection Agency. Other than data reported for contaminated sites, no systematic or prospective data exist on the relative source contribution (RSC) of drinking water to human PFAS exposures.OBJECTIVES: This study estimates the RSC of tap water to overall PFAS exposure among members of the general U.S.POPULATION:METHODS: We measured concentrations of 15 PFAS in home tap water samples collected in 1989-1990 from 225 participants in a nationwide prospective cohort of U.S. women: the Nurses' Health Study (NHS). We used a one-compartment toxicokinetic model to estimate plasma concentrations corresponding to tap water intake of PFAS. We compared modeled results with measured plasma PFAS concentrations among a subset of 110 NHS participants.RESULTS: Tap water perfluorooctanoic acid (PFOA) and perfluorononanoic acid (PFNA) were statistically significant predictors of plasma concentrations among individuals who consumed [Formula: see text] cups of tap water per day. Modeled median contributions of tap water to measured plasma concentrations were: PFOA 12% (95% probability interval 11%-14%), PFNA 13% (8.7%-21%), linear perfluorooctanesulfonic acid (nPFOS) 2.2% (2.0%-2.5%), branched perfluorooctanesulfonic acid (brPFOS) 3.0% (2.5%-3.2%), and perfluorohexanesulfonic acid (PFHxS) 34% (29%-39%). In five locations, comparisons of PFASs in community tap water collected in the period 2013-2016 with samples from 1989-1990 indicated increases in quantifiable PFAS and extractable organic fluorine (a proxy for unquantified PFAS).CONCLUSIONS: Our results for 1989-1990 compare well with the default RSC of 20% used in risk assessments for legacy PFAS by many agencies. Future evaluation of drinking water exposures should incorporate emerging PFAS.
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| 4. |
- Schultes, Lara, 1989-
(författare)
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Fluorine mass balance in wildlife and consumer products : How much organofluorine are we missing?
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Per- and polyfluoroalkyl substances (PFASs) are a class of anthropogenic pollutants. Many PFASs are highly persistent and have been linked to adverse effects in humans. According to latest estimates, there are more than 4700 PFASs in global commerce, which poses immense challenges for environmental monitoring. This thesis aims at the development, validation and application of total fluorine (TF) and extractable organic fluorine (EOF) methods to consumer products and wildlife in order to estimate the fraction of unidentified organic fluorine in these samples via fluorine mass balance calculations.Fluoropolymer-coated food packaging materials and reference materials were used in paper I to validate and compare the performance of three different TF methods. Combustion ion chromatography (CIC), particle-induced gamma ray emission spectroscopy (PIGE) and instrumental neutron activation analysis (INAA) revealed excellent analytical agreement and precision under most circumstances. PIGE and INAA had the advantage of being non-destructive, while CIC was favored due to low detection limits. Fluorine mass balance experiments indicated large amounts of unidentified EOF and non-extractable fluorine. Paper II investigated the occurrence of PFASs, EOF and TF in cosmetic products from the Swedish market. In addition to extremely high concentrations (up to 470 µg/g) of polyfluoroalkyl phosphate diesters (diPAPs; perfluoroalkyl acid (PFAA) precursors), unintentionally-added PFAAs were found in a number of products, together with large amounts of unidentified organic fluorine. Human exposure estimates for perfluorooctanoate (PFOA) using the latest dermal uptake coefficients revealed that PFAA exposure via cosmetics may be significant. Paper III evaluated time trends of PFASs, EOF and TF in Baltic cod (Gadus morhua) from 1981 to 2013. Increasing trends were observed for the predominant PFAS perfluorooctane sulfonate (PFOS), as well as for C9-C12 perfluoroalkyl carboxylic acids (PFCAs) at rates of up to 7.7% per year. Declining concentrations were detected for the PFOS precursor perfluorooctane sulfonamide (FOSA), the EOF and its fraction not accounted for by target PFASs, while TF did not show any significant trends. The increasing concentrations of PFAAs despite their production phase-out could be attributed to either direct exposure of cod to legacy PFAAs or to indirect exposure via PFAA-precursor metabolism. Furthermore, negative correlations of certain PFASs with liver somatic index and body length were observed, which play an important role in the under-standing of toxicological effects of PFASs on wildlife. Paper IV studied the distribution of PFASs, EOF and TF in tissues from a Greenland killer whale (Orcinus orca). The sum of target PFAS concentrations was highest in liver (339 ng/g) and lowest in blubber (9.4 ng/g), consistent with other tissue distribution studies in marine mammals. In contrast, TF and EOF concentrations were highest in blubber (1315 and 229 ng/g, respectively), suggesting the presence of high concentrations of one or more presently unidentified fluorinated compounds. With the help of high resolution mass spectrometry-based suspect screening, several PFAS homologue series and individual PFASs not included in target analysis were detected.
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| 5. |
- Soerensen, Anne L., et al.
(författare)
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A mass budget for mercury and methylmercury in the Arctic Ocean
- 2016
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Ingår i: Global Biogeochemical Cycles. - 0886-6236 .- 1944-9224. ; 30:4, s. 560-575
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Tidskriftsartikel (refereegranskat)abstract
- Elevated biological concentrations of methylmercury (MeHg), a bioaccumulative neurotoxin, are observed throughout the Arctic Ocean, but major sources and degradation pathways in seawater are not well understood. We develop a mass budget for mercury species in the Arctic Ocean based on available data since 2004 and discuss implications and uncertainties. Our calculations show that high total mercury (Hg) in Arctic seawater relative to other basins reflect large freshwater inputs and sea ice cover that inhibits losses through evasion. We find that most net MeHg production (20Mga(-1)) occurs in the subsurface ocean (20-200m). There it is converted to dimethylmercury (Me2Hg: 17Mga(-1)), which diffuses to the polar mixed layer and evades to the atmosphere (14Mga(-1)). Me2Hg has a short atmospheric lifetime and rapidly degrades back to MeHg. We postulate that most evaded Me2Hg is redeposited as MeHg and that atmospheric deposition is the largest net MeHg source (8Mga(-1)) to the biologically productive surface ocean. MeHg concentrations in Arctic Ocean seawater are elevated compared to lower latitudes. Riverine MeHg inputs account for approximately 15% of inputs to the surface ocean (2.5Mga(-1)) but greater importance in the future is likely given increasing freshwater discharges and permafrost melt. This may offset potential declines driven by increasing evasion from ice-free surface waters. Geochemical model simulations illustrate that for the most biologically relevant regions of the ocean, regulatory actions that decrease Hg inputs have the capacity to rapidly affect aquatic Hg concentrations.
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| 6. |
- Yeung, Leo W. Y., 1981-, et al.
(författare)
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Vertical Profiles, Sources, and Transport of PFASs in the Arctic Ocean
- 2017
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 51:12, s. 6735-6744
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Tidskriftsartikel (refereegranskat)abstract
- The relative importance of atmospheric versus oceanic transport for poly- and perfluorinated alkyl substances (PFASs) reaching the Arctic Ocean is not well understood. Vertical profiles from the Central Arctic Ocean and shelf water, snow and meltwater samples were collected in 2012; 13 PFASs (C6-C12 PFCAs; C6, 8, 10 PFSAs; MeFOSAA and EtFOSAA; and FOSA) were routinely detected (range: <5-343 pg/L). PFASs were only detectable above 150 m depth in the polar mixed layer (PML) and halocline. Enhanced concentrations were observed in snow and meltpond samples, implying atmospheric deposition as an important source of PFASs. Model results suggested atmospheric inputs to account for 34-59% (∼11-19 pg/L) of measured PFOA concentrations in the PML (mean 32 ± 15 pg/L). Modeled surface and halocline measurements for PFOS based on North Atlantic inflow (11-36 pg/L) agreed with measurements (mean, 17, range <5-41 pg/L). Modeled deep water concentrations below 200 m (5-15 pg/L) were slightly higher than measurements (<5 pg/L), suggesting the lower bound of PFAS emissions estimates from wastewater and rivers may provide the best estimate of inputs to the Arctic. Despite low concentrations in deep water, this reservoir is expected to contain most of the PFOS mass in the Arctic (63-180 Mg) and is projected to continue increasing to 2038.
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| 7. |
- Zhang, Yanxu, et al.
(författare)
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A Global Model for Methylmercury Formation and Uptake at the Base of Marine Food Webs
- 2020
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Ingår i: Global Biogeochemical Cycles. - 0886-6236 .- 1944-9224. ; 34:2
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Tidskriftsartikel (refereegranskat)abstract
- Monomethylmercury (CH3Hg) is the only form of mercury (Hg) known to biomagnify in food webs. Here we investigate factors driving methylated mercury [MeHg = CH3Hg + (CH3)(2)Hg)] production and degradation across the global ocean and uptake and trophic transfer at the base of marine food webs. We develop a new global 3-D simulation of MeHg in seawater and phyto/zooplankton within the Massachusetts Institute of Technology general circulation model. We find that high modeled MeHg concentrations in polar regions are driven by reduced demethylation due to lower solar radiation and colder temperatures. In the eastern tropical subsurface waters of the Atlantic and Pacific Oceans, the model results suggest that high MeHg concentrations are associated with enhanced microbial activity and atmospheric inputs of inorganic Hg. Global budget analysis indicates that upward advection/diffusion from subsurface ocean provides 17% of MeHg in the surface ocean. Modeled open ocean phytoplankton concentrations are relatively uniform because lowest modeled seawater MeHg concentrations occur in oligotrophic regions with the smallest size classes of phytoplankton, with relatively high uptake of MeHg and vice versa. Diatoms and synechococcus are the two most important phytoplankton categories for transferring MeHg from seawater to herbivorous zooplankton, contributing 35% and 25%, respectively. Modeled ratios of MeHg concentrations between herbivorous zooplankton and phytoplankton are 0.74-0.78 for picoplankton (i.e., no biomagnification) and 2.6-4.5 for eukaryotic phytoplankton. The spatial distribution of the trophic magnification factor is largely determined by the zooplankton concentrations. Changing ocean biogeochemistry resulting from climate change is expected to have a significant impact on marine MeHg formation and bioaccumulation.
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