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  • 1. Harner, Tom
    et al.
    Rauert, Cassandra
    Muir, Derek
    Schuster, Jasmin K.
    Hsu, Yu-Mei
    Zhang, Leiming
    Marson, George
    Watson, John G.
    Ahad, Jason
    Cho, Sunny
    Jariyasopit, Narumol
    Kirk, Jane
    Korosi, Jennifer
    Landis, Matthew S.
    Martin, Jonathan W.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Stockholm University, Science for Life Laboratory (SciLifeLab). University of Alberta, Canada.
    Zhang, Yifeng
    Fernie, Kim
    Wentworth, Gregory R.
    Wnorowski, Andrzej
    Dabek, Ewa
    Charland, Jean-Pierre
    Pauli, Bruce
    Wania, Frank
    Galarneau, Elisabeth
    Cheng, Irene
    Makar, Paul
    Whaley, Cynthia
    Chow, Judith C.
    Wang, Xiaoliang
    Air synthesis review: polycyclic aromatic compounds in the oil sands region2018In: Environmental Reviews, ISSN 1181-8700, E-ISSN 1208-6053, Vol. 26, no 4, p. 430-468Article, review/survey (Refereed)
    Abstract [en]

    This air synthesis review presents the current state of knowledge on the sources, fates, and effects for polycyclic aromatic compounds (PACs) and related chemicals released to air in the oil sands region (OSR) in Alberta, Canada. Through the implementation of the Joint Canada-Alberta Oil Sands Monitoring Program in 2012 a vast amount of new information on PACs has been acquired through directed monitoring and research projects and reported to the scientific community and public. This new knowledge addresses questions related to cumulative effects and informs the sustainable management of the oil sands resource while helping to identify gaps in understanding and priorities for future work. As a result of this air synthesis review on PACs, the following topics have been identified as new science priorities: (i) improving emissions reporting to better account for fugitive mining emissions of PACs that includes a broader range of PACs beyond the conventional polycyclic aromatic hydrocarbons (PAHs) including, inter alia, alkylated-PAHs (alk-PAHs), dibenzothiophene (DBT), alk-DBTs, nitro-PAHs, oxy-PAHs including quinones and thia-and aza-arenes; (ii) improving information on the ambient concentrations, long-range transport, and atmospheric deposition of these broader classes of PACs and their release (with co-contaminants) from different types of mining activities; (iii) further optimizing electricity-free and cost-effective approaches for assessing PAC deposition (e.g., snow sampling, lichens, passive ambient sampling) spatially across the OSR and downwind regions; (iv) designing projects that integrate monitoring efforts with source attribution models and ecosystem health studies to improve understanding of sources, receptors, and effects; (v) further optimizing natural deposition archives (e.g., sediment, peat, tree rings) and advanced forensic techniques (e.g., isotope analysis, marker compounds) to provide better understanding of sources of PACs in the OSR over space and time; (vi) conducting process research to improve model capabilities for simulating atmospheric chemistry of PACs and assessing exposure to wildlife and humans; and (vii) developing tools and integrated strategies for assessing cumulative risk to wildlife and humans by accounting for the toxicity of the mixture of chemicals in air rather than on a single compound basis.

  • 2. Land, Magnus
    et al.
    de Wit, Cynthia A.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Bignert, Anders
    Cousins, Ian T.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Herzke, Dorte
    Johansson, Jana H.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Martin, Jonathan W.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. University of Alberta, Canada.
    What is the effect of phasing out long-chain per- and polyfluoroalkyl substances on the concentrations of perfluoroalkyl acids and their precursors in the environment? A systematic review2018In: Environmental Evidence, ISSN 2047-2382, E-ISSN 2047-2382, Vol. 7, no 1, article id UNSP 4Article, review/survey (Refereed)
    Abstract [en]

    Background: There is a concern that continued emissions of man-made per-and polyfluoroalkyl substances (PFASs) may cause environmental and human health effects. Now widespread in human populations and in the environment, several PFASs are also present in remote regions of the world, but the environmental transport and fate of PFASs are not well understood. Phasing out the manufacture of some types of PFASs started in 2000 and further regulatory and voluntary actions have followed. The objective of this review is to understand the effects of these actions on global scale PFAS concentrations. Methods: Searches for primary research studies reporting on temporal variations of PFAS concentrations were performed in bibliographic databases, on the internet, through stakeholder contacts and in review bibliographies. No time, document type, language or geographical constraints were applied in the searches. Relevant subjects included human and environmental samples. Two authors screened all retrieved articles. Dual screening of 10% of the articles was performed at title/abstract and full-text levels by all authors. Kappa tests were used to test consistency. Relevant articles were critically appraised by four reviewers, with double checking of 20% of the articles by a second reviewer. Meta-analysis of included temporal trends was considered but judged to not be appropriate. The trends were therefore discussed in a narrative synthesis. Results: Available evidence suggests that human concentrations of perfluorooctane sulfonate (PFOS), perfluorodecane sulfonate (PFDS), and perfluorooctanoic acid (PFOA) generally are declining, while previously increasing concentrations of perfluorohexane sulfonate (PFHxS) have begun to level off. Rapid declines for PFOS-precursors (e.g. perfluorooctane sulfonamide, FOSA) have also been consistently observed in human studies. In contrast, limited data indicate that human concentrations of PFOS and PFOA are increasing in China where the production of these substances has increased. Human concentrations of longer-chained perfluoroalkyl carboxylic acids (PFCAs) with 9-14 carbon atoms are generally increasing or show insignificant trends with too low power to detect a trend. For abiotic and biological environmental samples there are no clear patterns of declining trends. Most substances show mixed results, and a majority of the trends are insignificant with low power to detect a trend. Conclusions: For electrochemically derived PFASs, including PFOS and PFOA, most human studies in North America and Europe show consistent statistically significant declines. This contrasts with findings in wildlife and in abiotic environmental samples, suggesting that declining PFOS, PFOS-precursor and PFOA concentrations in humans likely resulted from removal of certain PFASs from commercial products including paper and board used in food packaging. Increasing concentrations of long-chain PFCAs in most matrices, and in most regions, is likely due to increased use of alternative PFASs. Continued temporal trend monitoring in the environment with well-designed studies with high statistical power are necessary to evaluate the effectiveness of past and continuing regulatory mitigation measures. For humans, more temporal trend studies are needed in regions where manufacturing is most intense, as the one human study available in China is much different than in North America or Europe.

  • 3. Liu, Jiaying
    et al.
    Martin, Jonathan W.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. University of Alberta, Canada.
    Comparison of Bisphenol A and Bisphenol S Percutaneous Absorption and Biotransformation2019In: Journal of Environmental Health Perspectives, ISSN 0091-6765, E-ISSN 1552-9924, Vol. 127, no 6, article id 067008Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Bisphenol S (BPS) has been widely substituted for bisphenol A (BPA) on thermal papers, but little is known about its skin absorption.

    OBJECTIVES: We compared the percutaneous absorption and biotransformation of BPS and BPA in vitro and in a controlled human trial.

    METHODS: Absorption and biotransformation of BPS and BPA were monitored across reconstructed human epidermis at two environmentally relevant doses over 25 h. In the human trial, five male participants handled thermal receipts containing BPS and washed their hands after 2 h. Urine (0-48 h) and serum (0-7.5h) were analyzed for target bisphenols, and one participant repeated the experiment with extended monitoring. BPS data were compared with published data for isotope-labeled BPA (BPA-d(16)) in the same participants.

    RESULTS: At doses of 1.5 and 7.7 mu g/cm(2) applied to reconstructed human epidermis, the permeability coefficient of BPS (0.009 and 0.003 cm/h, respectively) was significantly lower than for BPA (0.036 and 0.033 cm/h, respectively), and metabolism of both bisphenols was negligible. In participants handling thermal receipts, the quantities of BPS and BPA-d(1)(6) on hands was significantly correlated with maximum urinary event flux (lag), but the slope was lower for BPS than BPA (beta=0.12 and 1.1, respectively). As a proportion of total urinary bisphenol, free BPS [mean +/- standard deviation (SD): 6.9 +/- 2.8%] was higher than for free BPA (2.7 +/- 1.9%). Postexposure maximum urinary BPS concentrations (0.93 to 3.0 ng/mL; n = 5) were in the 93-98th percentile range of BPS in background Canadians (0.91-3.2 ng/mL; n =467).

    CONCLUSION: Both the in vitro and human studies suggested lower percutaneous absorption of BPS compared with BPA, but a lower biotransformation efficiency of BPS should also be considered in its evaluation as a BPA substitute.

  • 4. Liu, Jiaying
    et al.
    Martin, Jonathan W.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. University of Alberta, Canada.
    Prolonged Exposure to Bisphenol A from Single Dermal Contact Events2017In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 51, no 17, p. 9940-9949Article in journal (Refereed)
    Abstract [en]

    Bisphenol A (BPA) is an endocrine disruptor frequently detected in human biofluids. Dermal absorption of BPA from thermal paper receipts occurs but BPA pharmacokinetics following dermal exposure is not understood. To compare the pharmacokinetics of dermal and dietary BPA exposure, six male participants handled simulated receipts containing relevant levels of BPA (isotope-labeled BPA-d(16)) for 5 min, followed by hand-washing 2 h later. Urine (0-48 h) and serum (0-7.5 h) were monitored for free and total BPA-d16. One week later, participants returned for a dietary administration with monitoring as above. One participant repeated the dermal administration with extended monitoring of urine (9 days) and serum (2 days). After dietary exposure, urine total BPA-d16 peaked within 5 h and quickly cleared within 24 h. After dermal exposure, cumulative excretion increased linearly for 2 days, and half the participants still had detectable urinary total BPA-d(16) after 1 week. The participant repeating the dermal exposure had detectable BPA-d(16) in urine for 9 days, showed linear cumulative excretion over 5 days, and had detectable free BPA-d(16) in serum. Proportions of free BPA-d(16) in urine following dermal exposure (0.71%-8.3% of total BPA-d(16)) were generally higher than following the dietary exposure (0.29%-1.4%). Compared to dietary BPA exposure, dermal absorption of BPA leads to prolonged exposure and may lead to higher proportions of unconjugated BPA in systemic circulation.

  • 5. Liu, Jiaying
    et al.
    Wattar, Nour
    Field, Catherine J.
    Dinu, Irina
    Dewey, Deborah
    Martin, Jonathan W.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. University of Alberta, Canada.
    Exposure and dietary sources of bisphenol A (BPA) and BPA-alternatives among mothers in the APrON cohort study2018In: Environment International, ISSN 0160-4120, E-ISSN 1873-6750, Vol. 119, p. 319-326Article in journal (Refereed)
    Abstract [en]

    Diet is regarded as the main source of bisphenol A (BPA) exposure, but comparatively little is known about dietary sources of BPA-alternatives. Here we measured exposure of BPA and BPA-alternatives among pregnant women in Canada, estimated their 24-h intakes and examined the importance of various dietary sources. Free and total BPA, bisphenol S (BPS) and bisphenol F (BPF) were measured in 467 second trimester maternal urine samples, and in 455 paired samples collected M three months postpartum. Linear regression was used to evaluate associations between urinary concentrations of bisphenols and 24-h dietary recall data. The geometric means of total BPA in second trimester and postpartum urine (1.2 and 0.95 ng/mL, respectively) were 5-7 times higher than corresponding total BPS (0.16 and 0.17 ng/mL). The detection frequency of BPF was only 9% (i.e. > 1.0 ng/mL). However, M both time points 95th percentiles of total BPF (7.3 and 4.2 ng/mL, respectively) were similar to total BPA (8.2 and 5.0 ng/mL). Free BPS and BPF were detected in < 2% of samples, but were detectable when total BPS or BPF concentrations were highest, always M < 1% of the total concentration. The tolerable daily intake for total BPA (i.e. 18 nmol/kg BW/d) was not exceeded, but for BPS the estimated 24-h intake was as high as 14 nmol/kg BW/d (95th percentile: 0.12 nmol/kg BW/d), and for BPF was even higher among the highest centile of exposure (maximum and 95th percentile: 30, 0.81 nmol/kg BW/d). Canned food consumption was associated with higher total BPA, but was not associated with BPS. For BPF, mustard consumption may be an important exposure source, particularly among the highest exposed. Relatively high exposure to BPS and BPF in a minority of pregnant women highlights the need to better understand the associated health risks and exposure sources of BPA-alternatives.

  • 6. Liu, Yanna
    et al.
    Qian, Manli
    Ma, Xinxin
    Zhu, Lingyan
    Martin, Jonathan W.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Stockholm University, Science for Life Laboratory (SciLifeLab). University of Alberta, Canada.
    Nontarget Mass Spectrometry Reveals New Perfluoroalkyl Substances in Fish from the Yangtze River and Tangxun Lake, China2018In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 52, no 10, p. 5830-5840Article in journal (Refereed)
    Abstract [en]

    Nontarget high-resolution mass spectrometry (Nt-HRMS) has been proven useful for the identification of unknown poly- and perfluoroalkyl substances (PFASs) in commercial products and water, but applications to biological samples are limited. China is the major PFAS-manufacturing nation; thus, here, we adapted our Nt-HRMS methods to fish collected from the Yangtze River and Tangxun Lake to discover potentially bioaccumulative PFASs in aquatic organisms destined for human consumption. In addition to traditional PFASs, over 330 other fluorinated analytes belonging to 10 classes of PFASs were detected among the pooled fish livers, including 6 sulfonate classes, 2 amine classes, 1 carboxylate class, and 1 N-heterocycle class. One class was detected in samples from both locations, 8 classes were detected exclusively in Tangxun Lake fish, and 1 class was detected exclusively in Yangtze River fish, 10 km downstream of a fluorochemical manufacturing site where we first reported these substances in wastewater 3 years ago. Overall, 4 of the PFAS classes (>165 analytes) are reported for the first time here. Wider monitoring and toxicological testing should be a priority for understanding the health risks posed to people and wildlife exposed to these substances.

  • 7. Liu, Yanna
    et al.
    Richardson, Evan S.
    Derocher, Andrew E.
    Lunn, Nicholas J.
    Lehmler, Hans-Joachim
    Li, Xueshu
    Zhang, Yifeng
    Cui, Julia Yue
    Cheng, Lihua
    Martin, Jonathan W.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Stockholm University, Science for Life Laboratory (SciLifeLab). University of Alberta, Canada.
    Hundreds of Unrecognized Halogenated Contaminants Discovered in Polar Bear Serum2018In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 57, no 50, p. 16401-16406Article in journal (Refereed)
    Abstract [en]

    Exposure of polar bears (Ursus maritimus) to persistent organic pollutants was discovered in the 1970s, but recent evidence suggests the presence of unknown toxic chemicals in their blood. Protein and phospholipid depleted serum was stirred with polyethersulfone capillaries to extract a broad range of analytes, and nontarget mass spectrometry with fragmentation flagging was used for detection. Hundreds of analytes were discovered belonging to 13 classes, including novel polychlorinated biphenyl (PCB) metabolites and many fluorinated or chlorinated substances not previously detected. All analytes were detected in the oldest (mid-1980s) archived polar bear serum from Hudson Bay and Beaufort Sea, and all fluorinated classes showed increasing trends. A mouse experiment confirmed the novel PCB metabolites, suggesting that these could be widespread in mammals. Historical exposure and toxic risk has been underestimated, and these halogenated contaminants pose uncertain risks to this threatened species.

  • 8. Morandi, Garrett D.
    et al.
    Wiseman, Steve B.
    Guan, Miao
    Zhang, Xiaowei W.
    Martin, Jonathan W.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. University of Alberta, Canada.
    Giesy, John P.
    Elucidating mechanisms of toxic action of dissolved organic chemicals in oil sands process-affected water (OSPW)2017In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 186, p. 893-900Article in journal (Refereed)
    Abstract [en]

    Oil sands process-affected water (OSPW) is generated during extraction of bitumen in the surface-mining oil sands industry in Alberta, Canada, and is acutely and chronically toxic to aquatic organisms. It is known that dissolved organic compounds in OSPW are responsible for most toxic effects, but knowledge of the specific mechanism(s) of toxicity, is limited. Using bioassay-based effects-directed analysis, the dissolved organic fraction of OSPW has previously been fractionated, ultimately producing refined samples of dissolved organic chemicals in OSPW, each with distinct chemical profiles. Using the Escherichia coli K-12 strain MG1655 gene reporter live cell array, the present study investigated relationships between toxic potencies of each fraction, expression of genes and characterization of chemicals in each of five acutely toxic and one non-toxic extract of OSPW derived by use of effects-directed analysis. Effects on expressions of genes related to response to oxidative stress, protein stress and DNA damage were indicative of exposure to acutely toxic extracts of OSPW. Additionally, six genes were uniquely responsive to acutely toxic extracts of OSPW. Evidence presented supports a role for sulphur- and nitrogen-containing chemical classes in the toxicity of extracts of OSPW.

  • 9. Nyanza, Elias C.
    et al.
    Bernier, Francois P.
    Manyama, Mange
    Hatfield, Jennifer
    Martin, Jonathan W.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Stockholm University, Science for Life Laboratory (SciLifeLab).
    Dewey, Deborah
    Maternal exposure to arsenic and mercury in small-scale gold mining areas of Northern Tanzania2019In: Environmental Research, ISSN 0013-9351, E-ISSN 1096-0953, Vol. 173, p. 432-442Article in journal (Refereed)
    Abstract [en]

    Artisanal and small-scale gold mining (ASGM) in Tanzania results in occupational exposures and environmental contamination to toxic chemical elements such as arsenic and mercury. Populations living in such areas may be exposed by various routes, and prenatal exposure to arsenic and mercury has been associated with adverse birth outcomes and developmental delays. The aim of this study was to determine if levels of arsenic and mercury differed among pregnant women living in areas with and without ASGM activities in Northern Tanzania. This cross-sectional study is part of the ongoing Mining and Health prospective longitudinal study. Spot urine samples and dried blood spots were collected at the antenatal health clinics from pregnant women (n = 1056) at 16-27 weeks gestation. Urine samples were analyzed for total arsenic (T-As) and dried blood spots were analyzed for total mercury (T-Hg). Women in the ASGM cohort had median T-As levels (9.4 mu g/L; IQR: 4.9-15.1) and T-Hg levels (1.2 mu g/L; IQR: 0.8-1.86) that were significantly higher than the median T-As levels (6.28 mu g/L; IQR: 3.7-14.1) and T-Hg levels (0.66 mu g/L; IQR: 0.3-1.2) of women in the non-ASGM cohort (Mann-Whitney U test, T-As: z = - 9.881, p = 0.0005; T-Hg: z = - 3.502, p < 0.0001). Among pregnant women from ASGM areas, 25% had urinary T-As and 75% had blood T-Hg above the established human biomonitoring reference values of 15 and 0.80 mu g/L. In the ASGM cohort, lower maternal education and low socioeconomic status increased the odds of higher T-As levels by 20% (p < 0.05) and 10% (p < 0.05), respectively. Women involved in mining activities and those of low socioeconomic status had increased odds of higher T-Hg by 70% (p < 0.001) and 10% (p < 0.05), respectively. Arsenic and mercury concentrations among women in non-ASGM areas suggest exposure sources beyond ASGM activities that need to be identified. Arsenic and mercury levels in women in Tanzania are of public health concern and their association with adverse birth and child developmental outcomes will be examined in future studies on this cohort.

  • 10. Nyanza, Elias C.
    et al.
    Dewey, Deborah
    Bernier, Francois
    Manyama, Mange
    Hatfield, Jennifer
    Martin, Jonathan W.
    Stockholm University, Science for Life Laboratory (SciLifeLab). Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Validation of Dried Blood Spots for Maternal Biomonitoring of Nonessential Elements in an Artisanal and Small-Scale Gold Mining Area of Tanzania2019In: Environmental Toxicology and Chemistry, ISSN 0730-7268, E-ISSN 1552-8618, Vol. 38, no 6, p. 1285-1293Article in journal (Refereed)
    Abstract [en]

    Biomonitoring studies of vulnerable populations in low- and middle-income countries are limited because traditional sampling methods are challenging to implement in low-resource settings. The present study examined the feasibility, precision, and accuracy of dried blood spots (DBS) for human biomonitoring of nonessential elements (cadmium [Cd], mercury [Hg], and lead [Pb]) in an area of northern Tanzania with artisanal and small-scale gold mining activities. Pregnant women (n = 44) were recruited in Geita during antenatal clinic visits, and DBS from capillary blood were collected on filter paper. As a gold-standard comparison, venous blood was sampled from the same participants and compared with the DBS. Venous blood, DBS, and quality control samples were analyzed for chemical elements by inductively coupled plasma mass spectrometry. Field blanks were very clean for most elements, generally only twice as high as corresponding laboratory filter blanks. No significant differences were found between duplicate DBS samples taken from the same participants, with near perfect intraclass correlation coefficients (0.99) for Cd, Hg, and Pb, indicating excellent reliability. Moreover, correlation was strong (r(2) > 0.9) and significant (p < 0.0001) between DBS and the quantitative venous blood, with regression line slopes close to 1.0 (0.847, 0.976, and 0.969 for Cd, Hg, and Pb, respectively), indicating high accuracy of the DBS method compared with the gold-standard approach. The DBS method is minimally invasive and was a feasible, precise, and accurate means of measuring exposure to Cd, Hg, and Pb in pregnant women in a low-resource setting. 

  • 11. Reardon, Anthony J. F.
    et al.
    Karathra, Jacqueline
    Ribbenstedt, Anton
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Benskin, Jonathan P.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    MacDonald, Amy M.
    Kinniburgh, David W.
    Hamilton, Trevor J.
    Fouad, Karim
    Martin, Jonathan W.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. University of Alberta, Canada.
    Neurodevelopmental and Metabolomic Responses from Prenatal Coexposure to Perfluorooctanesulfonate (PFOS) and Methylmercury (MeHg) in Sprague-Dawley Rats2019In: Chemical Research in Toxicology, ISSN 0893-228X, E-ISSN 1520-5010, Vol. 32, no 8, p. 1656-1669Article in journal (Refereed)
    Abstract [en]

    Methylmercury (MeHg) and perfluoro-octanesulfonate (PFOS) are major contaminants of human blood that are both common in dietary fish, thereby raising questions about their combined impact on human development. Here, pregnant Sprague-Dawley rats ingested a daily dose, from gestational day 1 through to weaning, of either 1 mg/kg bw PFOS (PFOS-only), 1 mg/kg MeHg (MeHg-only), a mixture of 0.1 mg/kg PFOS and 1 mg/kg MeHg (Low-Mix), or of 1 mg/kg of PFOS and 1 mg/kg MeHg (High-Mix). Newborns were monitored for physical milestones and reflexive developmental responses, and in juveniles the spontaneous activity, anxiety, memory, and cognition were assessed. Targeted metabolomics of 199 analytes was applied to sectioned brain regions of juvenile offspring. Newborns in the High-Mix group had decreased weight gain as well as delayed reflexes and innate behavioral responses compared to controls and individual chemical groups indicating a toxicological interaction on early development. In juveniles, cumulative mixture effects increased in a dose-dependent manner in tests of anxiety-like behavior. However, other developmental test results suggested antagonism, as PFOS-only and MeHg-only juveniles had increased hyperactivity and thigmotaxic behavior, respectively, but fewer effects in Low-Mix and High-Mix groups. Consistent with these behavioral observations, a pattern of antagonism was also observed in neurochemicals measured in rat cortex, as PFOS-only and MeHg-only juveniles had altered concentrations of metabolites (e.g., lipids, amino acids, and biogenic amines), while no changes were evident in the combined exposures. The cortical metabolites altered in PFOS-only and MeHg-only exposed groups are involved in inhibitory and excitatory neurotransmission. These proof-of-principle findings at relatively high doses indicate the potential for toxicological interaction between PFOS and MeHg, with developmental-stage specific effects. Future mixture studies at lower doses are warranted, and prospective human birth cohorts should consider possible confounding effects from PFOS and mercury exposure on neurodevelopment.

  • 12. Reardon, Anthony J. F.
    et al.
    Moez, Elham Khodayari
    Dinu, Irina
    Goruk, Susan
    Field, Catherine J.
    Kinniburgh, David W.
    MacDonald, Amy M.
    Martin, Jonathan W.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. University of Alberta, Canada.
    Longitudinal analysis reveals early-pregnancy associations between perfluoroalkyl sulfonates and thyroid hormone status in a Canadian prospective birth cohort2019In: Environment International, ISSN 0160-4120, E-ISSN 1873-6750, Vol. 129, p. 389-399Article in journal (Refereed)
    Abstract [en]

    Serum perfluoroalkyl acids (PFAAs) have been linked to disruption of maternal thyroid hormone homeostasis, but results have varied between studies which we hypothesized was due to timing of the thyroid hormone measurements, variability in PFAA isomer patterns, or presence of other stressors. In a longitudinal study design, we investigated the time-dependency of associations between PFAA isomers and thyroid hormones during pregnancy and post-partum while considering thyroid peroxidase antibody (TPOAb) status and mercury (Hg) co-exposure. In participants of a prospective Canadian birth cohort (n = 494), free thyroxine (FT4), free triiodothyronine (FT3), thyroid stimulating hormone (TSH) and TPOAb were quantified in maternal plasma collected in each trimester and 3-months postpartum, and 25 PFAAs (15 linear and 10 branched) and Hg were quantified in samples collected during the second trimester. Perfluorohexane sulfonate (PFHxS) and total branched isomers of perfluorooctane sulfonate (PFOS) were positively associated with TSH in mixed-effect models, with strongest associations early in gestation. Throughout pregnancy and post-partum, PFHxS was inversely associated with FT4, consistent with elevated TSH, while Hg was inversely associated with FT3. In TPOAb-positive women, negative associations were found between PFUnA and FT4, and 1m-PFOS and TSH, supporting previous studies that thyroid disorder could increase susceptibility to PFAA-mediated hormone dysregulation. Hg did not confound associations but was a significant interaction term, revealing further positive associations between PFOS isomers (Sigma 3m + 4m-PFOS) and TSH. Higher perfluoroalkyl sulfonate exposures were associated with higher TSH and/or lower FT4, strongly suggestive that PFHxS and branched PFOS isomers are risk factors for subclinical maternal hypothyroidism. Isomer-specific analysis is important in future studies, as crude measures of 'totalPFOS' masked the associations of branched isomers. A concerning result was for PFHxS which had consistent negative associations with FT4 at all time points and a positive association with TSH in early pregnancy when fetal development is most sensitive to disruption.

  • 13. Zhong, Cheng
    et al.
    Li, Jiaying
    Flynn, Shannon L.
    Nesbø, Camilla L.
    Sun, Chenxing
    von Gunten, Konstantin
    Lanoil, Brian D.
    Goss, Greg G.
    Martin, Jonathan W.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. University of Alberta, Canada.
    Alessi, Daniel S.
    Temporal Changes in Microbial Community Composition and Geochemistry in Flowback and Produced Water from the Duvernay Formation2019In: Acs Earth and Space Chemistry, ISSN 2472-3452, Vol. 3, no 6, p. 1047-1057Article in journal (Refereed)
    Abstract [en]

    Microbial activity in flowback and produced water (FPW) may negatively influence shale oil and gas extraction. However, the impacts of using recycled produced water (RPW) for subsequent fracturing jobs are not well-understood. In this study, we compared time series of FPW samples from two horizontally fractured wells drilled into the Duvernay Formation in Alberta, Canada; well 1 used RPW in the makeup of the hydraulic fracturing fluid (HFF) whereas well 2 did not. 16S rRNA gene sequencing and live/dead cell enumeration were used to track microbial communities. Within 20 days of flowback, total dissolved solids in well 1 and well 2 increased from 5310 mg/L and 288 mg/L to over 150,000 mg/L, and FPW temperatures increased from 20 and 9 degrees C to 77 and 71 degrees C, respectively. Alkyl dimethyl benzyl ammonium chloride (biocide) in well 2 decreased from 25 mu g/L to below the detection limit of 0.5 mu g/L. Cellular biomass decreased from similar to 10(5) cells mL(-1) to less than the detection limit of 10(5) cells mL(-1) in both wells, and the community in the samples was initially diverse but rapidly shifted to become dominated by the sulfidogenic lineage Halanaerobium. Methanogens were detected at low relative abundance within archaea, with DNA concentrations in FPW after 20 days inadequate for sequencing. Comparing the two wells, the start time of Halanaerobium enrichment was considerably shortened in well 1 relative to well 2. Our results suggest that subsurface environmental parameters primarily drive the rapid enrichment of sulfidogenic and halotolerant bacteria and current recycling strategies can facilitate the growth of these bacteria, whereas biocide seems to be a less important factor in this shift.

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