ABSTRACT In the process of performing risk assessments for humans or animals, it has been shown t... more ABSTRACT In the process of performing risk assessments for humans or animals, it has been shown that the assumption that all of a contaminant in an ingested matrix poses risk is not always accurate. Specifically, not all of the contaminant is bioavailable (absorbed by the body). Bioaccessibility, which is the fraction of a contaminant that dissolves in gastrointestinal conditions, is used to estimate bioavailability. This is because in vitro laboratory extractions can be used, since they have the potential to be cost effective, commercially viable, and comparable to bioavailability measurements. Bioaccessibility extractions were developed from the fields of pharmaceutical dissolution testing, nutrition, and safety, based on simulated gastric and intestinal fluids developed for those applications. In the development of a number of different methods, some groups have focused on simple methods with few chemicals that can be easily conducted in a laboratory, and others have targeted maximum physiological representativeness with its accompanying complexity (e.g., dynamic systems and incorporation of microorganisms). Bioaccessibility of inorganic contaminants is most susceptible to changes in pH, and organic contaminant bioaccessibility is most affected by organic content of the extraction fluid. Validation of several methods, accomplished by finding significant relationships between bioaccessibility and bioavailability results, has been demonstrated for arsenic, lead, and cadmium, and comparisons for organic contaminants indicate that several methods are promising. Regulatory agencies should be able to develop frameworks that allow bioaccessibility extractions to be relevant for use in risk assessment.
As mercury emissions continue and climate-mediated permafrost thaw increases the burden of this c... more As mercury emissions continue and climate-mediated permafrost thaw increases the burden of this contaminant in northern waters, Inuit from a Northwest passage community in the Canadian Arctic Archipelago pressed for an assessment of their subsistence catches. Sea-run salmonids (n = 537) comprising Arctic char (Salvelinus alpinus), lake trout (S. namaycush), lake whitefish (Coregonus clupeaformis), and cisco (C. autumnalis, C. sardinella) were analyzed for muscle mercury. Methylmercury is a neurotoxin and bioaccumulated with fish age, but other factors including selenium and other elements, diet and trophic level as assessed by stable isotopes of nitrogen (δ15N) and carbon (δ13C), as well as growth rate, condition, and geographic origin, also contributed depending on the species, even though all the fish shared a similar anadromous or sea-run life history. Although mean mercury concentrations for most of the species were ~0.09 µg·g−1 wet weight (ww), below the levels described in sev...
The identification of food fish bearing anthropogenic contaminants is one of many priorities for ... more The identification of food fish bearing anthropogenic contaminants is one of many priorities for Indigenous peoples living in the Arctic. Mercury (Hg), arsenic (As), and persistent organic pollutants including polychlorinated biphenyls (PCBs) are of concern, and these are reported, in some cases for the first time, for fish sampled in and around King William Island, located in Nunavut, Canada. More than 500 salmonids, comprising Arctic char, lake trout, lake whitefish, and ciscoes, were assayed for contaminants. The studied species are anadromous, migrating to the ocean to feed in the summers and returning to freshwater before sea ice formation in the autumn. Assessments of muscle Hg levels in salmonids from fishing sites on King William Island showed generally higher levels than from mainland sites, with mean concentrations generally below guidelines, except for lake trout. In contrast, mainland fish showed higher means for As, including non-toxic arsenobetaine, than island fish. L...
Versatile sample preparation platform for mixing, splitting and extraction on patterned surfaces ... more Versatile sample preparation platform for mixing, splitting and extraction on patterned surfaces and subsequent detection by a UV/vis smartphone spectrometer.
Assessing the extent to which emerging contaminants (ECs) such as perfluoroalkyl and polyfluoroal... more Assessing the extent to which emerging contaminants (ECs) such as perfluoroalkyl and polyfluoroalkyl substances (PFAS) have been released into the environment is one of the foundations for developing effective management and remediation strategies for impacted sites. PFAS are known to have caused the contamination of soil, groundwater, and surface water as a result of aqueous film forming foam (AFFF) being accidentally or intentionally released into the environment. To date, the scope of the issue has not been evaluated in Canada. In this study we developed a framework, in the form of a decision tree, to estimate the number of potentially PFAS impacted airport sites in Canada as a result of AFFF releases. The screening process was completed using publicly available resources including airport websites, the Canadian Owners and Pilots Association website, Sky Vector, Transport Safety Board of Canada aviation investigation reports, the Aviation Safety Network website, and Google maps. ...
A new method for the fast and simultaneous determination of Sb(III) and Sb(V) is presented involv... more A new method for the fast and simultaneous determination of Sb(III) and Sb(V) is presented involving the use of anion exchange high-performance liquid chromatography (HPLC), a complexing reagent in the mobile phase, and element specific detection with flame atomic absorption spectrometry (FAAS) or inductively coupled plasma mass spectrometry (ICP-MS). Chromatographic parameters such as nature and concentration of the complexing and eluting compounds and pH of the mobile phase were investigated in detail. Additionally, the separation of inorganic Sb(III) and Sb(V) from organically bounded antimony (as (CH 3) 3 SbCl 2 and (CH 3) 3 Sb(OH) 2) was investigated by using anion, and cation exchange, and reversed phase HPLC. Best separation was obtained with anion exchange HPLC under alkaline conditions. Cation exchange and reversed-phase HPLC were not useful for the separation of the above compounds. With FAAS concentrations in the upper mg L-1 range are detectable, which is not sensitive enough for the analyses of environmental samples. When the chromatographic system was coupled to ICP-MS, the detection limits are in the lower µg L-1 range. The method was applied to various environmental samples with anthropogenic and naturally elevated Sb concentrations.
Fruiting bodies from the Agaricus genus have been found to contain non-toxic arsenobetaine (AB) a... more Fruiting bodies from the Agaricus genus have been found to contain non-toxic arsenobetaine (AB) as a major compound. It is unknown whether AB is formed during the vegetative or reproductive life stages of the fungus, or by the surrounding microbial community, but AB's structural similarity to glycine betaine has led to the hypothesis that AB may be adventitiously accumulated as an osmolyte. To investigate the potential formation of AB during the reproductive life stage of Agaricus species, growth substrate and fungi were collected during the commercial growth of Agaricus bisporus and analyzed for arsenic speciation using HPLC-ICP-MS. AB was found to be the major arsenic compound in the fungus at the earliest growth stage of fruiting (the primordium). The growth substrate mainly contained arsenate (As(V)). The distribution of arsenic in an A. bisporus primordium grown on As(V) treated substrate, and in a mature Agaricus campestris fruiting body collected from arsenic contaminated...
We have used confocal methods to examine the distribution and speciation of arsenic within amphib... more We have used confocal methods to examine the distribution and speciation of arsenic within amphibian tissue (Bufo americanus) from a contaminated mine site. The use of new microchannel technology permits a confocal, and energy-independent, examination of a given voxel within the amphibian tissue without the need for sectioning. We observe differences in arsenic concentration and speciation depending on tissue type, with the Eberth- Katschenko layer in particular containing Mn, Fe, Cu and Zn in addition to Ca and pentavalent arsenic.
Arsenic compounds are widespread environmental contaminants and exposure elicits serious health i... more Arsenic compounds are widespread environmental contaminants and exposure elicits serious health issues, including early developmental anomalies. Depending on the oxidation state, the intermediates of arsenic metabolism interfere with a range of subcellular events, but the fundamental molecular events that lead to speciation-dependent arsenic toxicity are not fully elucidated. This study therefore assesses the impact of arsenic exposure on early development by measuring speciation and gene expression profiles in the developing Western clawed frog (Silurana tropicalis) larvae following the environmental relevant 0.5 and 1 ppm arsenate exposure. Using HPLC-ICP-MS, arsenate, dimethylarsenic acid, arsenobetaine, arsenocholine, and tetramethylarsonium ion were detected. Microarray and pathway analyses were utilized to characterize the comprehensive transcriptomic responses to arsenic exposure. Clustering analysis of expression data showed distinct gene expression patterns in arsenate treated groups when compared with the control. Pathway enrichment revealed common biological themes enriched in both treatments, including cell signal transduction, cell survival, and developmental pathways. Moreover, the 0.5 ppm exposure led to the enrichment of pathways and biological processes involved in arsenic intake or efflux, as well as histone remodeling. These compensatory responses are hypothesized to be responsible for maintaining an in-body arsenic level comparable to control animals. With no appreciable changes observed in malformation and mortality between control and exposed larvae, this is the first study to suggest that the underlying transcriptomic regulations related to signal transduction, cell survival, developmental pathways, and histone remodeling may contribute to maintaining ongoing development while coping with the potential arsenic toxicity in S. tropicalis during early development.
Life cycle exposure of the frog Silurana tropicalis to arsenate: Steroid-and thyroid hormone-rela... more Life cycle exposure of the frog Silurana tropicalis to arsenate: Steroid-and thyroid hormone-related genes are differently altered throughout development, General and Comparative Endocrinology (2015),
Organometallics in Environment and Toxicology, 2010
The widespread distribution of organoarsenic compounds has been reviewed in terms of the five kin... more The widespread distribution of organoarsenic compounds has been reviewed in terms of the five kingdoms of life. Over 50 organoarsenicals are described. Pathways for their formation are discussed and significant data gaps have been identified.
The invertebrate shredder Gammarus pulex L. is a key species for aquatic carbon turnover via litt... more The invertebrate shredder Gammarus pulex L. is a key species for aquatic carbon turnover via litter decomposition and can thrive in high-arsenic (As) environments. To understand their
Metallomics : integrated biometal science, Jan 12, 2015
Western clawed frog (Silurana tropicalis) embryos were exposed to control, low (nominally 0.5 mg ... more Western clawed frog (Silurana tropicalis) embryos were exposed to control, low (nominally 0.5 mg L(-1)) and high (nominally 1 mg L(-1)) arsenate (As(V)) culture water concentrations to investigate the effects of arsenic (As) on different life stages, namely tadpole (Nieuwkoop and Faber stage 56, NF56) and frog stages (NF66). The effects were assessed by measuring arsenic(+3) and DNA methyltransferases (AS3MT and DNMT1), as well as As speciation in the tissues. The As content in frog tissues increased with water As concentration. The As species observed by high performance liquid chromatography - inductively coupled plasma mass spectrometry (HPLC-ICPMS) were mostly inorganic, dimethylarsinic acid (DMA) and trimethylarsine oxide (TMAO). With solid state X-ray absorption near edge structure (XANES) analysis, arsenobetaine/tetramethylarsonium ion were also seen. AS3MT levels decreased upon low As exposure in NF56, rising again to control levels at the high As exposure. In NF66 tissues, ...
ABSTRACT In the process of performing risk assessments for humans or animals, it has been shown t... more ABSTRACT In the process of performing risk assessments for humans or animals, it has been shown that the assumption that all of a contaminant in an ingested matrix poses risk is not always accurate. Specifically, not all of the contaminant is bioavailable (absorbed by the body). Bioaccessibility, which is the fraction of a contaminant that dissolves in gastrointestinal conditions, is used to estimate bioavailability. This is because in vitro laboratory extractions can be used, since they have the potential to be cost effective, commercially viable, and comparable to bioavailability measurements. Bioaccessibility extractions were developed from the fields of pharmaceutical dissolution testing, nutrition, and safety, based on simulated gastric and intestinal fluids developed for those applications. In the development of a number of different methods, some groups have focused on simple methods with few chemicals that can be easily conducted in a laboratory, and others have targeted maximum physiological representativeness with its accompanying complexity (e.g., dynamic systems and incorporation of microorganisms). Bioaccessibility of inorganic contaminants is most susceptible to changes in pH, and organic contaminant bioaccessibility is most affected by organic content of the extraction fluid. Validation of several methods, accomplished by finding significant relationships between bioaccessibility and bioavailability results, has been demonstrated for arsenic, lead, and cadmium, and comparisons for organic contaminants indicate that several methods are promising. Regulatory agencies should be able to develop frameworks that allow bioaccessibility extractions to be relevant for use in risk assessment.
As mercury emissions continue and climate-mediated permafrost thaw increases the burden of this c... more As mercury emissions continue and climate-mediated permafrost thaw increases the burden of this contaminant in northern waters, Inuit from a Northwest passage community in the Canadian Arctic Archipelago pressed for an assessment of their subsistence catches. Sea-run salmonids (n = 537) comprising Arctic char (Salvelinus alpinus), lake trout (S. namaycush), lake whitefish (Coregonus clupeaformis), and cisco (C. autumnalis, C. sardinella) were analyzed for muscle mercury. Methylmercury is a neurotoxin and bioaccumulated with fish age, but other factors including selenium and other elements, diet and trophic level as assessed by stable isotopes of nitrogen (δ15N) and carbon (δ13C), as well as growth rate, condition, and geographic origin, also contributed depending on the species, even though all the fish shared a similar anadromous or sea-run life history. Although mean mercury concentrations for most of the species were ~0.09 µg·g−1 wet weight (ww), below the levels described in sev...
The identification of food fish bearing anthropogenic contaminants is one of many priorities for ... more The identification of food fish bearing anthropogenic contaminants is one of many priorities for Indigenous peoples living in the Arctic. Mercury (Hg), arsenic (As), and persistent organic pollutants including polychlorinated biphenyls (PCBs) are of concern, and these are reported, in some cases for the first time, for fish sampled in and around King William Island, located in Nunavut, Canada. More than 500 salmonids, comprising Arctic char, lake trout, lake whitefish, and ciscoes, were assayed for contaminants. The studied species are anadromous, migrating to the ocean to feed in the summers and returning to freshwater before sea ice formation in the autumn. Assessments of muscle Hg levels in salmonids from fishing sites on King William Island showed generally higher levels than from mainland sites, with mean concentrations generally below guidelines, except for lake trout. In contrast, mainland fish showed higher means for As, including non-toxic arsenobetaine, than island fish. L...
Versatile sample preparation platform for mixing, splitting and extraction on patterned surfaces ... more Versatile sample preparation platform for mixing, splitting and extraction on patterned surfaces and subsequent detection by a UV/vis smartphone spectrometer.
Assessing the extent to which emerging contaminants (ECs) such as perfluoroalkyl and polyfluoroal... more Assessing the extent to which emerging contaminants (ECs) such as perfluoroalkyl and polyfluoroalkyl substances (PFAS) have been released into the environment is one of the foundations for developing effective management and remediation strategies for impacted sites. PFAS are known to have caused the contamination of soil, groundwater, and surface water as a result of aqueous film forming foam (AFFF) being accidentally or intentionally released into the environment. To date, the scope of the issue has not been evaluated in Canada. In this study we developed a framework, in the form of a decision tree, to estimate the number of potentially PFAS impacted airport sites in Canada as a result of AFFF releases. The screening process was completed using publicly available resources including airport websites, the Canadian Owners and Pilots Association website, Sky Vector, Transport Safety Board of Canada aviation investigation reports, the Aviation Safety Network website, and Google maps. ...
A new method for the fast and simultaneous determination of Sb(III) and Sb(V) is presented involv... more A new method for the fast and simultaneous determination of Sb(III) and Sb(V) is presented involving the use of anion exchange high-performance liquid chromatography (HPLC), a complexing reagent in the mobile phase, and element specific detection with flame atomic absorption spectrometry (FAAS) or inductively coupled plasma mass spectrometry (ICP-MS). Chromatographic parameters such as nature and concentration of the complexing and eluting compounds and pH of the mobile phase were investigated in detail. Additionally, the separation of inorganic Sb(III) and Sb(V) from organically bounded antimony (as (CH 3) 3 SbCl 2 and (CH 3) 3 Sb(OH) 2) was investigated by using anion, and cation exchange, and reversed phase HPLC. Best separation was obtained with anion exchange HPLC under alkaline conditions. Cation exchange and reversed-phase HPLC were not useful for the separation of the above compounds. With FAAS concentrations in the upper mg L-1 range are detectable, which is not sensitive enough for the analyses of environmental samples. When the chromatographic system was coupled to ICP-MS, the detection limits are in the lower µg L-1 range. The method was applied to various environmental samples with anthropogenic and naturally elevated Sb concentrations.
Fruiting bodies from the Agaricus genus have been found to contain non-toxic arsenobetaine (AB) a... more Fruiting bodies from the Agaricus genus have been found to contain non-toxic arsenobetaine (AB) as a major compound. It is unknown whether AB is formed during the vegetative or reproductive life stages of the fungus, or by the surrounding microbial community, but AB's structural similarity to glycine betaine has led to the hypothesis that AB may be adventitiously accumulated as an osmolyte. To investigate the potential formation of AB during the reproductive life stage of Agaricus species, growth substrate and fungi were collected during the commercial growth of Agaricus bisporus and analyzed for arsenic speciation using HPLC-ICP-MS. AB was found to be the major arsenic compound in the fungus at the earliest growth stage of fruiting (the primordium). The growth substrate mainly contained arsenate (As(V)). The distribution of arsenic in an A. bisporus primordium grown on As(V) treated substrate, and in a mature Agaricus campestris fruiting body collected from arsenic contaminated...
We have used confocal methods to examine the distribution and speciation of arsenic within amphib... more We have used confocal methods to examine the distribution and speciation of arsenic within amphibian tissue (Bufo americanus) from a contaminated mine site. The use of new microchannel technology permits a confocal, and energy-independent, examination of a given voxel within the amphibian tissue without the need for sectioning. We observe differences in arsenic concentration and speciation depending on tissue type, with the Eberth- Katschenko layer in particular containing Mn, Fe, Cu and Zn in addition to Ca and pentavalent arsenic.
Arsenic compounds are widespread environmental contaminants and exposure elicits serious health i... more Arsenic compounds are widespread environmental contaminants and exposure elicits serious health issues, including early developmental anomalies. Depending on the oxidation state, the intermediates of arsenic metabolism interfere with a range of subcellular events, but the fundamental molecular events that lead to speciation-dependent arsenic toxicity are not fully elucidated. This study therefore assesses the impact of arsenic exposure on early development by measuring speciation and gene expression profiles in the developing Western clawed frog (Silurana tropicalis) larvae following the environmental relevant 0.5 and 1 ppm arsenate exposure. Using HPLC-ICP-MS, arsenate, dimethylarsenic acid, arsenobetaine, arsenocholine, and tetramethylarsonium ion were detected. Microarray and pathway analyses were utilized to characterize the comprehensive transcriptomic responses to arsenic exposure. Clustering analysis of expression data showed distinct gene expression patterns in arsenate treated groups when compared with the control. Pathway enrichment revealed common biological themes enriched in both treatments, including cell signal transduction, cell survival, and developmental pathways. Moreover, the 0.5 ppm exposure led to the enrichment of pathways and biological processes involved in arsenic intake or efflux, as well as histone remodeling. These compensatory responses are hypothesized to be responsible for maintaining an in-body arsenic level comparable to control animals. With no appreciable changes observed in malformation and mortality between control and exposed larvae, this is the first study to suggest that the underlying transcriptomic regulations related to signal transduction, cell survival, developmental pathways, and histone remodeling may contribute to maintaining ongoing development while coping with the potential arsenic toxicity in S. tropicalis during early development.
Life cycle exposure of the frog Silurana tropicalis to arsenate: Steroid-and thyroid hormone-rela... more Life cycle exposure of the frog Silurana tropicalis to arsenate: Steroid-and thyroid hormone-related genes are differently altered throughout development, General and Comparative Endocrinology (2015),
Organometallics in Environment and Toxicology, 2010
The widespread distribution of organoarsenic compounds has been reviewed in terms of the five kin... more The widespread distribution of organoarsenic compounds has been reviewed in terms of the five kingdoms of life. Over 50 organoarsenicals are described. Pathways for their formation are discussed and significant data gaps have been identified.
The invertebrate shredder Gammarus pulex L. is a key species for aquatic carbon turnover via litt... more The invertebrate shredder Gammarus pulex L. is a key species for aquatic carbon turnover via litter decomposition and can thrive in high-arsenic (As) environments. To understand their
Metallomics : integrated biometal science, Jan 12, 2015
Western clawed frog (Silurana tropicalis) embryos were exposed to control, low (nominally 0.5 mg ... more Western clawed frog (Silurana tropicalis) embryos were exposed to control, low (nominally 0.5 mg L(-1)) and high (nominally 1 mg L(-1)) arsenate (As(V)) culture water concentrations to investigate the effects of arsenic (As) on different life stages, namely tadpole (Nieuwkoop and Faber stage 56, NF56) and frog stages (NF66). The effects were assessed by measuring arsenic(+3) and DNA methyltransferases (AS3MT and DNMT1), as well as As speciation in the tissues. The As content in frog tissues increased with water As concentration. The As species observed by high performance liquid chromatography - inductively coupled plasma mass spectrometry (HPLC-ICPMS) were mostly inorganic, dimethylarsinic acid (DMA) and trimethylarsine oxide (TMAO). With solid state X-ray absorption near edge structure (XANES) analysis, arsenobetaine/tetramethylarsonium ion were also seen. AS3MT levels decreased upon low As exposure in NF56, rising again to control levels at the high As exposure. In NF66 tissues, ...
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