Human biomonitoring of dioxins, furans, and non-ortho dioxin-like polychlorinated biphenyls (PCBs) in blood plasma from Old Crow, Yukon, Canada (2019)

Dioxins, furans, and dioxin-like polychlorinated biphenyls (PCBs) are a group of persistent and toxic chemicals that are known to have human health effects at low levels. These chemicals have been produced for commercial use (PCBs) or unintentionally as by-products of industry or natural processes (PCBs, dioxins, and furans). Additionally, dioxin-like PCBs were formerly used in electrical applications before being banned internationally (2004). These chemicals are widely dispersed in the environment as they can contaminate air and travel hundreds to thousands of kilometers before depositing on land or water, thereafter, potentially entering food chains. Community concerns surrounding the safety of traditional foods prompted a human biomonitoring project in Old Crow, Yukon Territory (YT), Canada (2019). Through collaborative community engagement, dioxins and like compounds were identified as a priority for exposure assessment from biobanked samples. In 2022, biobanked plasma samples (n = 54) collected in Old Crow were used to measure exposures to seven dioxins, ten furans, and four dioxin-like PCBs. 1,2,3,6,7,8-HxCDD, 1,2,3,7,8,9-HxCDD, 1,2,3,4,6,7,8-HpCDD, OCDD, 2,3,4,7,8-PeCDF, 1,2,3,6,7,8-HxCDF, PCB 126, and PCB 169 were detected in at least 50 % of samples. Among these analytes, the only congener at elevated levels was PCB 169, which was approximately ∼2-fold higher than the general population of Canada. No significant sex-based or body mass index (BMI) differences in biomarker concentrations were observed. Generally, the concentrations of the detected congeners increased with age, except for 1,2,3,4,6,7,8-HpCDD. For the first time, this research measures dioxin and like-compound exposures in Old Crow, advancing the information available on chemical exposures in the Arctic. Further research could be directed towards the investigation of PCB 169 exposure sources and temporal monitoring of exposures and determinants.

Hexachlorobenzene and omega-3 fatty acid intake from traditional foods in the northern Yukon: A risk and benefit analysis

A human biomonitoring study was conducted in the community of Old Crow, Yukon, in 2019, finding that levels of hexachlorobenzene (HCB) in plasma were elevated in the community relative to the general Canadian population. The aim of this study was to estimate dietary intake of both hexachlorobenzene, and the nutrient omega-3 fatty acids from locally harvested traditional foods in Old Crow, with the aim of identifying possible regional sources of exposure. A stochastic model was constructed to estimate intake of both hexachlorobenzene and the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Average predicted hexachlorobenzene exposure levels from traditional food consumption in Old Crow were below the tolerable daily intake of 1600-1700 ng/kg body weight/day in both average (18 ng/kg body weight/day) and short-term maximum (27 ng/kg body weight/day) exposure models. The primary contributors to average hexachlorobenzene intake were caribou fat, bone marrow, ribs, and kidneys, and Chinook salmon muscle. Average estimated dietary EPA + DHA intake levels from traditional foods were below the recommendation of 2.1 to 3.2 g of EPA + DHA per week in the average (1.6 g/week) exposure model, but above this recommendation in the short-term maximum model (3.3 g/week). The primary contributors to average EPA + DHA intake were the meat of Chinook, coho, and, chum salmon muscle, and whitefish muscle and eggs. The results of this study support the message that traditional foods continue to be an important source of nutrients and other health benefits and that the health benefits of traditional foods generally outweigh contaminant risks.

Prenatal and concurrent blood mercury concentrations and associations with IQ in canadian preschool children

BACKGROUND

Prenatal and childhood mercury (Hg) exposures have been associated with negative impacts on child neurodevelopment. It is unclear if associations persist at the low Hg exposures typical in Western countries.

OBJECTIVE

To examine associations between prenatal/childhood blood Hg concentrations and child IQ in Canadian male and female children while considering the potential modifying role of prenatal fish consumption.

METHODS

We analyzed data from the Maternal-Infant Research on Environmental Chemicals study. Hg was measured in first trimester (n = 527), cord (n = 430), and child (at 3-4 years of age, n = 355) blood and examined sex-stratified associations between blood Hg and children's Full Scale IQ (FSIQ), Verbal IQ (VIQ), Performance IQ (PIQ), and General Language Composite (GLC) scores (assessed with WPPSI-III). Prenatal Hg analyses were further stratified by prenatal fish consumption (low: 0-2, moderate: 3-7, or high: ≥8 times/month).

RESULTS

Higher cord blood Hg concentrations were associated with lower PIQ (ß = -3.27; 95%CI: 6.44, -0.09) in male children with the lowest prenatal fish consumption. Progressively stronger positive associations were observed with PIQ in male children for moderate (ß = 1.08; 95%CI: 0.10, 2.26) and high (ß = 3.07; 95%CI: 1.95, 4.19) prenatal fish consumption. Cord blood Hg concentrations were positively associated with female children's FSIQ (ß = 1.29; 95% CI: 0.77, 1.81) and PIQ (ß = 2.01; 95% CI: 1.19, 2.83); however, when stratified only in the highest fish consumption subgroup. Among female children, higher child blood Hg concentrations were associated with an approximately 1-point increase in FSIQ, VIQ, and GLC.

CONCLUSIONS

Prenatal exposure to low levels of Hg was associated with lower PIQ scores in male children with low prenatal fish intake. Positive associations between cord and child blood Hg concentrations and IQ were primarily observed in female children and may be due to beneficial effects of prenatal fish intake.

Estimates, spatial variability, and environmental drivers of mercury biomagnification rates through lake food webs in the Canadian subarctic

Biomagnification of mercury (Hg) through lake food webs is understudied in rapidly changing northern regions, where wild-caught subsistence fish are critical to food security. We investigated estimates and among-lake variability of Hg biomagnification rates (BMR), relationships between Hg BMR and Hg levels in subsistence fish, and environmental drivers of Hg BMR in ten remote subarctic lakes in Northwest Territories, Canada. Lake-specific linear regressions between Hg concentrations (total Hg ([THg]) in fish and methyl Hg ([MeHg]) in primary consumers) and baseline-adjusted δ¹⁵N ratios were significant (p < 0.001, r² = 0.58-0.88), indicating biomagnification of Hg through food webs of all studied lakes. Quantified using the slope of Hg-δ¹⁵N regressions, Hg BMR ranged from 0.16 to 0.25, with mean ± standard deviation of 0.20 ± 0.03). Using fish [MeHg] rather than [THg] lowered estimates of Hg BMR by ∼10%, suggesting that the use of [THg] as a proxy for [MeHg] in fish can influence estimates of Hg BMR. Among-lake variability of size-standardized [THg] in resident fish species from different trophic guilds, namely Lake Whitefish (Coregonus clupeaformis) and Northern Pike (Esox lucius), was not significantly explained by among-lake variability in Hg BMR. Stepwise multiple regressions indicated that among-lake variability of Hg BMR was best explained by a positive relationship with catchment forest cover (p = 0.009, r² = 0.59), likely reflecting effects of forest cover on water chemistry of downstream lakes and ultimately, concentrations of biomagnifying MeHg (and percent MeHg of total Hg) in resident biota. These findings improve our understanding of Hg biomagnification in remote subarctic lakes.

Understanding among-lake variability of mercury concentrations in Northern Pike (Esox lucius): A whole-ecosystem study in subarctic lakes

Mercury concentrations ([Hg]) in fish reflect complex biogeochemical and ecological interactions that occur at a range of spatial and biological scales. Elucidating these interactions is crucial to understanding and predicting fish [Hg], particularly at northern latitudes, where environmental perturbations are having profound effects on land-water-animal interactions, and where fish are a critical subsistence food source. Using data from eleven subarctic lakes that span an area of ~60,000 km² in the Dehcho Region of Northwest Territories (Canada), we investigated how trophic ecology and growth rates of fish, lake water chemistry, and catchment characteristics interact to affect [Hg] in Northern Pike (Esox lucius), a predatory fish of widespread subsistence and commercial importance. Results from linear regression and piecewise structural equation models showed that 83% of among-lake variability in Northern Pike [Hg] was explained by fish growth rates (negative) and concentrations of methyl Hg ([MeHg]) in benthic invertebrates (positive). These variables were in turn influenced by concentrations of dissolved organic carbon, MeHg (water), and total Hg (sediment) in lakes, which were ultimately driven by catchment characteristics. Lakes in relatively larger catchments and with more temperate/subpolar needleleaf and mixed forests had higher [Hg] in Northern Pike. Our results provide a plausible mechanistic understanding of how interacting processes at scales ranging from whole catchments to individual organisms influence fish [Hg], and give insight into factors that could be considered for prioritizing lakes for monitoring in subarctic regions.

Human biomonitoring results of contaminant and nutrient biomarkers in Old Crow, Yukon, Canada

Several large-scale human biomonitoring projects have been conducted in Canada, including the Canadian Health Measures Survey (CHMS) and the First Nations Biomonitoring Initiative (FNBI). However, neither of these studies included participants living in the Yukon. To address this data gap, a human biomonitoring project was implemented in Old Crow, a fly-in Gwich'in community in the northern Yukon. The results of this project provide baseline levels of contaminant and nutrient biomarkers from Old Crow in 2019. Samples of hair, blood, and/or urine were collected from approximately 44% of community residents (77 of 175 adults). These samples were analyzed for contaminants (including heavy metals and persistent organic pollutants (POPs)), and nutrients (including trace elements and omega-3 fatty acids). Levels of these analytes were compared to health-based guidance values, when available, and results from other human biomonitoring projects in Canada. Levels of lead (GM 0.64 μg/g creatinine in urine/24 μg/L blood), cadmium (GM 0.32 μg/g creatinine in urine/0.85 μg/L blood), and mercury (GM < LOD in urine/0.76 μg/L blood/0.31 μg/g hair) were below select health-based guidance values for more than 95% of participants. However, compared to the general Canadian population, elevated levels of some contaminants, including lead (approximately 2× higher), cobalt (approximately 1.5× higher), manganese (approximately 1.3× higher), and hexachlorobenzene (approximately 1.5× higher) were observed. In contrast, levels of other POPs, including insecticides such as dichlorodiphenyltrichloroethane (DDT), its metabolite, dichlorodiphenyldichloroethylene (DDE), and polychlorinated biphenyls (PCBs) were similar to, or lower than, those reported in the general Canadian population. This study can be used along with future biomonitoring programs to evaluate the effectiveness of international initiatives designed to reduce the contaminant burden in the Arctic, including the Stockholm Convention and the Minamata Convention. Regionally, this project complements environmental monitoring being conducted in the region, informing local and regional traditional food consumption advisories.

Effects of chemical speciation on the bioaccessibility of zinc in spiked and smelter-affected soils

Previous studies have suggested that understanding soil metal speciation, rather than relying solely on total metal content, can improve the accuracy and utility of contaminated site risk assessments. Because soil properties and reaction time can alter metal speciation, speciation should influence metal bioaccessibility. For example, under gastrointestinal conditions, it is expected that metal species will differ in bioaccessibility depending on their stability in acidic pH environments. We studied the links between metal speciation and bioaccessibility. A combination of synchrotron-based X-ray diffraction and X-ray absorption near edge structure (XANES) was used to identify the zinc (Zn) speciation in spiked and smelter-affected soils. After conducting in vitro digestion tests on the soil samples, XANES and linear combination fitting were carried out on the residual pellets to identify the species of Zn that remained after digesting the soils in the simulated gastric and duodenal fluids. The metal species that were not present in the residual pellets were inferred to have been dissolved and, thus, more bioaccessible. Sphalerite (ZnS), ZnO, and outer-sphere Zn contributed more to Zn bioaccessibility than franklinite (ZnFe₂ O₄ ) and Zn incorporated into a hydroxy interlayer mineral (Zn-HIM). The bioaccessibility of Zn-aluminum layered double hydroxides (Zn-Al-LDH) was found to be inversely proportional to its residence time in soil. It was also observed that the relatively high pH of the duodenum favors metal reprecipitation and readsorption, leading to a reduction in bioaccessible metal concentration. These results imply that metal speciation mainly controls metal bioaccessibility. Environ Toxicol Chem 2019;38:448-459. © 2018 SETAC.

Implementation of human biomonitoring in the Dehcho region of the Northwest Territories, Canada (2016-2017)

Background

Human biomonitoring represents an important tool for health risk assessment, supporting the characterization of contaminant exposure and nutrient status. In communities where country foods (locally harvested foods: land animals, fish, birds, plants) are integrated in the daily diet, as is the case in remote northern regions where food security is a challenge, such foods can potentially be a significant route of contaminant exposure. To assess this issue, a biomonitoring project was implemented among Dene/Métis communities of the Dehcho region of the Northwest Territories, Canada.

Methods

Participants completed dietary surveys (i.e., a food frequency questionnaire and 24-h recall) to estimate food consumption patterns as well as a Health Messages Survey to evaluate the awareness and perception of contaminants and consumption notices. Biological sampling of hair, urine and blood was conducted. Toxic metals (e.g., mercury, lead, cadmium), essential metals (e.g., copper, nickel, zinc), fatty acids, and persistent organic pollutants (POPs) were measured in samples.

Results

The levels of contaminants in blood, hair and urine for the majority of participants were below the available guidance values for mercury, cadmium, lead and uranium. However, from the 279 participants, approximately 2% were invited to provide follow up samples, mainly for elevated mercury level. Also, at the population level, blood lead (GM: 11 μg/L) and blood cadmium (GM: 0.53 μg/L) were slightly above the Canadian Health Measures Survey data. Therefore, although country foods occasionally contain elevated levels of particular contaminants, human exposures to these metals remained similar to those seen in the Canadian general population. In addition, dietary data showed the importance and diversity of country foods across participating communities, with the consumption of an average of 5.1% of total calories from wild-harvested country foods.

Conclusion

This project completed in the Mackenzie Valley of the Northwest Territories fills a data gap across other biomonitoring studies in Canada as it integrates community results, will support stakeholders in the development of public health strategies, and will inform environmental health issue prioritization.

Electronic supplementary material

The online version of this article (10.1186/s13690-018-0318-9) contains supplementary material, which is available to authorized users.

Cadmium exposure in First Nations communities of the Northwest Territories, Canada: smoking is a greater contributor than consumption of cadmium-accumulating organ meats

Traditional food consumption among northern populations is associated with improved nutrition but occasionally can also increase contaminant exposure. High levels of cadmium in the organs of moose from certain regions of the Northwest Territories, Canada, led to the release of consumption notices. These notices recommended that individuals limit their consumption of kidney and liver from moose harvested from the Southern Mackenzie Mountain. A human biomonitoring project was designed to better characterize exposure and risks from contaminants, including cadmium, among Dene/Métis communities of the Northwest Territories Mackenzie Valley, Canada. The project included a dietary assessment (food frequency questionnaire) to estimate moose and caribou organ (kidney and liver) consumption, as well as urine and blood sampling for the measurement of cadmium concentration using mass spectrometry. For a subset of the samples, urine cotinine was also quantified. The results from this biomonitoring research show that cadmium levels in urine (GM = 0.32 μg L-1) and blood (GM = 0.58 μg L-1) are similar to those observed in other populations in Canada. For the 38% of participants reporting eating game organs, current traditional food consumption patterns were not associated with cadmium biomarker levels. Instead, smoking appeared to be the main determinant of cadmium exposure. These results are supporting ongoing efforts at the community and territorial level to identify health priorities and design follow up plans in response to environmental monitoring data.

Mercury and omega-3 fatty acid profiles in freshwater fish of the Dehcho Region, Northwest Territories: Informing risk benefit assessments

Traditional foods have significant nutritional, sociocultural and economic value in subarctic First Nations communities of the Northwest Territories, and play a crucial role in promoting cultural continuity and sovereignty. Omega-3 polyunsaturated fatty acids (N-3 PUFAs), including eicosapentaenoic (EPA) and docosahexaenoic acid (DHA), carry significant benefits for neurocognitive development and cardiovascular health. However, the health risks posed by methylmercury may serve to undermine the benefits of fish consumption in Northern Indigenous communities. The objective of this study was to characterize profiles for mercury (Hg) and fatty acids in fish species harvested across lakes of the Dehcho Region, in the Mackenzie Valley of the Northwest Territories, to better understand the risks and benefits associated with traditional foods. Hg levels increased with trophic position, with the highest levels found in Burbot, Lake Trout, Walleye, and Northern Pike. Lake Trout, along with planktivorous species including Lake Whitefish, Cisco, and Sucker, demonstrated higher N-3 PUFAs than other species. Negative associations were observed between Hg and N-3 PUFAs in Lake Trout, Northern Pike, Walleye and Burbot. Further stratifying these relationships revealed significant interactions by lake. Significant differences observed in fatty acid and Hg profiles across lakes underscore the importance of considering both species- and lake-specific findings. This growing dataset of freshwater fish of the Dehcho will inform future efforts to characterize human Hg exposure profiles using probabilistic dose reconstruction models.

Mercury diminishes the cardiovascular protective effect of omega-3 polyunsaturated fatty acids in the modern diet of Inuit in Canada

BACKGROUND

Inuit in Canada have low reported incidence of myocardial infarction (MI) because of their traditional rich n-3 fatty acids marine diet. They are experiencing rapid nutrition transition and ischemic heart disease is now becoming a health concern.

OBJECTIVES

Our goal was to describe the modern Inuit diet, the eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and methyl mercury (MeHg) intake and estimate their contributions to the risk of MI. We also estimated the effect of promoting the consumption of more traditional food on Inuit's MI risk.

METHODS

We estimated the effect of Inuit diet on MI risk with modelling. Model formulas and assumptions were extracted from various epidemiology studies and literatures. International Polar Year Inuit Health Survey (IHS) was a comprehensive health and nutrition survey conducted in 2007-8 with 2072 participants (aged 18-79) in Canada. Traditional food intake, blood biomarkers values from the IHS served as the baseline parameters of model input.

RESULTS

Inuit traditional diet contained both high level of EPA, DHA and MeHg and their combined net effect was estimated to reduce the relative risk of MI by 1% for men and 2% for women. Arctic char meat provided the largest amount of EPA and DHA. Ringed seal liver was the main source for MeHg. Increase intake of selected fish, like salmon, herring and Arctic char by 75g per day can reduce the relative risk of MI (RR 0.70, 0.78 and 0.90 respectively).

CONCLUSIONS

In the Inuit diet, the beneficial effect on MI of EPA and DHA is diminished by the adverse effect of MeHg. Promoting the increase consumption of fish species with high EPA+DHA and low MeHg may help to prevent MI among Inuit.

Associations between omega-3 fatty acids, selenium content, and mercury levels in wild-harvested fish from the Dehcho Region, Northwest Territories, Canada

To better understand the risks and benefits of eating wild-harvested fish from the Northwest Territories, Canada, levels of total mercury (HgT) and selenium (Se) and composition of omega-3 fatty acid (n-3 FA) were measured in muscle tissue of fish harvested from lakes in the Dehcho Region, Northwest Territories, Canada. Average HgT levels ranged from 0.057 mg/kg (cisco) to 0.551 mg/kg (northern pike), while average n-3 FA concentrations ranged from 101 mg/100 g (burbot) to 1,689 mg/100 g (lake trout). In contrast to HgT and n-3 FA, mean Se concentrations were relatively similar among species. Consequently, species such as lake whitefish, cisco, and longnose sucker displayed the highest nutrient levels relative to HgT content. Levels of HgT tended to increase with fish size, while Se and n-3 FA levels were typically not associated with fork length or fish weight. Interestingly, HgT concentration was occasionally inversely related to tissue nutrient content. Significant negative correlations were observed between Hg and n-3 FA for lake trout, northern pike, and walleye. There were also significant negative correlations between Hg and Se noted for lake whitefish, cisco, and northern pike. Samples with the highest nutritional content displayed, on occasion, lower levels of HgT. This study provides valuable information for the design of probabilistic models capable of refining public health messaging related to minimizing Hg risks and maximizing nutrient levels in wild-harvested fish in the Canadian subarctic.

Solid-liquid separation method governs the in vitro bioaccessibility of metals in contaminated soil-like test materials

An in vitro gastrointestinal model was used to explore the role of solid-liquid separation method on the bioaccessibility of trace elements in a smelter-impacted soil (NIST-2711) from Helena, MT and a mine overburden from an open-pit gold and silver mine in Mount Nansen, YK (YK-OVB). Separation methods studied included centrifugation (5,000 g, 12,000 g), syringe microfiltration (0.45 μm), and ultrafiltration (1,000 kDa, 50 kDa, 30 kDa, 10 kDa, 3 kDa). Results indicated that the use of syringe microfiltration generally yields the same bioaccessibility as the use of centrifugation and that the speed of centrifugation does not typically affect metal bioaccessibility. However, ultrafiltration consistently yields a significantly lower bioaccessibility than the use of centrifugation and syringe microfiltration. There are rarely any differences between bioaccessibility estimates generated using a low-resistance (1,000 kDa) and a high-resistance (3 kDa) ultrafiltration membrane; therefore, under the in vitro gastrointestinal conditions modeled herein, negligible quantities of trace elements are complexed to small molecules between 3 and 1,000 kDa. The primary exceptions to these trends were observed for Pb in NIST-2711 (5,000 g>12,000 g>0.45 μm>ultrafiltration) and for Tl in NIST-2711 and YK-OVB (5000 g∼12,000 g>0.45 μm>ultrafiltration). These results provide valuable information to researchers attempting to expand the use of in vitro bioaccessibility beyond soil Pb and As.

Relationship between the esterase paraoxonase-1 (PON1) and metal concentrations in the whole blood of Inuit in Canada

The esterase paraoxonase (PON1), a major component of high-density lipoprotein (HDL), protects against the development of atherosclerosis in humans. Although variation in PON1 activity is primarily governed by PON1 genotype, there is growing evidence that environmental chemicals may also modulate its activity. This cross-sectional study aimed to determine whether environmental exposure to various metals is associated with PON1 activity in Inuit people routinely exposed to mercury (Hg), cadmium (Cd), lead (Pb), and (Se) selenium. PON1 activity and metal concentrations were measured in blood collected from 2172 healthy participants. Sociodemographic, anthropometric and lifestyle variables were also assessed. The associations between PON1 activity and blood metal concentrations, HDL, omega-3 fatty acid blood levels, age, sex, body mass index (BMI), and lifestyle habits (e.g. smoking and alcohol consumption) were explored via multiple linear regression. PON1 activity was positively associated with Se blood concentration (β=0.056, P=0.001) but was negatively associated with Cd blood concentration (β=-0.025, P<0.001). No association was observed between PON1 activity and Hg or Pb blood concentrations. Our results suggest that: PON1 activity is modulated by metal exposure, and Inuit traditional foods may confer health benefit by increasing PON1 activity via higher Se intakes. These findings underline that current environmental metal exposures among Inuit living in the Canadian Arctic are associated with paraoxonase activity, a toxicologically-relevant biochemical parameter.

Body burden of metals and persistent organic pollutants among Inuit in the Canadian Arctic

Inuit living in the Arctic are exposed to elevated levels of environmental contaminants primarily due to long-range atmospheric transport. Blood sampling and contaminant biomonitoring was conducted as part of the International Polar Year Inuit Health Survey in 2007-2008. The body burden of metals (e.g. Cd, Pb) and persistent organic pollutants (e.g. PCBs, DDT & DDE, toxaphene, chlordane, PBDEs) were measured for Inuit participants (n=2172) from 36 communities in Nunavut, Nunatsiavut, and the Inuvialuit Settlement Region, in Canada. The geometric mean of blood concentrations for Cd, Pb, PCBs, DDE & DDT, toxaphene, and chlordane were higher than those in the Canadian general population. A total of 9% of study participants exceeded the intervention guideline of 100μgL(-1) for Pb, 11% of participants exceeded the trigger guideline of 5μgL(-1) for Cd, and 1% exceeded the intervention guideline of 100μgL(-1) for PCBs. Also, 3% of women of child-bearing age exceeded blood Pb of 100μgL(-1) while 28% of women of child-bearing age exceeded 5μgL(-1) of PCBs. This work showed that most Inuit Health Survey participants were below blood contaminant guidelines set by Health Canada but that metal and POP body burdens commonly exceed exposures observed in the general population of Canada.

Dietary advice on Inuit traditional food use needs to balance benefits and risks of mercury, selenium, and n3 fatty acids

Elevated concentrations of mercury (Hg) are commonly found in the traditional foods, including fish and marine mammals, of Inuit living in Canada's Arctic. As a result, Inuit often have higher dietary Hg intake and elevated Hg blood concentrations. However, these same traditional foods are excellent sources of essential nutrients. The goals of this study were 1) to identify the traditional food sources of Hg exposure for Inuit, 2) to estimate the percentage of Inuit who meet specific nutrient Dietary Reference Intakes and/or exceed the Toxicological Reference Values (TRVs), and 3) to evaluate options that maximize nutrient intake while minimizing contaminant exposure. A participatory cross-sectional survey was designed in consultation with Inuit in 3 Canadian Arctic jurisdictions (Nunatsiavut, Nunavut, and the Inuvialuit Settlement Region). Estimated intakes for EPA (20:5n3) and DHA (22:6n3) met suggested dietary targets, and estimated selenium (Se) intake fell within the Acceptable Range of Oral Intake. Estimated intakes of Hg (rs = 0.41, P < 0.001), Se (rs = 0.44, P < 0.001), EPA (rs = 0.32, P < 0.001), and DHA (rs = 0.28, P < 0.001) were correlated with their respective blood concentrations. Mean estimated Hg intake (7.9 μg · kg(-1) · wk(-1)) exceeded the TRV of 5.0 μg · kg(-1) · wk(-1), with 35% of the population above this guideline. Because the estimated intakes of each of the nutrients were strongly correlated (Se: rs = 0.92, P < 0.001; EPA: rs = 0.82, P < 0.001; DHA: rs = 0.81, P < 0.001) with estimated Hg intake, efforts to decrease Hg exposure must emphasize the overall healthfulness of traditional foods and be designed to prevent concomitant harm to the nutrient intakes of Inuit.

Dietary advice on Inuit traditional food use needs to balance benefits and risks of mercury, selenium, and n3 fatty acids

Elevated concentrations of mercury (Hg) are commonly found in the traditional foods, including fish and marine mammals, of Inuit living in Canada's Arctic. As a result, Inuit often have higher dietary Hg intake and elevated Hg blood concentrations. However, these same traditional foods are excellent sources of essential nutrients. The goals of this study were 1) to identify the traditional food sources of Hg exposure for Inuit, 2) to estimate the percentage of Inuit who meet specific nutrient Dietary Reference Intakes and/or exceed the Toxicological Reference Values (TRVs), and 3) to evaluate options that maximize nutrient intake while minimizing contaminant exposure. A participatory cross-sectional survey was designed in consultation with Inuit in 3 Canadian Arctic jurisdictions (Nunatsiavut, Nunavut, and the Inuvialuit Settlement Region). Estimated intakes for EPA (20:5n3) and DHA (22:6n3) met suggested dietary targets, and estimated selenium (Se) intake fell within the Acceptable Range of Oral Intake. Estimated intakes of Hg (rs = 0.41, P < 0.001), Se (rs = 0.44, P < 0.001), EPA (rs = 0.32, P < 0.001), and DHA (rs = 0.28, P < 0.001) were correlated with their respective blood concentrations. Mean estimated Hg intake (7.9 μg · kg(-1) · wk(-1)) exceeded the TRV of 5.0 μg · kg(-1) · wk(-1), with 35% of the population above this guideline. Because the estimated intakes of each of the nutrients were strongly correlated (Se: rs = 0.92, P < 0.001; EPA: rs = 0.82, P < 0.001; DHA: rs = 0.81, P < 0.001) with estimated Hg intake, efforts to decrease Hg exposure must emphasize the overall healthfulness of traditional foods and be designed to prevent concomitant harm to the nutrient intakes of Inuit.

Bioaccessibility of metals in fish, shellfish, wild game, and seaweed harvested in British Columbia, Canada

Fish, shellfish, wild game, and seaweed are important traditional foods that are essential to the physical and cultural well-being of Indigenous peoples in Canada. The goal of this study was to measure the concentration and bioaccessibility of As, Cd, Hg, Se, Cu and Mn in 45 commonly consumed traditional foods collected by harvested by the First Nations Food, Nutrition, and Environment Study (FNFNES) from 21 First Nations communities in British Columbia, Canada, in 2008-2009. A significant and negative correlation was observed between Hg concentration and Hg bioaccessibility. Metal bioaccessibility tended to be high; median values ranging between 52% (Mn) and 83% (Cu). The notable exceptions were observed for As in wild game organs (7-19%) and rabbit meat (4%) as well as Hg in salmon eggs (10%). Results of Principal Components Analysis confirmed the unique pattern of bioaccessibility of As and Hg in traditional foods, suggesting that, unlike other metals, As and Hg bioaccessibility are not simply controlled by food digestibility under the operating conditions of the in vitro model. These data provide useful information for dietary contaminant risk assessment and intake assessments of essential trace elements.

An investigation of the effect of gastrointestinal microbial activity on oral arsenic bioavailability

In vitro gastrointestinal (GI) microbial activity in the colon compartment facilitates the arsenic release from soils into simulated GI fluids. Consequentially, it is possible that in vitro models that neglect to include microbial activity underestimate arsenic bioaccessibility when calculating oral exposure. However, the toxicological relevance of increased arsenic release due to microbial activity is contingent upon the subsequent absorption of arsenic solubilized in the GI lumen. The objectives of this research are to: (1) assess whether microbes in the in vitro small intestine affect arsenic solubilization from soils, (2) determine whether differences in the GI microbial community result in differences in the oral bioavailability of soil-borne arsenic. In vitro GI microbial activity in the distal small intestine increased arsenic release from soils; however, these effects were unlikely to be relevant since they were transient and demonstrated small effect sizes. In vivo arsenic absorption for juvenile swine was unaffected by antibiotic treatment. Therefore, it appears that microbial effects on arsenic release do not result in increased arsenic bioavailability. However, it remains to be seen whether the results for the limited set of soils described herein can be extrapolated to arsenic contaminated sites in general.

Human exposure assessment: a case study of 8 PAH contaminated soils using in vitro digestors and the juvenile swine model

In vitro digestors can be used to provide bioaccessibility values to help assess the risk from incidental human ingestion of contaminated soils. It has been suggested that these digestors may need to include a lipid sink to mimic human uptake processes. We compare the correspondence between in vivo polycyclic aromatic hydrocarbon (PAH) uptake for eight different PAH contaminated soils with PAH release in in vitro digestors in the presence and absence of a lipid sink. Lipid sinks were essential to the success of the in vitro digestors in predicting juvenile swine PAH uptake. In the presence of the lipid sink, results of the In Vitro Digestion model (IVD) closely corresponded with a slope of 0.85 (r(2) = 0.45, P < 0.07) to the in vivo results. The Relative Bioaccessibility Leaching Procedure (RBALP) results did not correspond to the in vivo study but did tightly reflect total soil PAH concentration. We conclude that the basis of this difference between digestors is that the RBALP used an aggressive extraction technique that maximized PAH release from soil. Systemic uptake in juvenile swine was not linked to soil PAH concentration but rather to the thermodynamic properties of the soil.

Bioaccessibility of metal cations in soil is linearly related to its water exchange rate constant

Site-specific risk assessments often incorporate the concepts of bioaccessibility (i.e., contaminant fraction released into gastrointestinal fluids) or bioavailability (i.e., contaminant fraction absorbed into systemic circulation) into the calculation of ingestion exposure. We evaluated total and bioaccessible metal concentrations for 19 soil samples under simulated stomach and duodenal conditions using an in vitro gastrointestinal model. We demonstrated that the median bioaccessibility of 23 metals ranged between <1 and 41% under simulated stomach conditions and < 1 and 63% under simulated duodenal conditions. Notably, these large differences in metal bioaccessibility were independent of equilibrium solubility and stability constants. Instead, the relationship (stomach phase R = 0.927; duodenum phase R = 0.891) between bioaccessibility and water exchange rates of metal cations (k(H₂O)) indicated that desorption kinetics may influence if not control metal bioaccessibility.

Polycyclic aromatic hydrocarbons are enriched but bioaccessibility reduced in brownfield soils adhered to human hands

The health risk associated with exposure to urban brownfields is often driven by the incidental ingestion of soil by humans. Recent evidence found that humans likely ingest the fraction of soil that passes a 45-microm sieve, which is the particle size adhered to the hands. We evaluated if PAH concentrations were enriched in this soil fraction compared to the bulk soil and if this enrichment lead to an increase in bioaccessibility and thus an increase in incremental lifetime cancer risk for exposed persons. Soils (n=18) with PAH concentrations below the current Canadian soil quality guidelines for human health were collected from an Arctic urban site and were sieved to pass a 45-microm sieve. Soil PAH profiles were measured and bioaccessibility was assessed using the Simulator of the Human Intestinal Microbial Ecosystem (SHIME). PAHs were significantly enriched in the <45 microm size fraction (3.7-fold) and this enrichment could be predicted according to the fugacity capacity of soil (Enrichment=2.18-0.055Zsoil, r2=0.65, p<0.001). PAH release in the stomach and small intestine compartments of the SHIME was low (8%) and could not be predicted by PAH concentrations in 45-microm sieved soil. In fact, PAH release in the SHIME was lower from the <45 microm size fraction despite the fact that this fraction had higher levels of PAHs than the bulk soil. We postulate that this occurs because PAHs adsorbed to soil did not reach equilibrium with the small intestinal fluid. In contrast, PAH release in the colonic compartment of the SHIME reached equilibrium and was linked to soil concentration. Bioaccessibility in the SHIME colon could be predicted by the ratio of fugacity capacity of soil to water for a PAH (Bioaccessibility=0.15e(-6.4x10E-7Zsoil/Zwater), r2=0.53, p<0.01). The estimated incremental lifetime cancer risk was significantly greater for the <45 microm soil fraction compared to the bulk fraction; however, when bioaccessible PAH concentrations in a simulated small intestine were used in the risk assessment calculations, cancer risk was slightly lower in the <45 microm soil fraction for these soils. Our results highlight the importance of using a small soil size fraction, e.g. 45 microm, for contaminated site human health risk assessment. However, further work is needed to estimate the bioavailability of this size fraction in an in vivo model and to assess the correlation between in vitro and in vivo gastrointestinal models.

The effect of residence time and fluid volume to soil mass (LS) ratio on in vitro arsenic bioaccessibility from poorly crystalline scorodite

Percent arsenic bioaccessibility is occasionally dependent upon arsenic concentration; however, the mechanism(s) of this relationship has not yet been defined. To evaluate the mechanism of this relationship, the arsenic bioaccessibility from freshly synthesized poorly crystalline scorodite was measured in the stomach, small intestine, and colon stages of the Simulator of the Human Intestinal Microbial Ecosystem (SHIME). The shape of the arsenic dissolution isotherms were different between stages (stomach: linear; small intestine: exponential rise to maxima; colon: sigmoidal). These results indicate that arsenic bioaccessibility may be limited by either in vitro GI fluid saturation or in vitro GI model residence time, depending upon the chemical/microbiological conditions of the model. Gastrointestinal microorganisms increased arsenic bioaccessibility of scorodite up to two-fold in the SHIME colon; however, this was dependent upon the sample arsenic concentration. Up to 40% of the bioaccessible arsenic was reduced to arsenite; however this process was neither mediated by GI microorganisms nor associated with increased arsenic bioaccessibility.

Nutritional status and gastrointestinal microbes affect arsenic bioaccessibility from soils and mine tailings in the simulator of the human intestinal microbial ecosystem

In vitro gastrointestinal models, used to measure the metal(loid) bioaccessibility for site specific risk assessment, are typically operated under fasted conditions. We evaluated the hypothesis that fed conditions increase arsenic bioaccessibility on three reference soils (NIST 2711, NIST 2709, and BGS 102) and the bulk and <38 mum size fractions of a mine tailing. The three nutritional states included a fed state with a carbohydrate mixture, a second fed state with homogenized crowberries (Empetrum nigrum), and a fasted state. The carbohydrate mixture increased arsenic bioaccessibility from four of five samples in the simulator of the human intestinal microbial ecosystem (SHIME) stomach but only three of five samples in the SHIME small intestine and colon. In contrast, crowberries increased arsenic bioaccessibility from four of five samples in the SHIME small intestine but had variable affects in the SHIME stomach and colon. The effect of nutritional status on arsenic bioaccessibility was potentially mediated via ligand-promoted dissolution in the SHIME stomach and small intestine. The displacement of arsenic with phosphate was potentially present in the SHIME small intestine but not the SHIME stomach. Microbial activity increased arsenic bioaccessibility relative to sterile conditions from four of five samples under fasted conditions and three of the five samples under fed conditions, which may suggest that in vitro gastrointestinal (GI) models operated under fed conditions and with microbes provide a more conservative estimate of in vitro bioaccessibility. However, for some samples, the arsenic bioaccessibility in the SHIME colon (with microbial activity) was equivalent to values observed in a separate physiologically based extraction test under small intestinal conditions (without microbial activity). These results suggest that the incorporation of microbial activity into in vitro GI models does not necessarily make estimates of arsenic bioaccessibility more protective than those generated using in vitro models that do not include microbial activity.

Bioaccessibility of mercury from traditional northern country foods measured using an in vitro gastrointestinal model is independent of mercury concentration

Human health risk assessment of dietary mercury (Hg) exposure in Canada assumes that all Hg from fish consumption is in the form of methylmercury (MeHg), the more bioavailable and hazardous form of Hg. In contrast, the risk assessment of dietary Hg to Inuit in northern Canada assumes that no more than two-thirds of dietary Hg is MeHg since mammal organs consumed by Inuit contain substantial concentrations of inorganic Hg. In vitro gastrointestinal models (e.g., the Simulator of the Human Intestinal Microbial Ecosystem) are often used for the evaluation of soil contaminant bioaccessibility, i.e., the fraction solubilized into gastrointestinal fluids, for use in site-specific human health risk assessment. In this research, we digested northern country foods using the SHIME for the measurement of Hg bioaccessibility, a novel approach for the assessment of dietary Hg bioavailability. We demonstrated that small intestinal Hg bioaccessibility from 16 fish, wild game, and marine mammal samples consumed by Inuit in northern Canada ranged between 1 and 93% and was independent of food HgT (MeHg+Hg(II)) concentration. Additionally, we demonstrated that gastrointestinal microbes may affect Hg bioaccessibility of the 16 country foods, either increasing or decreasing bioaccessibility depending upon the type of food. These results indicate that gastrointestinal absorption of Hg is not likely limited by the concentration of Hg in the food, which is in agreement with in vivo Hg bioavailability studies. Furthermore, these in vitro results support the hypothesis that the gastrointestinal absorption of Hg from Inuit country foods is dependent upon food type.

Toxicity and hazard of a mixture of SSRIs to zooplankton communities evaluated in aquatic microcosms

The toxicity and hazard of a mixture of selective serotonin reuptake inhibitors (SSRIs), including fluoxetine, fluvoxamine, and sertraline, to zooplankton communities were evaluated using 120,00l outdoor microcosms. Acute (day 4) and chronic (day 35) zooplankton abundance and species richness were assessed for Rotifera, Cladocera, and Copepoda. For acute SSRI exposures, rotifers were the most sensitive zooplankton taxa to changes in abundance (predicted no effect concentration (PNEC)=19 nM); however, no effects in zooplankton species richness were observed for this treatment period. A decrease in Copepoda abundance and species richness was observed following chronic exposures of SSRIs (PNEC=9.1 nM). A 99th-centile predicted environmental concentration (PEC=0.51 nM) yielded HQs at least two orders of magnitude below 1. Therefore, mixtures of SSRIs do not appear to present a hazard to zooplankton communities at environmentally relevant concentrations.

Gastrointestinal microbes increase arsenic bioaccessibility of ingested mine tailings using the simulator of the human intestinal microbial ecosystem

It is widely accepted that the use of total metal concentrations in soil overestimates metal risk from human ingestion of contaminated soils. In vitro simulators have been used to estimate the fraction of arsenic present in soil that is bioaccessible in the human digestive track. These approaches assume that the bioaccessible fraction remains constant across soil total metal concentrations and that intestinal microbiota do not contribute to arsenic release. Here, we evaluate both of these assumptions in two size fractions (bulk and <38 microm) of arsenic-rich mine tailings from the Goldenville, Lower Seal Harbour, and Montague Gold Districts, Nova Scotia. These samples were evaluated using an in vitro gastrointestinal model, the Simulator of the Human Intestinal Ecosystem (SHIME). Arsenic bioaccessibility, which ranged between 2 and 20% in the small intestine and 4 and 70% in the colon, was inversely related to total arsenic concentration in the mine tailings. Additionally, arsenic bioaccessibility was greater in the bulk fraction than in the <38 microm fraction in the small intestine and colon while colon microbes increased the bioaccessibility of arsenic in mine tailings. These results suggest that the practice of using a constant percent arsenic bioaccessibility across all metal concentrations in risk assessment should be revisited.