Evaluating the concentrations of mercury, priority pollutant trace elements, and polycyclic aromatic compounds in traditionally harvested plant and animal foods of the Bigstone Cree Nation in Alberta, Canada

Traditional foods consumed by Indigenous communities consist of locally-harvested, nutrient-dense animal and plant species. These foods are associated with social, health, and economic benefits for the Indigenous communities, and have often been shown to have higher nutritional value than store-bought foods. Nevertheless, these foods may also contain environmental contaminants. In particular, research in Alberta has shown that the oil sands industry releases elevated levels of multiple essential and non-essential trace elements, considered as priority pollutant elements (PPE), as well as a group of organic pollutants including polycyclic aromatic compounds (PACs) in abiotic matrices such as rivers, soils, sediments, and snowpacks. Thus, release of these contaminants from the oil sands industry into the environment is a concern in local and scientific communities. There has been limited research focusing on measuring these contaminants and nutrients in wild plants, animals, and in animal organ tissues, all of which are consumed as traditional foods by Indigenous communities, including the Bigstone Cree Nation, who are living in close proximity to the oil sands developments in Alberta. The overall objective of this thesis is to determine and compare concentrations of key contaminants and nutrients (can also be toxic if consumed/accumulated in excess) in various food groups (plants and animals, and animal organ tissues) of traditional importance to the Bigstone Cree Nation. The specific objectives are addressed in three chapters: (1) determining the concentrations of total mercury (THg), methylmercury (MeHg), selenium (Se)— thought to protect against Hg toxicity—, and ratios of selenium to mercury (Se:THg) in a comprehensive suite of traditional foods of the Bigstone Cree Nation (Chapter 2); (2) investigating the concentrations of essential and non-essential PPE such as arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), nickel (Ni), silver (Ag), thallium (Tl), and zinc (Zn) in a variety of traditional food samples, including multiple plants and animal tissues/organs (Chapter 3); (3) quantifying various classes of PACs including the 16 U.S. EPA priority polycyclic aromatic hydrocarbons (PAHs), alkylated PAHs, and dibenzothiophenes—sulfur-containing PACs— in these traditional plant and animal foods (Chapter 4). Results of Chapter 2 indicated that compared to the Health Canada guideline of 0.5 μg g-1 wet weight (w.w.) and 0.3 μg g-1 w.w. for THg (respectively), none of the samples exceeded the guideline limits. Selenium was in molar excess relative to Hg for all the traditional foods (Se:THg ratio >1), suggesting a potentially sufficient amount of Se associates with Hg and mitigates its toxicity. In Chapter 3, the concentrations of PPE showed variations that were dependent on species, tissue, and trace elements. In plants, concentrations of PPE declined in the following order: Zn > Cu > Ni > Cr ~ Pb > As ~ Cd > Ag ~ Tl, while in animals, the order was Zn > Cu > Cd > Cr ~ As ~ Ni ~ Pb ~ Ag (Tl was below the detection limit in all animal samples). In Chapter 4, among different classes of PACs, alkylated PAHs predominated and accounted for between 63% and 95% of total PAC (∑PAC), while the 16 U.S. EPA priority PAHs accounted for 4% to 36% of ∑PAC. The DBT levels were the lowest and only represented <1% to 14% of ∑PAC in the traditional foods. The results of this thesis indicated that at this time, levels of contaminants found in these traditional foods do not pose a public health concern. Since previous studies have already shown elevated levels of contaminants in abiotic matrices in close proximity to the Alberta oil sands developments where Indigenous communities reside, the baseline concentrations from this thesis will be useful for future comparisons of the levels of contaminants and nutrients in traditional foods collected/harvested within oil sands development regions

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