Seeking the Source: Dioxin Exposure Levels and Determinants and Fluoroalkyl Substance Determinants in Arctic and Subarctic Communities within Canada

Abstract

Abstract Background Dioxins, furans, and non-ortho dioxin-like polychlorinated biphenyls (PCBs), and per- and poly- fluoroalkyls (PFAS) are persistent toxic chemicals that have been detected in areas far from known emission sources. Following biomonitoring projects conducted in the Dehcho Region, Northwest Territories (2016-2018) and Old Crow, Yukon Territory (2019), elevated levels of PFNA were detected, and dioxins, and like-congeners were yet to be investigated. This thesis reports on dioxin exposure levels and identifies determinants that may influence dioxin and PFAS exposures in the study areas. Research Questions To assess dioxin, furan, and non-ortho dioxin-like PCB exposures, two research questions are raised: What are the levels of dioxins in blood plasma samples from Old Crow and how do these compare to the general population of Canada? and are there specific demographic variables that are associated with higher or lower exposure? The determinants of exposure are then explored among the participating communities with dioxin and PFAS exposure measures: Are there lifestyle factors or traditional foods consumption patterns that are associated with biomarkers of these analytes? Methods Biobanked plasma samples (n=54) from Old Crow were analyzed for dioxins, furans, and non-ortho dioxin-like PCBs. Data from surveys on traditional food consumption and lifestyle factors were collected in Old Crow and the Dehcho Region. Descriptive statistics were used to quantify differences in exposure between the Old Crow and Canadian Health Measures Survey (CHMS) data, then simple linear regression and multiple variable regression was used to identify the traditional foods and lifestyle factors that may influence PFAS, and dioxin and dioxin-like congener exposures. Results Most dioxins, furans, and non-ortho dioxin-like PCB exposures were lower, or similar in the study areas in comparison to the respective levels in the general population of Canada. Like the previous findings with PFNA, PCB 169 levels appeared to be approximately two fold elevated in Old Crow participants aged 20 to 39 years and 60 to 79 years when compared to the general population of Canada. The investigation of exposure determinants revealed that traditional foods were generally negatively associated with PFAS exposures, indicating that those who consumed traditional foods may have eaten fewer processed and packaged foods. However, some exceptions to this were observed. For example, PFNA exposure was positively associated with consumption of some moose tissues in Old Crow, while whitefish eggs, Canada goose meat, lake trout, and ptarmigan showed similar directionality and significances of association in the Dehcho Region. Unexpectedly, height was positively associated with PFOA, PFOS, and PFHxS levels in the Dehcho Region, but this association was not consistent with the same variable in Old Crow. Determinants analysis among dioxins and dioxin-like congeners showed different trends; PCB 126 was positively associated with multiple foods across categories. Coho salmon was significantly positively associated with exposures to 1,2,3,6,7,8-HxCDD, 2,3,4,7,8-PeCDF, and PCB 126. PCB 169 exposure was significantly positively associated with employment in an occupation of risk. It is notable that some traditional foods appeared to be associated with some persistent organic pollutant exposures; however other aspects of health, such as culture, social, and nutritional benefits were also considered in the interpretation of the results. The processes that surround the harvesting, preparation, consumption, and sharing of traditional foods promote physical activity, spiritual well-being, and socialization. It is concluded that the benefits of eating traditional foods continue to outweigh the risks of environmental contaminant exposures in the researched communities.

Contribution Regional partners and community representatives were included in developing the contextualization, interpretation, and communication of the results synthesized in this thesis. The results from these investigations were provided to the respective study participants, participating communities, and governments through an in-community meeting (e.g., Vuntut Gwitchin Research Round-up), personalized biomarker results letters, and infographic flyers. Knowledge sharing in Old Crow led to continued development of community questions surrounding local sources of contamination, and knowledge that may be applied to further investigate the sources of persistent organic pollutant (POP) exposures, potentially empowering communities to enact local policy, and reduce population exposures to contaminants. Aggregate results have been shared with researchers (e.g., the International Society of Exposure Science Conference (Chicago, 2023) and publications, according to processes outlined in community research agreements. Research on POP exposures in inland First Nations across the territories has been limited. Nationally, these results help to inform peoples’ exposures to POPs and the exposure sources among Indigenous communities located in Arctic and subarctic areas within Canada. These results are in alignment with the research priorities of the Northern Contaminants Program (Canada), Arctic Monitoring and Assessment Programme (AMAP), and Stockholm Convention which continue to monitor the levels and exposure patterns of persistent organic pollutants. This thesis has analyzed data and information from Indigenous communities that have not been represented in national biomonitoring studies. Through the biomonitoring studies and analyses conducted prior to, and in parallel with this thesis, several data gaps regarding environmental exposures in northern Indigenous populations have been filled, addressing inequities in baseline exposure information, and understanding of the potential determinants of exposure. This approach aims to enhance understandings of environmental contaminant exposures among First Nations living in participating regions while also empowering communities with local environmental health data that complements Traditional Knowledge.