Human Health Risks of Persistent Organic Pollutant Exposures in the Canadian Arctic

• Main Author: Singh, Kavita
• Format: Thesis
• Language: English
• Published: Université d'Ottawa / University of Ottawa 2018
• Subjects: Arctic; Persistent Organic Pollutant; Risk Assessment; Human health; inuit
• Online Access: https://dx.doi.org/10.20381/ruor-22061; http://ruor.uottawa.ca/handle/10393/37799

The persistent organic pollutants (POPs) refer to many different chemicals that, upon release into the environment, remain intact for several decades. These contaminants travel long distances through repeated cycles of deposition and evaporation, and eventually deposit in the Arctic regions. The purpose of this work was to examine the potential human health implications of POP exposures among the Canadian Inuit, using modelling and epidemiological approaches. Blood guideline values were developed for the organochlorine pesticides, chlordane and toxaphene, and the polychlorinated biphenyls (PCBs) using the concept of biomonitoring equivalents (BEs), which are based on toxicity endpoints and toxicokinetic modelling to convert an oral reference dose to an equivalent blood concentration. The biomonitoring data from the Adult Inuit Health Survey (2007-2008) and the Canadian Health Measures Survey (CHMS, Cycle 1 2007-2009) were compared with the derived guideline values to assess population-level risks of exposures for the Inuit and the general Canadian population, respectively. Epidemiological analyses were also conducted to explore if POPs were associated with diabetes and high cholesterol, using data from the Inuit Health Survey. A set of BE values were derived for chlordane isomers and metabolite, three abundant toxaphene isomers, and the PCBs. The derived values are in a similar range of the BEs of other POPs in the literature. Among the Inuit, a large percentage exceeded the trans-nonachlor guideline value, particularly among the elderly. Fewer exceedances were observed for cis-nonachlor and oxychlordane, none for toxaphene, and minimally for the PCBs. In comparison, no exceedances for any of the POPs were observed in the general Canadian population. Highest vs. lowest quartile exposures to PCBs and p,p’-DDE were associated with increased risk of diabetes and an increase in fasting glucose among the Inuit. In addition, PCBs were associated with increased risk of high cholesterol, and higher levels of serum triglycerides, total cholesterol, and low-density lipoprotein cholesterol (LDL-C), but not high-density lipoprotein cholesterol (HDL-C). The results of this work suggest that exposures to POPs remain a potential health concern among the Canadian Inuit. Future research efforts should be devoted to collecting updated contaminant concentrations for the Inuit, measuring contaminants in prepared food samples, conducting cohort studies on contaminant exposures and health outcomes, and assessing the effects of chemical mixtures using statistical approaches and toxicokinetic modelling.