Modeling and Measuring Environmental Contaminant Exposure Among Canadian Arctic Indigenous Humans and Wildlife
Keywords: Human pollutant exposure
Indigenous Arctic populations
Marine mammals
Mechanistic modeling
Persistent organic pollutants
Traditional food

Arctic wildlife and indigenous human exposure to persistent organic pollutants (POPs) was mechanistically simulated using a combined global fate and transport model (GloboPOP) and food chain bioaccumulation model (ACC-Human Arctic) approach. Initial model results demonstrated that POP concentration-age relationships in long-lived Arctic marine mammal (MM) populations (ringed seals, beluga whales, bowhead whales) are not equivalent to those in individuals when assuming realistic, time-variant chemical emissions. Birth year relative to peak emissions year was the most critical parameter differentiating population versus individual concentration-age associations, while lifespan was shown to possess a negligible impact when these trends were controlled for the birth year effect. Additionally, birth year influence was essentially mitigated in reproductive female Arctic MMs, due to the appreciable POP elimination potential of lactation. Reproductive female wildlife retained no â memoryâ of past POP exposure, and therefore in certain instances population versus individual concentration-age trends were similar. Applying this model approach to reproduce measured POP exposures among indigenous Arctic humans revealed that reported rates of traditional food (TF) consumption, particularly of lipid-rich MM items, were critical determinants of modeled POP concentrations, while their association with measured levels was generally much weaker. This discrepancy in the contribution of reported TF consumption to modeled versus measured POP concentrations caused our model to appreciably overestimate exposures among certain Arctic indigenous biomonitoring populations, to a degree that suggested TF intake rates were highly uncertain. Given this, no reasonable conclusions were possible regarding the chief theorized determinants to temporal POP exposure trends in these groups, namely declining environmental concentrations and reduced population-wide TF consumption. The effect of temporary changes to TF intake by indigenous Arctic women of childbearing age (WCBA), as well as fish intake by temperate WCBA was also investigated. Reductions in consumption of these critical dietary POP exposure sources, including even complete elimination for multiple years prior to pregnancy, was ineffective in reducing long-lived POP exposure to WCBA and their offspring, as WCBA still retained significant body burdens from earlier exposure. However, greater consumption of these same items was shown to rapidly increase POP levels beyond regulatory thresholds. Finally, field and experimental analysis of beluga blubber TFs illustrated that food preparation techniques can exert a significant influence on the levels of certain nutrients and environmental contaminants in these food items. Ageing beluga blubber was the most impactful process examined, due to its distinctive phase separation between solid fat and liquid oil after sufficient fermentation time. Aged liquid oil contained elevated levels of beneficial polyunsaturated fatty acids, and phase separation also selectively depleted certain hydrophilic contaminants from the liquid oil, such as mercury and several ionogenic perfluorinated pollutants. Though ageing uqsuq did not in turn raise concentrations of many hydrophobic contaminants, we did observe elevated concentrations of polycyclic aromatic hydrocarbons, which ultimately suggested that TF preparation methods may not only modulate chemical content present prior to food processing, but in fact introduce contaminants. Ultimately, our findings aligned with previous investigations of food preparation influence on nutrient and contaminant levels by demonstrating widely variable effects from processing, depending on the compounds, foods, and techniques examined. We also suggest that uqsuq oil may be the most appropriate beluga blubber TF product for indigenous Arctic Canadians wishing to maximize nutrient intake from these food items while minimizing environmental contaminant exposure.