Risk of Pollutants in Northern Traditional Diets
Subsistence hunting contributes to the livelihoods of many northern and rural Canadians. Traditional diets, including fish and meat, provide food security and essential nutrition for remote communities, where store-bought diets may lack healthy alternatives. But despite these benefits, meat and fish based diets may also threaten public safety if the food is tainted.
Mountain landscapes, especially those in the north, are perceived as pristine on account of their relatively low levels of development and expansive wilderness. However, remote wildlife populations can often accumulate high concentrations of pollutants. Some persistent contaminants (including gaseous mercury) may travel long distances from their emission sources – driven by northerly winds into arctic and alpine environments, where cooler temperatures cause them to fall from the atmosphere. Other contaminants occur naturally, for instance metals originating from exposed mineral deposits. Once taken up locally by plants, these toxic compounds can be passed up the food chain, accumulating in the tissues of large mammals and threatening human populations which eat them.
To determine the potential health risks of northern traditional diets, a team of Canadian researchers measured the concentrations of metals in tissues collected from moose, caribou, Dall’s sheep, and goat harvested from the southern Mackenzie Mountains of the Northwest Territories. The study area receives relatively low subsistence hunting pressure, but local hunting outfitters frequently distribute harvested meat within neighbouring communities. Researchers found that contamination varied among species, reflecting their dietary differences. For example, mercury concentrations were highest in caribou, which feed heavily on lichen; and cadmium concentrations were highest in moose, which tend to browse on trees and shrubs. Though cadmium was considered natural in origin, concentrations were especially elevated in moose kidneys. There were no significant signs of kidney damage, indicating that moose populations were likely unaffected; however, the contaminated tissues still cause concern over their safety for human consumption. Interestingly, radioactive cesium originating from the Fukushima disaster in 2011 was detected in some tissues harvested later that same year. While cesium concentrations were low and unlikely to pose any direct health risks, these results show how quickly emissions can reach and accumulate in northern wildlife populations – and demonstrate the vulnerability of traditional diets to both local conditions and global atmospheric processes.
This is a summary article authored by Charlie Loewen. For further information, please see the original published research:
Nicholas C. Larter, Colin R. Macdonald, Brett T. Elkin, Wang Xioawa, Naomi J. Harms, Mary Gamberg and Derek C.G. Muir (2016) Cadmium and other elements in tissues from four ungulate species from the Mackenzie Mountain region of the Northwest Territories, Canada. Ecotoxicology and Environmental Safety, 132:9–17 (doi:10.1016/j.ecoenv.2016.05.018).