PAHs are released during the process of extracting petroleum from the oil sands. Environmental Impact Assessments have so far only considered the PAHs that are released directly into the atmosphere. The risk associated with those direct releases was judged to fall within acceptable regulatory limits.

 

The model used by Parajulee and Wania takes into account other indirect pathways for the release of PAHs that hadn’t been assessed before or were deemed negligible. For instance, they found that evaporation from tailings ponds – lakes of polluted water also created through oil sands processing – may actually introduce more PAHs into the atmosphere than direct emissions.

“Tailings ponds are not the end of the journey for many of the pollutants they contain. Some PAHs are volatile, meaning they escape into the air much more than many people think,” says Parajulee. (pictured seated at right with Wania).

The higher levels of PAHs the UTSC scientists’ model predicts when accounting for emissions from tailings ponds are consistent with what has actually been measured in samples taken from areas near and in the Athabasca Oil Sands Region. 

The authors also found, however, that tailings ponds emissions are likely not significant contributors of relatively involatile PAHs to the Oil Sands Region atmosphere. Instead, other emissions sources not taken into account by the environmental impact assessment, such as blowing dust, are probably more important for these chemicals. 

The pair of researchers modeled only three PAHs, which they believe are representative of others. Still, they say, their model indicates better monitoring data and emissions information are needed to improve our understanding of the environmental impact of the oil sands even further. 

“Our study implies that PAH concentrations in air, water, and food, that are estimated as part of environmental impact assessments of oil sands mining operations are very likely too low,” says Wania. “Therefore the potential risks to humans and wildlife may also have been underestimated.”