Researchers say emissions of potentially hazardous air pollution that were used in environmental reviews done before approving some projects did not include evaporation from tailings ponds or other sources, such as dust from mining sites.
The study, by the University of Toronto's environmental chemistry research group, looked at reported levels of polycyclic aromatic hydrocarbons (PAH) — chemicals which can be released into the air, water and soil when bitumen-rich oilsands are mined and processed.
"Our study shows that emissions of PAH estimated in environmental impact assessments conducted to approve developments in the Athabasca oilsands region are likely too low," reads the study published Monday in the U.S. journal Proceedings of the National Academy of Sciences.
"The potential therefore exists that estimation of future risk to humans and wildlife because of surface mining in the Athabasca oilsands region has been underestimated."
Professor Frank Wania, one of the study's authors, said the results highlight the need for improved accounting of PAH emissions from oilsands operations, especially when more projects are being built or planned in the region.
Using computer models, researchers studied emissions estimates from environmental reports to predict chemical concentrations from direct oilsands industrial activity such as mining, processing and vehicle traffic.
They found the levels were lower than actually measured levels of chemicals in the air recorded in other scientific studies.
Researchers then modified the computer model to factor in estimates of evaporation from oilsands tailing ponds. Predicted concentrations were then much closer to the recorded levels.
They used a third model using concentrations of PAH levels measured by Environment Canada in the region between November 2010 and February 2011.
The results suggest emissions may be two to three times higher than the estimates recorded in project environmental reviews.
Wania said some chemicals pose a potential cancer risk, but nothing imminent.
The concentrations that have been measured in the air in the oilsands region are comparable to a big city such as Toronto.
"It is not that I am raising the red flag here, that we should be very concerned, because we live with these concentrations day in and day out," he said.
"All we are saying is that the basis for the human health risk assessment is flawed."
Wania said the team's research was funded by the university. Environment Canada is providing money for more research to follow up on the findings.
A report published last year in the same journal found that oilsands development is polluting surrounding lakes in northern Alberta.
The federally funded research by some of Canada's top scientists found levels of toxic hydrocarbons in six lakes between 2 1/2 and 23 times what they were before the mines were built.
The paper said while overall toxin levels remain low, trends aren't good and some lakes are already approaching warning levels.
It said the timing of the contamination and its chemical makeup point to industrial sources.