Before: Boreal forest. After: Tar sands mine. Photo: Toban Black / flckr

By Bobby Magill
3 February 2014

(Climate Central) – One of the biggest concerns about producing crude oil from the Alberta tar sands is its impact on climate change, which has been a major part of the debate about whether the Keystone XL Pipeline should be built.

A new University of Toronto-Scarborough study published Monday says there’s another reason to be concerned about oil production in the tar sands: The Canadian government may have underestimated emissions of carcinogens known as polycyclic aromatic hydrocarbons, or PAHs, from the Alberta tar sands, and they may be a major hazard to both human and ecosystem health.

Official estimates of PAH emissions from the Alberta tar sands have been used by the Canadian government to approve new tar sands development, and estimates for PAH concentrations in air, water and food in the region may also be too low, leading to an underestimation of PAH risk to human health, the study says.

PAHs are not greenhouse gases, and have no direct effect on climate change. But their source does: The U.S. State Department in its Final Supplemental Environmental Impact Statement for the proposed Keystone XL Pipeline, released Friday, says the production and processing of a barrel of tar sands crude releases 17 percent more carbon emissions than the average barrel of crude produced elsewhere.

For anyone living along the Keystone XL Pipeline’s route, PAHs are a big deal, said Jules M. Blais, a University of Ottawa chemical and toxicology professor who is unaffiliated with the study.

“From the standpoint of Keystone, the concerns are regarding potential breaches that could contaminate soils,” he said. “The same kinds of things that are getting into the Athabasca River could be relevant to Keystone.”

PAHs, which include phenanthrene, pyrene and benzo(a)pyrene, “are among the most toxic hydrocarbons,” Blais said. “They’re some of the worst things out there.”

Previous studies have found that fish and other aquatic species are harmed when they’re exposed to oil sands water and sediments produced in the region, according to the study. Increased concentrations of PAHs are found in oil sands tailings ponds and have been found in the Athabasca River, which threads through the oil sands region.

“We found that the predictions the model uses were too low than what has been measured,” Wania said. “The officially reported emissions are very likely too low.” [more]

Tar Sands Toxins with Keystone XL Link Underestimated


ABSTRACT: Emissions of organic substances with potential toxicity to humans and the environment are a major concern surrounding the rapid industrial development in the Athabasca oil sands region (AOSR). Although concentrations of polycyclic aromatic hydrocarbons (PAHs) in some environmental samples have been reported, a comprehensive picture of organic contaminant sources, pathways, and sinks within the AOSR has yet to be elucidated. We sought to use a dynamic multimedia environmental fate model to reconcile the emissions and residue levels reported for three representative PAHs in the AOSR. Data describing emissions to air compiled from two official sources result in simulated concentrations in air, soil, water, and foliage that tend to fall close to or below the minimum measured concentrations of phenanthrene, pyrene, and benzo(a)pyrene in the environment. Accounting for evaporative emissions (e.g., from tailings pond disposal) provides a more realistic representation of PAH distribution in the AOSR. Such indirect emissions to air were found to be a greater contributor of PAHs to the AOSR atmosphere relative to reported direct emissions to air. The indirect pathway transporting uncontrolled releases of PAHs to aquatic systems via the atmosphere may be as significant a contributor of PAHs to aquatic systems as other supply pathways. Emission density estimates for the three PAHs that account for tailings pond disposal are much closer to estimated global averages than estimates based on the available emissions datasets, which fall close to the global minima. Our results highlight the need for improved accounting of PAH emissions from oil sands operations, especially in light of continued expansion of these operations.

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