New scientific research has found increased levels of some carcinogenic chemicals linked to oil sands mining in the Athabasca River, refuting long-held industry and government claims that natural sources are responsible for the pollutants.
The chemicals, called polycyclic aromatic hydrocarbons (PAHs), have been shown to cause cancer in laboratory animals as well as other health problems.
PAH concentrations in Athabasca River sediments located downstream of oil sands projects increased 41 percent between 1999-2009, according to , published earlier this month in the journal Environmental Science and Technology.
Kevin Timoney, principal investigator at the consulting firm Treeline Ecological Research and lead author of the study, said the rise parallels the growth in oil sands production in the lower Athabasca region, which more than doubled between 1998 and 2009.
Alberta's oil sands deposits represent the second-largest petroleum reserve in the world after Saudi Arabia's. In 2009, Canada exported about 950,000 barrels of oils sands crude a day to the United States, nearly 80 percent of the roughly 1.2 million barrels that are extracted daily from the province. Production is expected to more than double during the next five years.
It takes a lot of energy and water to extract bitumen, the tar-like viscous type of crude oil that is buried in the province's sand and clay. Scientists have been particularly concerned about the effects of harvesting the fuel on the Athabasca River, the largest free-flowing river in Alberta.
The 956-mile waterway flows northeast through most of Alberta's tar sands mines before draining into Lake Athabasca.
PAHs Already at Harmful Levels
PAHs are found naturally in bitumen, but mining activities can increase exposure of the hydrocarbons to air and water. Processing the bitumen into synthetic crude releases additional PAHs into the environment.
In the lower Athabasca River, PAH concentrations in sediment have already reached a level that's harmful to aquatic life, Timoney told SolveClimate News in an interview.
Government and industry sources have long insisted that the contamination stems from naturally occurring bitumen instead of mining activity.
The official states, "There is no doubt that PAHs are in the sediments downstream of the oil sands. This is due to the magnitude of the oily sand along the river banks through which the river has eroded naturally ... The sources in the area are natural."
Timoney said this "misinformation" is what inspired him to test the government's claims. "I decided to sit down with a colleague and pull all of the relevant data together — which has never been done before — and ask, 'What is the situation? Are PAHs changing and why?'"
While the scientists found increasing PAH levels in sediment downstream of the mines, the same trend was not found at control sites upstream of tar sands operations.
Their research joins a growing number of independent, peer-reviewed studies showing the industry's harmful effects on the Athabasca River Basin.
Two years ago, scientists measured of dissolved PAHs in waters near oil sands upgrading facilities. Last year, a separate found elevated concentrations of heavy metals — including mercury, copper and lead — downstream of mining. Both studies were published in the journal Proceedings of the National Academy of Sciences.
'Urgent Health Study' Needed
PAHs accumulate in sediment and make their way up the food chain through aquatic life. While some PAHs are known human carcinogens, there is still little research on the toxicology of most PAH compounds found in bitumen, said Timoney.