Crude oil isn't exactly clean, but environmentalists say it beats bitumen, the tar-like oil extracted from subterranean Canadian sands.
Bitumen is more corrosive and abrasive than standard crude, hence it is more prone to causing leaks in pipelines, according to a report by the Sierra Club, National Wildlife Federation, the Natural Resources Defense Council and Pipeline Safety Trust.
Oil industry representatives disagreed with the groups' report that pipes carrying bitumen have 16 times more leaks than other other pipelines. In an article by CNN Money, they said that different reporting systems result in the difference in numbers.
The Canadian oil industry also denies another Sierra Club claim that bitumen sinks in water making it harder to clean up. They say that since the bitumen is mixed with natural gas liquids, there is no proof it would be any worse than crude oil.
That said, crude oil spills have been responsible for some of the worst environmental catastrophes in history.
Imports of the petroleum precursor into the U.S. could triple from half a million barrels to 1.5 million barrels within the next decade, according to the environmental groups' report. Much of it may flow along the proposed expansion of the Keystone pipeline.