Argument: Oil sands are one of the dirtiest fuels available
"Canada's energy industry. Tarred with the same brush." The Economist. Aug 5th 2010: "Canadian crude is dirty. Just over half the country’s oil comes from tar sands, a mixture of water, sand, clay and bitumen—an extremely dense and thick form of petroleum, which usually must be melted before it can be extracted and refined."
Henry Waxman, chairman of the House Committee on Energy and Commerce, calls it “the dirtiest source of transportation fuel currently available”