Today, leading environmental groups and corporate campaigning organizations released an open letter to major corporations -- the biggest consumers of tar sands, the dirtiest oil on the planet -- calling on the corporations to take responsibility for the disastrous effect that lax to non-existent corporate purchasing policies are having on the climate. Check out the letter here.

Unless a company has a specific policy in place not to purchase tar sands oil, the company is in practice supporting the destructive tar sands mining industry that is polluting our water, air, communities, and climate. The letter puts companies on notice that it's time to do the right thing.

Over the past year, corporations have come under increasing public pressure to stop using tar sands oil. PepsiCo and Coca-Cola were the first among them, due to the amount of tar sands oil used to fuel the companies' massive vehicle fleets. Just Monday, people began asking the question across social media: "How much water is poisoned to produce one barrel of tar sands? Just ask Pepsi."

"Tar sands crude is the dirtiest oil on the planet. Nineteen major companies have already adopted policies not to purchase oil from tar sands, so it's high time that the rest of America's corporations follow suit," said Michael Bosse of the Sierra Club's Beyond Oil campaign. "This letter puts the biggest corporate consumers of oil on notice that there's no excuse not to invest in cleaner, more efficient fleets, and that it's simply wrong to source oil from the tar sands, which is fouling the land and water in communities across the country, from Maine to Kalamazoo to Utah."

Amanda Starbuck, the Climate Program Director at Rainforest Action Network, put it this way: "Many big corporations that sell commodities far removed from oil extraction are nonetheless enabling the nightmarish expansion of the tar sands by refusing to purge tar sands oil from their fuel supply chains. Huge companies with massive operating budgets have ample resources to ensure they are not contributing to the worst environmental disaster on Earth, and until they do so, we will consider them complicit."

With this letter, it should be clearer than ever to America's corporations that they need to take note, take a look at how PepsiCo has been dragged into the spotlight over its use of tar sands, and take action. It's time for America's corporations to step up to the plate, say no to tar sands, and move beyond oil.

-- Rachel Rye Butler, Sierra Club Beyond Oil Campaign