"While the Koch brothers admit to not being experts on the matter, these billionaire oil tycoons are certainly experts at contributing to climate change. That's what they do very well. They are one of the main causes of this. Not a cause, one of the main causes," Reid said on the Senate floor.
"The University of Massachusetts, Amherst ... ranked Koch Industries as one of the nation's biggest air and water polluters, period," he said, adding: "They are the champions."
In August 2013, the university's Political Economy Research Institute listed Koch Industries as one of the largest polluters, behind publicly traded corporations like ExxonMobil and Dow Chemicals, among others.
This article has been updated for clarity.