Colorado Governor John Hickenlooper announced Tuesday that his state would join 13 states and the District of Columbia in adopting California’s clean car emissions standards.

“Colorado has a choice,” Gov. Hickenlooper said in a statement. “This executive order calls for the state to adopt air quality standards that will protect our quality of life in Colorado. Low emissions vehicles are increasingly popular with consumers and are better for our air. Every move we make to safeguard our environment is a move in the right direction.”

Calls for Trump's climate-science denying Environmental Protection Agency (EPA) chief Scott Pruitt to resign are mounting, as the New York Times on Thursday published a detailed look at four high-ranking EPA staffers who were forced out of their jobs after objecting to Pruitt's spending habits and management of the agency.

Inside EPA, Pruitt lost the support of many long-time Trump associates, like Kevin Chmielewski, who pushed back against Pruitt's attempt to use taxpayer money on unlimited access to a private jet at a stunning $100,000 a month and $70,000 for two desks for Pruitt and his security team, one of which was to be “bulletproof.” Chmielewski was placed on unpaid administrative leave after objecting to Pruitt's plans for that luxury spending spree on the taxpayer's dime.

More than a decade ago, Bill Wehrum, then acting assistant administrator for air and radiation at the US Environmental Protection Agency, successfully fought to deny the state of California the right to set its own standards on greenhouse gas emissions from vehicles.

He is now back in the same position at Trump's EPA, and hoping to try once again to kill the California waiver.