Electric cars aren't just for the coasts anymore.

Colorado took its first step Thursday toward becoming the 10th state to follow California's zero-emissions vehicle mandate, which would require automakers to sell electric cars there.

At an event where he rolled up in an electric car, Colorado's Governor Jared Polis signed an executive order aimed at adding reducing emissions in the state. The order, among other things, directs the Colorado Department of Public Health to study and report to a committee by May how to increase ZEV adoption in the state. The committee is likely to recommend following California's zero-emissions vehicle mandate, which would require up to 9 percent of the cars sold in the state by 2025 to be electric, or fuel-cell vehicles.

Last year, Colorado was the first Rocky Mountain state to fully adopt California's stricter emissions standards, but stopped short of adopting the ZEV mandate. (New Mexico agreed to adopt California's emissions standards in 2007, but never implemented them.)

The move for more ZEVs would make Colorado the second non-coastal state, after Vermont, to require electric-car sales.

DON'T MISS: Colorado moves to follow California's low-emissions air-quality rules

Under the Clean Air Act, California has a special exemption to set its own emissions standards, because its original standards predated the existence of the EPA. Other states cannot set their own emissions standards, and by default have to abide by the EPA standards, but they can choose to follow California's stricter standards instead.

Since California's ZEV mandate is a separate standard from its emissions rules for internal combustion cars, states can sign on to the smog rules without agreeing to electric-car mandates or choose both.

READ THIS: California and 16 states sue EPA over emissions rules

Since electric cars have no tailpipes and use far less energy than gas cars, it's easier for states to clean up their air quality by imposing restrictions on a few local power plants and by building renewable energy installations if residents drive electric cars than it is to make millions of gas engines cleaner.

Twelve states plus Colorado have signed on to follow California's tailpipe standards, though only nine have adopted the zero emissions vehicle mandates.

READ MORE: Trump administration releases proposal to weaken fuel economy, emissions standards

Under the Trump administration, the EPA has introduced proposals to loosen emissions standards on power plants, freeze rising fuel-economy standards that were coordinated with California under the Obama administration, and rescind California's right to set its own standard.

Before those proposals were even released, 16 states, not including Colorado, sued the EPA claiming that the proposals are illegal.

In the midst of the the partial government shutdown that affected the rest of his agency, EPA Acting Administrator Andrew Wheeler was on Capitol Hill Thursday in confirmation hearings to become the agency's permanent administrator. In hearings before the Senate Environment and Public Works Committee, Wheeler defended his record of deregulation at the EPA. “Through our deregulatory actions, the Trump administration has proven that burdensome federal regulations are not necessary to drive environmental progress,” he said.