Utah officials celebrated a groundbreaking Tuesday for Utah’s first Tier 3-compliant oil refinery, but the event highlighting cleaner fuels was overshadowed by concerns over a Trump administration proposal to roll back U.S. emissions standards for new vehicles.

Utah Gov. Gary Herbert, the head of the Utah Department of Environmental Quality (DEQ) and other dignitaries praised oil refiner Andeavor, formerly Tesoro, for its decision to begin producing the cleaner-burning Tier 3 vehicle fuels for local markets at its Salt Lake City refinery.

“They are leading the way, and others will follow,” Herbert said during Tuesday’s groundbreaking ceremony.

Tier 3 refers to a set of federal vehicle emission standards that took effect in 2017, requiring more effective pollution-control equipment on new vehicles, but also limiting how much sulfur gasoline can contain. High levels of sulfur can reduce the efficiency of vehicle emissions systems, causing cars to pollute more.

Those standards do not require all oil refineries to produce the cleaner fuels, but Utah elected to offer tax breaks to companies to produce and distribute Tier 3 fuels in the state. And at Tuesday’s groundbreaking, Herbert recalled meeting with executives from each of the state’s refineries, asking them to “do the right thing” for the community and air quality.

Tier 3 fuel has the potential to reduce vehicle emissions of some pollutants by 80 percent, Herbert said — the equivalent of taking 4 out of every 5 cars off the road in a state where nearly half of all emissions come from vehicles.

Alan Matheson, head of state DEQ, said that “as the husband of a wife with respiratory problems, and as a father … I just want to say thank you to Andeavor.”

“This really makes a difference,” Matheson said.

He called on Utahns to seek out the cleaner fuels as they become available at filling stations around the state, as well as purchasing the cleanest vehicles they can afford.

A spokesperson for Andeavor said they expect to be selling the slow-sulfur gasoline by mid- to late 2019. Andeavor sells fuel under the brands Shell, Exxon and Tesoro.

Matheson also touted other successes in reducing Utah’s emissions, which he said have declined in the face of rapid population growth, amounting to 46 percent less pollutants per resident since 2002.

After the groundbreaking, however, Matheson expressed concern about the Trump administration’s signals that it intends to pare back standards for vehicle emissions put in place under President Barack Obama.

“The rollback,” Matheson said, “will add to the challenges of meeting air quality standards.”

Utah is still drafting a new plan for how it will meet the U.S. Environmental Protection Agency’s limits on small particulate pollution, which can build up during inversions on the Wasatch Front. Some parts of the state have violated that EPA standard for more than a decade.

But it’s unclear, Matheson said, what impact the federal rollback could have on Utah, and he said he was waiting to get the details on which standards might be affected.

The impact to Utah will be lessened if Trump officials target standards that require automakers to produce more fuel-efficient vehicles, but leave limits on emissions intact.

And if the EPA opts to revise the Tier 3 standards, Matheson said, Utah will struggle to persuade other refineries to follow Andeavor’s example — something the state is banking on in order to clean up its air.

While cuts to the fuel efficiency standards seem guaranteed, Michael Shea, a policy associate for the clean-air advocacy group HEAL Utah, said there are concerns that other standards could be affected.

Federal regulations have played a key role in emissions reductions touted by Herbert and his staff, Shea said. And even if the rollback is limited to fuel-efficiency standards, he said, that could increase pollution in Utah.

Historically, Shea said, Utahns tend to buy larger, more polluting vehicles when gas prices are low. Without a strict legal mandate, he warned, automakers will feel less pressure to make these large vehicles more efficient, resulting in more gasoline burned — and more pollution.