A handful of new pollution-control ideas — and a few old ones — have drawn initial approval on Utah’s Capitol Hill, though some state lawmakers remain dubious the added steps are needed.

Four air-quality bills advanced through committee this week in the 2018 Legislature, most of them focused on reducing emissions from diesel vehicles.

But several are likely face an uphill battle in the weeks remaining before the session’s March 8 adjournment. Most of the measures have drawn complaints from skeptical lawmakers, some of whom questioned whether their benefits outweighed the costs.

HB101 seeks to extend diesel-emissions testing after a similar measure failed last year in the face of opposition from Utah County, the only county in the state that tests gasoline-powered cars but not those with diesel engines

Sponsoring Rep. Patrice Arent, D-Millcreek, said this year she has Utah County’s support, after modifying the legislation to request that county officials put in place a three-year pilot program for testing, instead of requiring it.

But HB101 still met opposition on Tuesday, with lawmakers questioning whether the additional testing for pollutants was necessary.

“Every vehicle that you buy nowadays is 100 percent pollution free,” said Rep. Mike Noel, R-Kanab, who added that he recently bought a new 2016 diesel truck. He also noted the state’s success in convincing areas refineries to produce cleaner-burning Tier 3 fuels, which he said would be of greater benefit to air quality than testing more trucks.

“We should be spending our money first on those issues that have the best cost-benefit … and I think that’s the Tier 3 fuels,” Noel said. “If we’re moving toward Tier 3 fuels, I think we’re premature on this issue and we don’t have to do this right now.”

But environmentalists, state regulators and officials with the Andeavor Refinery in Salt Lake City, formerly Tesoro, all testified that for Utah to benefit from Tier 3 fuels, it would have to ensure that vehicles are operating properly.

Counties that already test diesel vehicles have found that roughly 20 percent of light- and medium-duty diesel trucks fail emissions standards, Arent testified, making them 2 to 3 times more likely to fail than gasoline-powered vehicles.

Over a third of diesel trucks that failed had been illegally modified to produce more pollution, she said.

“New vehicles should operate cleanly,” Bryce Bird, director of the state Division of Air Quality, later testified. “But smart people get around it.”

The House Natural Resources, Agriculture and Environment committed voted unanimously in favor of HB101. Noel did not participate in the final vote, having left the meeting early.

Later in the day, a similar scenario played out when Rep. Stephen Handy, R-Layton, presented a bill to address air pollution caused by diesel emissions from locomotives.

HB211 would create a state program of issuing grants to railroads that want to upgrade emissions controls on their freight switchers, the locomotives that ferry cars around rail yards before they’re shipped across all over the country.

Utah has about 60 of these freight switchers in operation, Handy testified, and most operate around the clock.

Glade Soward, a policy analyst for the state Division of Air Quality, testified the freight switchers emit about 8.8 tons a year of small particulates, the pollutant closely tied to the Wasatch Front’s winter inversions. They also emit 400 tons of nitrogen oxide a year, which scientists believe helps to create even more particulate pollution in Utah’s atmosphere.

Updating train engines would cut those emissions by nearly 90 percent, Soward said, but at a cost between $1.5 million and $2 million per locomotive.

Reps. Carl Albrecht, R-Salt Lake City, and Doug Sagers, R-Tooele, raised concerns when Soward mentioned that 49 of Utah’s freight switchers are owned and operated by the Union Pacific Railroad, which Handy said helped to draft HB211.

Omaha-based Union Pacific had a net revenue of $4.2 billion in 2016, Sagers said. “That’s almost our entire general fund,” he said. “Could you tweak the bill to make it more cost effective?”

Handy said he was open to amendments to HB211 in order to secure state funds for a pilot program to clean up rail-yard emissions, which witnesses testified have a disproportionate effect on the health of Utah’s low-income and minority residents.

Emissions measured at one rail yard on Salt Lake’s west side were as high as those from I-15, according to testimony from Daniel Mendoza, a post-doctoral fellow from the University of Utah.

“It was comparable to the most busy highway in Utah,” Mendoza said.

The House Natural Resources committee voted 10-1 in favor Handy’s bill, with the lone opposing vote coming from Rep. Albrecht. Reps. Noel and Sagers were not present for the vote.

Two other bills have also made it through their first committee hearings. The House Transportation Committee voted unanimously in favor of HB 331, which would add instructional materials on preventing air pollution to Utah’s driver-education curriculum.

And HB171, which would double the state’s current $50 penalty for driving a diesel vehicle that does not comply with federal emissions standards, was also passed favorably by the same committee last Friday, with a vote of 6-1.