SALT LAKE CITY -- Utah has been successful at reducing the number of red air days during the winter season when high pressure forces air to stagnate in valleys along the Wasatch Front and in the Cache Valley.
But red air days still come, forcing sensitive groups indoors and, at times, into emergency rooms.
The key questions: what has led to the reduction in red air days, and what will work in the future?
Follow the trend lines and the answer is pretty clear, according to Matt Pacenza, the Executive Director of the Health Environment Alliance, or HEAL, Utah.
"More than anything else what we have to thank is federal regulation," Pacenza said.
In Governor Gary Herbert's State of the State address for 2017, Herbert cited the reduction in pollutants overall and per capita in Utah.
"While Utah's population increased by more than 600,000 between 2002 and 2014, total statewide emissions declined by 30 percent," Herbert said. "That's a 46 percent reduction in per capita emissions."
Those dates and reductions in pollutants correspond with increasingly strict rules for clean fuel and clean cars mandated by the Clean Air Act.
The Environmental Protection Agency required fuel with 30 parts of sulfur per milliliter starting in 2006, and cars and trucks had to meet cleaner standards phased in from 2004 to 2009.
The Director of the State Department of Environmental Quality, Alan Matheson, talked to Fox 13 News about the state's role in the regulatory process.
"Under the Clean Air Act, there's this system that's been set up where the federal government, the EPA, sets a health-based standard for us to meet, and then it's the responsibility of the states to put together a plan and take the actions to get there," Matheson said.
Matheson and Herbert make strong statements about their commitment to clean air, but they face a headwind when it comes to political money and influence in Utah.
A Fox 13 examination of the companies regulated by the State Division of Air Quality showed that they had at least 181 active lobbyist registrations in the Utah Lobbyist Database, meaning polluting industries are active and invested in what happens at the Utah legislature.
And a look at campaign filings for Governor Herbert's own campaign show more than $250,000 coming in from polluting industries during 2016 alone.
Matheson says that has no impact on the Governor's decision-making when it comes to air quality.
"There's been no governor in the history of this state that's done more for air quality than Governor Herbert," Matheson said.
Matt Pacenza agrees, for the most part, that Governor Herbert is sincere in his commitment to the issue, but Pacenza says it's crucial for people to make their voices heard so big money isn't the only voice in the room.
"Having the people on your side, or constituents on your side, is no small thing," Pacenza said.
Both Pacenza and Matheson point to the same development on the horizon as giving the most hope for progress on clean air: the next EPA step to tier III gas.
"We think that the combination of cleaner cars and cleaner fuels over the next few years can decrease automobile emissions maybe as much as 80 percent," Matheson said.
But there are two threats to that progress: cutbacks to the EPA and federal regulations in general, and the commitment of Utah's four biggest fuel suppliers to clean fuel.
The Clean Air regulations are so far along and are codified in federal law with the Clean Air Act, so they are likely to continue.
But two of Utah's big refiners have not yet committed to producing tier III gas in Utah, despite Utah's clear need for it.
"Really we'd like to see Holly Frontier and Chevron step up to the plate, follow the lead of Tesoro and Sinclair and produce the Tier three fuels here," Matheson said.