Over three years, the Salt Lake Valley reduced the amount of fine particulate matter in its air, the Environmental Protection Agency has determined, and it will allow Utah regulators to move to a new stage in controlling one of the state’s biggest health problems.

That next stage is what could be 20 years of continued monitoring of the Salt Lake City metropolitan area to ensure there’s no increase in PM 2.5 — the dangerous wintertime pollution that can be so thick residents feel it in their throats.

Utah Division of Air Quality Director Bryce Bird said Friday the state would keep in place all the steps it has taken to improve air quality and is free to take more steps.

“We aren’t proposing any backsliding,” Bird said.

The EPA announcement, which was placed Friday on the Federal Register, said the Salt Lake City area kept its daily average for fine particulate matter within federal clean-air limits in 2016, 2017 and 2018. Utah achieved that through a plan started in 2014 that touched nearly everyone in the valley.

Smokestacks had to install mitigation devices, public transportation and cleaner cars were encouraged, pollution controls on homes and businesses were put in place and even some aerosol hair sprays were banned.

(Mark Hansen | The Salt Lake Tribune) Fireworks at the Fourth of July event at The Gateway in Salt Lake City on July 4, 2019.

But Utah also was able to petition the EPA not to count certain days when it said the air conditions were beyond the state’s control. That included at least one July 4 with fireworks pollution as well as two days when wildfire smoke billowed, Bryce said.

To achieve the EPA’s signoff, the Salt Lake Valley could exceed the federal threshold no more than eight days a year.

Jessica Reimer, a policy associate at HEAL Utah, worries the EPA might have been too lenient in saying Utah couldn’t control the wildfires.

She also contends the valley benefited from three winters when the weather mitigated the bad air better than historical averages. Winter storms typically push out air pollution.

Reimer also worries the EPA designation means the federal government won’t be as vigilant about ensuring Utah is improving its air.

“The state does need to be accountable for those emissions we have in the valley,” Reimer said.

Grace Olscamp, a spokeswoman for HEAL, said the group also worries about the public perception of hearing that Utah has improved its air quality.

“We just don’t want people to think, ‘Everything’s fine now, and I can do a single-occupancy vehicle ride,’” Olscamp said.

Francisco Kjolseth | The Salt Lake Tribune A sizable source of emissions come from tailpipes, and idling and "warming up" your car is a widespread practice in Utah.

Friday’s designation does not apply to ozone — another air pollutant Utah is still trying to tackle.

Air pollution is an issue that has vexed the Wasatch Front for decades and has gotten more complex as the state adds population. Studies have found poor air quality causes asthma and other breathing problems and can even lead to early death in some groups.

A poll over the summer showed air quality was the most pressing issue for voters in Salt Lake City. Both Salt Lake City mayoral candidates have offered plans to improve it.

Bird said the EPA announcement is only one more step on the state’s journey to limit air pollution.

“We know," he said, “that meeting the standard isn’t enough.”