Scott G Winterton, Deseret News
Bad air in the Salt Lake Valley Monday, Dec. 30, 2013.

SALT LAKE CITY — The inversion season last year was one of the worst in about a decade, and the Wasatch Front is off to a bad start again this winter.

Though the air in northern Utah seems bad now, it’s actually better than it was 20 or 30 years ago, state officials say.

Already this season, Salt Lake and Davis counties have seen 16 mandatory action days and 14 voluntary action days. Last year, there were 35 mandatory action days.

"Last January was one of the worst we'd seen in years, perhaps a decade,” said Bo Call, air monitoring manager for the Utah Department of Environmental Quality.

Early snow, cold temperatures and few storms are just what the state saw early this season.

"That led us into it much earlier,” Call said.

A cold front is expected to push through Friday night and help mix up the nasty air that’s been stuck over most of northern Utah, improving the air quality for Saturday, but the inversion will build back up again next week, KSL meteorologist Dan Guthrie said.

In addition, the Environmental Protection Agency tightened its standard seven years ago.

"The year that the standard changed, 2006, the number jumped up, because all of a sudden we are over that standard,” Call said.

Plus, the department got more proactive about warning Utahns as the pollution builds, resulting in alerts more often. What used to be a yellow, moderate day is now often a red, unhealthy day.

"It's a much more preventative measure than it has been in the past,” Call said.

Still, the air people breathe now is much cleaner than it was a few decades ago, air quality officials said. One reason is that today’s cars and industry pollute less.

"We've been monitoring the air pollution since the '70s, and we can see a steady decline across the board in every aspect of air pollution, so it is getting better," Call said.

Public education has also made a big difference, he said.

“Instead of getting most of my calls about whether people can burn, I’m getting calls about what they can do to reduce pollution or whether they can go outside, whether it’s a good day for them to exercise,” Call said.

But greater awareness has also lowered Utahns' tolerance for the pollution, he said.

"Are we more aware of it? Are we willing to accept less? Yes. That's the way it is," Call said.

Collectively, Utahns drive 30 million miles on an average day on the Wasatch Front, and cars make up 55 percent of the pollution. The biggest difference anyone can make is to drive less, air quality officials said.