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Missoula’s airshed got a mixed blessing Tuesday, earning a long-sought pollution-free status just as it was getting socked in from wildfire smoke.

And the afternoon winds that cleared much of that smoke away were likely to aggravate the growth of forest fires that may compromise air quality for much of August.

The designation "referred to pollution sources we have some sort of control over,” Missoula City-County Air Quality specialist Sarah Coefield said of the federal label the community has tried to shake for decades. “Fortunately, we can’t go into non-attainment" – the formal name for the designation – "over wildfire smoke.”

On Tuesday, the Montana Department of Environmental Quality formally asked the U.S. Environmental Protection Agency to declare Missoula in compliance with national air quality standards. Missoula has been considered a “moderate nonattainment area” since 1990 because of the amount of particulate matter 10 micrometers or smaller in the air. That material, known as PM-10, typically came from wood smoke and road dust trapped in the airshed by Missoula’s surrounding mountains.

Over the past two decades, city and county officials passed rules prohibiting installation of wood-burning stoves and heaters in the valley, reduced the amount and kinds of traction sand applied to icy roads and stepped up cleaning efforts to remove sand after the ice had melted. Those sources made up about 92 percent of the PM-10 pollution. Monitoring data showed Missoula hasn’t violated the federal PM-10 standard since 1989 for either average or peak levels.

The federal nonattainment designation was important because it forced businesses like Roseburg Forest Products to use stricter standards in its facility improvements than similar factories in places with less air pollution. Under the new designation, companies like Roseburg will have to show that their changes won’t cause new ambient air quality violations, according to DEQ public policy director Kristi Ponozzo.

“Montanans value clean air and water, and the community of Missoula has led the way to move the City into compliance with air quality standards,” noted DEQ Director Tom Livers. “Once Missoula is re-designated, business and industry will have increased opportunities to grow, expand, and create good-paying jobs.”

That doesn’t help the immediate air quality, which was rated “unhealthy” in Hamilton on Tuesday afternoon because of smoke from the Roaring Lion wildfire just southwest of town. Missoula’s air quality was nearing that level before forecast late-afternoon winds began reaching the valley. It was rated “good” late Monday afternoon.

“I was looking at maps from all the weather stations in the region, and those strong winds are everywhere but Missoula and the Bitterroot,” Coefield said on Monday afternoon. “The winds will scour the valley clean, but with the caveat of what that means for fire activity. If the fire blows up more, we’ll see more smoke. Wildfire smoke is an issue every summer, and it’s more of a concern than it was 15 or 20 years ago. It’s become the primary source of pollution in Missoula for the time being.”

And just to complicate matters for Missoula, it’s not Roaring Lion smoke that’s filling the local air. Most of that pollution is blowing toward Butte. Instead, another blaze called the Cedar Fire 11 miles south of the Powell Ranger Station in Idaho has a wind channel for shooting smoke into the Missoula Valley. That fire has burned 1,371 acres in the Selway-Bitterroot Wilderness and is not being actively confronted.

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Natural Resources & Environment Reporter

Natural Resources Reporter for The Missoulian.