Dirty air recap with a look at mandatory action days

Local News
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SALT LAKE CITY, Utah (ABC4 News) – Dirty air. Nobody wants to breathe it, right? With our active storm pattern this winter season, it seems like prolonged periods of inversion weren’t quite as bad, but the numbers tell a different story in Northern Utah Counties.

The Department of Environmental Quality, the parent branch over Utah’s Division of Air Quality, tracks pollution and issues voluntary action and mandatory action days when pollution exceeds the state standard. The standard was amended in the fall of 2012 and currently sits as the PM 2.5 forecast. Pollutants have to be at or over 25 micro grams per cubic meter in order to see a mandatory action day.

Voluntary action days are issued as a way to alert the public pollution is building, and mandatory action days don’t allow open burning or the usage of coal or wood burning stoves or fireplaces. Those actions contribute to pollution which gets trapped under a temperature inversion. Inversions are tricky. A thick layer of cold air gets trapped under a layer of warm air. In the atmosphere, the temperature typically decreases with height, but under an inversion, the opposite happens. Cold air is trapped on the valley floor, and warming happens along the benches and in the mountains. Our mountains surrounding populated valleys contribute to inversion by preventing the movement of air, which is why we need decent sized storms to mix the air. Winter sunshine, which is low in the sky, supplies less warmth to the Earth’s surface so the cold air often stays trapped until a storm moves through. 

This year, the state of Utah has seen an active storm pattern. Snow, wind, and rain, we’ve seen it all and one would assume that means less inversion, but that’s not exactly the case. Mandatory action days were higher this year compared to last year in Salt Lake County, Utah County, Weber County, Cache County, and Box Elder County. 

Voluntary action days are used to alert the public to rising pollution levels, and several counties saw an abundance of voluntary days including the eastern side of the state.

The population also adds to pollution, which is one of the reasons our heavily populated areas like Salt Lake, Utah and Cache County see more mandatory action days. Watch Meteorologist Alana Brophy break down the numbers on Facebook Live below.

While winter inversion season is wrapping up, we have to monitor air conditions during wildfire season because smoke increases pollution and during the summer months due to ozone. To track air quality, DEQ has an app you can download here for Android users: 

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