Utah’s Air: Double-Punch of Ozone and Wildfires this Summer

By Donna Kemp Spangler

Originally Published Summer 2018

Wildfires burning throughout the West have many people questioning whether this is the worst summer ever for air pollution. It’s not, but it has been worse than many other years, thanks to the double-punch of high ozone levels and wildfire smoke.

Summer heat is certainly a recipe for ozone, and the various air monitors across the valley registered high ozone levels on many days. Wildfire smoke also sends soot in the form of tiny particulate pollution wafting into the valley.

There’s no question that the wildfires have had an impact on Utah air. But the impact depends on where the fires are burning and the direction the wind is blowing. If wildland fires continue to be the norm, then the impact on air quality in Utah will vary from year to year depending on meteorological conditions.

The Utah Department of Environmental Quality’s Division of Air Quality (DAQ) monitors and records the federal ozone standard, set at 70 parts per billion (ppb) over an eight-hour period. But the ozone is only part of the overall impact during the summer. DAQ also monitors for particulate pollution of various sizes. The smaller the particle, the bigger the health risk because those microscopic particles get lodged in the lungs while breathing.

Wildfires are mostly to blame for high levels of the particulate pollution (PM _2.5) we see during winter inversions. Fires burning in Utah have a direct impact on the local community air quality. This primary particulate matter is emitted directly from construction sites, wildfires, wood burning, gravel pits, agricultural activities, and dusty roads. Fires in California, Oregon, Idaho and elsewhere can have regional impacts. Montana got hit particularly hard last year from wildfires burning in those states.

I asked Kristy Weber, meteorologist for the Division of Air Quality, to do some research, and she found Utah County exceeded the federal standard of 35 micrograms per cubic meter of air (ug/m3) during the month of July and August due to smoke from the Dollar Ridge Fire and others. Salt Lake Valley didn’t necessarily exceed the standard, but as you can see from the second chart, there were spikes associated with fires and fireworks that appear more dramatic compared to the 10-year average.

A couple of other observations Kristy noted:

• July 4^th fell on a Wednesday. There were bigger peaks noted on Thursday and Friday evenings, probably because more people were lighting off fireworks.
• At the end of July, a period of easterly winds caused the Wasatch Front to be engulfed in smoke from the Dollar Ridge Fire near Strawberry Reservoir.
• At the end of July and beginning of August, high particulate pollution was measured initially in southern Utah County, with spikes seen in the late night/early morning hours. This was a result of smoke from the Coal Hollow Fire from Spanish Fork Canyon/U.S. 6. This smoke eventually made its way to Salt Lake County and other parts of the Wasatch Front and Northeast Utah in the following days.
• Towards the end of August, we had a series of disturbances along the Wasatch Front. Southwest winds would often precede the frontal passage, resulting in lower particulate-matter numbers, especially as showers and thunderstorms engulfed the area. Post-frontal passage would be accompanied by smoke-laden but cooler northwesterly winds. This happened a number of times, which is why there were such strong spikes/falls at the end of the month.
• Of note, even though there were times during the day when monitored values were above EPA’s standard for PM_2.5 in August, this is not reflected in the plots since the standard is based on a 24-hour average at a monitor for each day.

Summer is almost over, and the ozone and wildfire seasons are winding down. Our air quality took a bit of a beating this year, but we can hope for better conditions next summer and do our part to reduce our emissions and prevent wildfires.

There are times when the air looks smoggy due to diffused light; it doesn’t mean the air quality is unhealthy. That’s why it is important to follow the air-quality conditions on DEQ’s web page air.utah.gov. and on your smartphone by downloading the UtahAir app. We can’t control the weather, but we can control our actions and make smart choices for good air quality. Visit Utah Clean Air Partnership (UCAIR)  for tips on how you can help improve our air.

I am the Communications Director for DEQ and a former reporter for the Deseret News. I am a frequent blog contributor.

Contact our PIO at deqinfo@utah.gov with further questions.