Think The Air Has Been Particularly Bad This Summer? Well, It’s Been Worse Before

August 28, 2019
Hazy DenverHazy DenverKevin J. Beaty/Denverite
Denver's air quality is visibly not great on Aug. 20, 2018.

Have you been thinking there have been more ozone advisories on the front range this summer? CPR listener Mark Bourne thought so.

"How many times this year has Denver been under a health advisory due to air quality concerns and is it more than normal, less or the same? It feels like a lot more than normal."

It turns out the opposite is true.

Wednesday marks the 30th Ozone Action Alert Day for Colorado's Front Range.

That is relatively low compared to the last three years, according to Scott Landes, an Air Quality Meteorologist with the Colorado Department of Public Health and Environment. Between May 31 and August 31 last year there were nearly double the number of Ozone alert days as there have been this year.

The numbers of ozone alert days between May 31 and August 31 of the last three years are as follows:

  • 2016: 36
  • 2017: 45
  • 2018: 52

The highest concentrations of ozone Wednesday are likely in the southern and western portions of the Denver Metro area, as well as the northern foothills in Boulder, Longmont, and western Fort Collins.

CDPHE issues an alert when concentrations of ozone are expected to be in the moderate to "Unhealthy for Sensitive Groups" range. That threshold is an 8-hour average of more than 70 parts per billion.

The EPA says ozone forms near ground level when ultraviolet radiation interacts with volatile organic compounds (VOC) and nitrogen oxides (NOx). High ozone levels can also form in colder winter months.

On alert days, health officials recommend active children and adults and people with lung diseases reduce heavy or prolonged outdoor exertion. The air could also be unhealthy for the elderly to breathe.

The state also puts the alert on freeway signs directing people to cut down on their driving and to avoid refueling their vehicles during the alert period.

"I commute to work on my bike so I'm always checking to see what the weather is going to be," Bourne said. "It just seems like every day there's an alert on ozone or air quality saying, 'Don't do strenuous activities outside.' It's hard to stop driving and commute on a bike when you're getting those types of advisories."

"Ozone season" is winding down in Colorado, Landes said. Ozone is most likely to reach unhealthy levels on hot sunny days in urban environments, according to the Environmental Protection Agency.

Wondering what the air quality is like where you are? You can view that here.