SALT LAKE CITY — Each of the charts in this story takes the same daily figure called the Air Quality Index (AQI) for PM2.5 particulates.
The AQI is a standardized daily figure reflecting the concentration of a pollutant.
The EPA and other regulators determine the AQI for several pollutants. The two most significant for Utah are PM2.5 particulates and ozone.
PM2.5 is most commonly associated with trapped emissions during winter temperature inversions, while ozone spikes are created as a chemical reaction requiring sunlight and heat and thus commonly occur on the hottest summer days.
These charts are only using data on PM2.5 because that’s what we are experiencing from wildfires. Ozone pollution is separate and still a problem during the summer months.
Every chart uses data from the same air quality monitoring station operated by the Utah Department of Environmental Quality. The station at Rose Park (490353010) has data available from mid-2007 to the present. For these charts, we used the data from the first full calendar year to the last day’s data available as of this report, which is Aug. 29, 2021.
Here's the overall average daily AQI for the entire data set we used. Below it, you’ll see how much the cycle of particulate pollution is changing.
This chart is the average from 2008-2014 (approximately half of the station’s available data). It shows what Wasatch Front, Cache Valley and Uintah Basin residents have come to see as the cycle of particulate pollution, dominated by the winter inversion season.
2015 to the present shows the cycle changing to form a significant second annual peak of particulates in the summer.
The average monthly AQI for this year shows how bad August has been and also an improvement in winter particulate pollution.