Exceptional Events

Principal Investigator: John Lin, University of Utah

Wildfires and dust storms are considered “exceptional events” in air quality modeling because they are not reasonably controllable or preventable, are caused by human activity that is unlikely to recur at a particular location, or are a natural event. Exceptional events can unpredictably increase concentrations of pollutants like particulate matter (PM) and ozone precursors, especially downwind of the events. Until now, it has been difficult to quantify the effects of these events on Utah’s air quality and to separate their effect from the effect of other sources of pollution. Separating out these effects, known as source apportionment, is critical to demonstrating which sources can be controlled by regulatory measures and which are beyond regulatory control.

Relevant Documentation