Ozone Levels in 2015: Did Wildfires Play A Role?

The greater Houston region has been working for many years to meet EPA’s health-based standard for ozone.  Over the past 15 years, we have seen significant decreases in both ozone levels and the number of days that the standard was exceeded in Houston.  In fact, 2014 was our cleanest year on record.  In 2015, however, we saw increased ozone in the region.  The levels of ozone were slightly higher, and the number of days we exceeded the standard was higher as well.  Scientists are still working to understand the reason for the higher ozone.  We know that weather is a key factor that drives ozone formation.  Some years have more days with hot, dry, stagnant weather that can contribute to more days with high ozone.

Another factor that that scientists will investigate is whether there were more or fewer agricultural and wildfires in 2015 than in an average year.

Another factor that that scientists will investigate is whether there were more or fewer agricultural and wildfires in 2015 than in an average year. Smoke from wildfires can cause higher ozone levels.  Sometimes that smoke can travel hundreds of miles, as it does each spring when farmers in Central America and Mexico burn off their fields in preparation for planting.  (Central America Smoke Season). According to the National Interagency Fire Center, more land in the U.S. had burned between January 1 and September 15 of 2015 than in the same period in any year in the past decade

According to the National Interagency Fire Center, more land in the U.S. had burned between January 1 and September 15 of 2015 than in the same period in any year in the past decade.

In August of 2015 there were numerous and widespread wildfires both nearby and far away from Houston.  The image below was created by the U.S. National Oceanic and Atmospheric Administration (NOAA).  Each small fire icon represents a fire that was burning on August 28, 2015.  The red shaded regions are areas covered in heavy smoke, yellow and green areas are covered in medium and light smoke.  The two yellow lines show the directions that winds took in the days leading up to the 28th.  As you can see, winds passed through numerous wildfires and smoke-filled regions both near and far.

NOAA_Smoke_Levels

Source:  NOAA Office of Satellite and Product Operations

August 28th, 2015, was one of the most severe and widespread ozone days recorded in Texas in 2015.

August 28th, 2015, was one of the most severe and widespread ozone days recorded in Texas in 2015. Monitors around much of the state measured ozone exceedances on the days leading up to and including the 28th.

The Clean Air Act is the federal law that establishes the framework for what states must do to maintain and improve air quality where needed.  It recognizes that wildfires and other natural processes like dust storms can have an impact on local air quality that states cannot control.  It allows states to “flag” days when they can demonstrate that there would not have been an exceedance without the influence of exceptional events like wildfires.  If EPA agrees with the state’s demonstration, that flagged day will not be used to determine whether an area meets federal health based standards.  As EPA’s standards have continued to be set at ever-lower levels, the importance of wildfires as a background contributor to local ozone continues to grow.

For More Information On Wildfire Impacts on Air Quality: https://www.airnow.gov/index.cfm?action=smoke.index

To See Real Time Fires and Smoke Images:  http://www.ospo.noaa.gov/Products/land/hms.html

Wildfire Data in Recent Years:  http://www.nifc.gov/fireInfo/nfn.htm