2016 Ozone Season

What is an "Ozone Season"?

An ozone season is a period of time in which ground-level ozone, which is the most common type of air pollution we have in the Alamo Region, typically reaches its highest concentrations in the air we breathe. In this region, the ozone season stretches from April through October. Ground-level ozone reaches its highest concentrations during these months because ozone forms when nitrogen oxides mix with volatile organic compounds in intense sunlight, and sunlight is strongest from April through October. It is during this time that we are most likely to have exceedances of the National Ambient Air Quality Standard for ground-level ozone.

Air Quality Exceedances and Ozone Action Day Alerts
According to the new National Ambient Air Quality Standard (NAAQS) set by the U.S. Environmental Protection Agency (EPA) in 2015, ozone levels are considered to be unhealthful when they rise above 70 parts per billion (ppb). The standard is based readings taken at regulatory monitors during eight-hour blocks of time. EPA uses the average of the annual fourth highest eight-hour daily maximum concentrations from three years of air quality monitoring data to determine whether the ozone standard has been violated.

High concentrations of ozone can cause shortness of breath, coughing, wheezing, headaches, nausea, eye and throat irritation, and lung damage. People who suffer from lung diseases like bronchitis, pneumonia, emphysema, asthma, and colds have even more trouble breathing when the air is polluted. These effects can be worse in anyone who spends significant periods of time exercising or working outdoors.

When it is anticipated by scientists at the Texas Commission on Environmental Quality (TCEQ) that an exceedance of 70 ppb during an 8-hour period will occur the next day, the TCEQ issues an Ozone Action Day, so that health precautions and preventative measures may be taken.Health precautions may include limiting outdoor activity, while preventative measures may include driving less or avoiding traffic congestion, since the formation of ozone in this region is linked in great part to vehicle exhaust.

2016 Exceedances and Alerts

There were two Ozone Action Day Alert issued by the TCEQ during the 2016 Ozone Season, as shown in the table below. There were also five days on which there was an actual exceedance during an 8-hour period at one or more of the San Antonio areas three regulatory monitors, which are located at Marshall High School (San Antonio Northwest), Camp Bullis, and Calaveras Lake. 
 Date Alert Level*  Highest 8-hour reading at a Regulatory Site  
  04/23/16   Orange  69 - San Antonio NW (Orange level was not reached)
 05/05/16  No Alert Issued  73 - San Antonio NW
 05/06/16  Orange  71 - San Antonio NW
 09/28/16  No Alert Issued  71 - Calaveras Lake
 10/02/16  No Alert Issued  76 - San Antonio NW
 74 - Camp Bullis
 10/11/16  No Alert Issued  81 - Camp Bullis
 72 - San Antonio NW
For more information specific to the 2016 Ozone Season, please click here.

* Air Quality Health Alerts are issued when it is predicted that the region's ozone will reach the orange level or higher on the Air Quality Index. At the orange level, our air is unhealthy for sensitive groups, including children, people who are active for prolonged periods outdoors, and those with respiratory illnesses. Fortunately, since 2002, the regulatory monitors in the Alamo region have not recorded an exceedance at the next highest level, red, which would be considered unhealthy for everyone.