2018 Air Quality Status

Ground-level ozone forms when nitrogen oxides (such as those found in vehicle exhaust) combine with volatile organic compounds (such as those found in gasoline fumes) during periods of intense sunlight. Ozone is the most prevalent form of air pollution in the Alamo region.  Attainment of the Environmental Protection Agency's (EPA's) 2015 National Ambient Air Quality Standard (NAAQS)
for ground-level ozone is based on a three-year average of the annual fourth highest, eight-hour reading at any one of the area’s three regulatory monitors, which are located at Calaveras Lake, Camp Bullis, and Marshall High School (referred to as San Antonio NW). In order to be in compliance with the standard, the three year average must be no higher than 70 parts per billion (ppb).

Table 1 below lists the four highest daily maximum eight-hour ozone concentrations measured at the area's three regulatory monitoring sites during the 2018 Ozone Season (which began March 1 and will end on November 30, 2018):

Table 1:  Four highest ozone readings of 2018 at regulatory monitoring sites (as of 09/05/18)
Monitoring Site  Highest  ppb  2nd Highest  ppb  3rd Highest  ppb  4th Highest  ppb
San Antonio NW C23  08/02/18   83 05/07/18  75 07/27/18  73  04/23/18  73
Camp Bullis C58 08/02/18  83      05/07/18  83 04/23/18   77 07/26/18  73
Calaveras Lake C59      08/01/18  79      08/02/18  73      05/07/18   71      05/06/18  71
Source: https://www.tceq.texas.gov/cgi-bin/compliance/monops/8hr_4highest.pl
Table 1 shows that the fourth highest, eight-hour average reading at the three regulatory monitors in the region, San Antonio Northwest, Camp Bullis, and Calaveras Lake, were 73 ppb, 73 ppb, and 71 ppb, respectively as of September 5, 2018.  When those fourth highest readings are averaged with the fourth highest readings from 2016 and 2017, and demonstrated in Table 2, below, the three year averages are 72 ppb at San Antonio Northwest, 71 ppb at Camp Bullis, and 66 at Calaveras Lake:

Table 2: 2016-2018 3-year average of 4th highest, 8-hour reading at regulatory monitoring sites (as of 05/05/18)            
Monitoring Site     2016     2017     2018  3-Yr Average
San Antonio Northwest C23 71  73 72  72
Camp Bullis C58       69        72        73           71
Calaveras Lake C59       62        65        71           66

Source: https://www.tceq.texas.gov/cgi-bin/compliance/monops/8hr_attainment.pl

Although the 2018 readings have yet to be confirmed by the Texas Commission on Environmental Quality, it appears that our three-year average is exceeding the standard for ground level ozone at two of the region's regulatory monitors. The three-year average of the fourth highest, eight-hour reading at San Antonio Northwest is 72 ppb and Camp Bullis is 71 ppb for the years 2016 through 2018. 
Since 2012, regulatory monitor readings have indicated that San Antonio has been out of compliance with the federal ozone standards, even though, before 2015, the standard threshold had been set at a more lenient 75 ppb compared with the current 70 ppb threshold. 

While the other twelve counties that surround San Antonio and make up the Alamo Area were officially determined to be unclassifiable earlier this year, the US Environmental Protection Agency designated Bexar County in non-attainment of its Ozone Standards on July 17, 2018, with an effective date of September 24, 2018.  Of six possible non-attainment categories that have progressively stricter regulations designed to reduce pollution and bring them back into compliance with the federal standards, Bexar County was placed in the least strict (marginal) category, due to the fact that its violations register just slightly over the threshold. 

The designation's requirements, even at a marginal level, will directly impact new or expanding businesses as well as transportation agencies, and will have rippling effects throughout the region's economy.  It is expected, however, that these requirements will help bring healthier air to the area.  Through its ongoing efforts to reduce air pollution, the San Antonio area may also be able to avoid the more stringent restrictions associated with a designation of non-attainment at the moderate level, which would bring additional, more stringent requirements, such as mandatory vehicle emissions testing.