2017 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 2017 Ozone Season (which began March 1 and will end on November 15, 2017):

Table 1:  Four highest ozone readings of 2017 at regulatory monitoring sites (as of March 29, 2017)
Monitoring Site  Highest Reading  ppb  2nd Highest  ppb  3rd Highest  ppb  4th Highest  ppb
San Antonio NW C23 02/23/17   54 03/25/17  51 03/26/17  49   03/15/17  49
Camp Bullis C58 01/31/17  54  02/23/17  53 03/02/17   50 03/26/17  49
Calaveras Lake C59       2/23/17  54   02/22/17  52      01/31/17   51      03/25/17  50
Source:  http://www.tceq.state.tx.us/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 48 ppb, 50 ppb, and 49 ppb, respectively as of March 29, 2017.  When those fourth highest readings are averaged with the fourth highest readings from 2015 and 2016, and demonstrated in Table 2, below, the three year averages are 73 ppb at San Antonio Northwest, 73 ppb at Camp Bullis, and 64 at Calaveras Lake:

Table 2: 2014-2016 3-year average of 4th highest, 8-hour reading at regulatory monitoring sites (as of 3/29/17)            
Monitoring Site     2015     2015     2016  3-Yr Average
San Antonio Northwest C23 79  71 49 66
Camp Bullis C58       80        69        49           66
Calaveras Lake C59       68        62        50           60


Although the 2017 readings are yet to be confirmed by the Texas Commission on Environmental Quality, it is nevertheless apparent that our three-year average is very close to exceeding the standard for ground level ozone at two of the region's regulatory monitors; San Antonio Northwest and Camp Bullis.  At 66 ppb, this three year average is only 5 ppb away from exceeding the standard threshold of 70 ppb--while the ozone season has only begun, and the months during which ozone tends to be the worst are still ahead of us.

Previous to this year, every year since 2012 the San Antonio area has been out of compliance with the federal ozone standards, even though, until last year, the standard threshold had been set at a more lenient 75 ppb compared with the current 70 ppb threshold. 

In October 2017, the EPA expects to designate areas of nonattainment and place them into six possible categories, according to the level of the areas' standard violation, from marginal to severe.  Each of these categories will have progressively stricter regulations designed to reduce pollution and bring them back into compliance with the federal standards. 

Because the San Antonio area has been in noncompliance for the evaluative years of 2014 through 2016 and will likely also be in noncompliance for the years 2015-2017, it is almost certain that it will be required to meet some regulations.  If the area is designated nonattainment at the marginal level, for example, new or expanding manufacturers may be required to secure pollution reductions to offset their proposed growth, and transportation planners may be required to demonstrate that adding capacity to the roadway system would not increase pollution from cars and trucks in order to qualify for federal highway funds for roadway improvements.

Through its efforts to keep pollution at a minimum throughout the rest of the ozone season, however, the San Antonio area may be able to avoid the more stringent restrictions associated with a designation of nonattainment at the moderate level, which would bring additional, more stringent requirements, such as mandatory vehicle emissions testing.