As a deadline to clean Bexar County’s air approaches, a recent study by Texas regulators indicates locals could breathe easier if not for pollution wafting in from outside the U.S. 

The Texas Commission on Environmental Quality modeled emissions in the San Antonio area in response to the U.S. Environmental Protection Agency’s 2017 declaration that Bexar County air is too polluted to meet federal health standards. The TCEQ’s findings represent some of the latest available data on the sources of San Antonio’s ozone, the only pollutant with concentrations considered too high in the city’s air.

If not for emissions from northern Mexico, southern Canada, and other countries, San Antonio’s air likely would be clean enough to meet the EPA’s 2015 standard of 70 parts per billion (ppb) for ozone, the TCEQ study states. In 2017, the EPA found that Bexar County’s air violated that standard at 74 ppb. 

The study is relevant because of an upcoming deadline that will decide whether San Antonio will be under more stringent federal scrutiny for its air quality. Failing to attain the 70 ppb standard by December 2020 could trigger more stringent regulations that raise air quality permit costs for businesses and could delay planning for new transportation projects.

The TCEQ estimates that 2 to 3 ppb of San Antonio’s long-term ozone averages are a result of pollution blowing in from outside the country, the study states.  

The findings indicate that while foreign emissions might tip the scales, a majority of the ozone-forming pollution that fouls local air comes from local sources. That means local efforts to do something about it can make a difference for public health, Mario Martinez, assistant director of San Antonio’s Metropolitan Health District said.

That’s why Metro Health remains focused on its efforts to improve air quality and connect residents to resources that can help better manage air quality-related issues like asthma, Martinez said. 

Bexar County has the highest rates of children going to the hospital for asthma in Texas, according to State statistics. Health care providers say that’s due only in part to poor air quality, with factors like allergies and high poverty rates also playing major roles.

People with asthma and other sensitive groups face a higher risk of attacks during high-ozone conditions. That’s because ozone – three oxygen atoms bound together – can irritate and damage the lungs and has been linked to chronic lung conditions. Ozone levels are tied to power plants, manufacturing sites, and outdoor chemical use, among other emissions sources. 

Over the past 20 years, San Antonio has seen its air quality improve, even as the city has grown. The city now on average sees fewer ozone spikes per year than during the early 2000s, according to the TCEQ study. 

However, the EPA also has tightened its standards in response to new science about how ozone affects public health. In 2015, the Obama Administration’s EPA lowered the standards from 75 ppb to 70 ppb. 

Texas officials have for years focused on data tying San Antonio’s ozone to foreign countries. In letters to the EPA, Texas Gov. Greg Abbott’s office blamed cross-border pollution, as did Alamo Area Council of Governments (AACOG) director Diane Rath in a 2018 U.S. House committee hearing. 

However, the recent TCEQ analysis offers fresh science to back up the claim. The agency used multiple computer models to separate likely international pollution from emissions tied to Texas industrial sites and tailpipes.

For San Antonio, whose ozone averages tend to hover slightly above the 70 ppb deemed acceptable, 2 to 3 ppb could make a big difference in the stringency of the EPA regulations that could apply during the coming years. 

Martinez said San Antonio could still come in under the 70 ppb limit by the 2021 deadline, depending on how many ozone spikes the city experiences in 2020. In San Antonio, ozone season runs from March to November. 

“It is possible if we’re following the strategies that were outlined” in Metro Health’s ozone attainment plan, Martinez said. “The combination of the weather, the meteorology, the chemistry – we just don’t know what the summer’s going to look like.”

Among other initiatives, Metro Health has contracted with researchers at Southwest Research Institute (SwRI) to hunt for mystery pollution sources near the TCEQ’s air monitoring sites in northern Bexar County, Martinez said. 

The tools they use to find them include infrared cameras that can identify plumes of emissions invisible to the naked eye. SwRI’s fieldwork is ongoing, and Metro Health expects to have results by late summer, Martinez said. 

The TCEQ is holding a public comment on its study until Feb. 19. The agency will hold a public hearing at 2 p.m. on Feb. 18 at AACOG’s offices at 8700 Tesoro Dr. 

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Brendan Gibbons

Brendan Gibbons is a former senior reporter at the San Antonio Report. He is an environmental journalist for Oil & Gas Watch.