Lowering San Antonio’s ozone levels might require sleuthing out specific sources of pollution instead of imposing widespread measures across the city, a scientist who helped improve Houston’s air quality told City Council members.

Harvey Jeffries, who served as science adviser to a Houston air-quality group, spoke about air pollution in San Antonio at a City Council meeting Wednesday. The City’s Metropolitan Health District has hired Jeffries to study where Bexar County’s ozone pollution comes from and how to reduce it.

If true, Jeffries’ conclusions could mean that current efforts to deal with the ozone issue, such as banning idling by trucks and closing a coal plant, might not be as effective as some had hoped.

Jeffries’ first report came three months after the U.S. Environmental Protection Agency announced that Bexar County’s air quality no longer meets federal standards for ozone, a key component of smog that’s been tied to asthma, other chronic lung conditions, and premature deaths.

Harvey Jeffries, a professor at the University of North Carolina at Chapel Hill, has studied Houston’s air quality. Credit: Brendan Gibbons / San Antonio Report

A professor for 44 years at the University of North Carolina at Chapel Hill, Jeffries has studied air quality issues extensively, especially in Houston. In the early 2000s, scientists in Houston found that occasional belches of air pollution from chemical plants, tanks, and barges made a big difference in ozone levels.

“I’ve always had an interest in other parts of Texas after spending lots of time in Houston,” Jeffries said at the meeting. “It’s interesting to find out that many of the underlying scientific issues that we’ve examined in Houston apply to many other parts of Texas.”

The City paid Jeffries’ company, Othree Chemistry Research and Service, $45,000 for the first phase of his study and recently approved another $45,000 for a second phase.

Where does ozone originate? 

Ozone forms when nitrogen oxide emissions interact with volatile organic compounds in the presence of heat and sunlight. Nitrogen oxides most often come from vehicle exhausts, power plants, industrial sites, cement plants, and other combustion-related sources. Volatile organic compounds are tied to chemical use, chemical storage tanks, and gas stations, to name a few sources.

Instead of using computer models to study where San Antonio’s ozone comes from, Jeffries used measurements of pollution levels and weather patterns taken every hour in the years 2012, 2015, and 2016. He did this for 17 air-monitoring sites around the city.

“I actually look at the observations hour by hour, detail by detail – everything,” he said.

San Antonio has 21 air-monitoring sites, but only three that measure ozone levels for regulatory purposes: one at Calaveras Lake on the Southeast Side, one near John Marshall High School on the Northwest Side, and one just inside the southern fence of Camp Bullis on the far North Side.

Wind patterns make a huge difference in what these monitors record, Jeffries found. Almost every high-ozone day in San Antonio was characterized by winds that shifted in direction in a full or three-quarters circle throughout the day.

At the Camp Bullis air monitor, at least half of the days in the year feature those circular wind patterns. But in 2012, for example, only 18 of those days were high-ozone days.

That means you need both the right wind conditions and the right chemistry for high-ozone days, Jeffries said.

Overall, Jeffries found that on days when the Marshall High and Camp Bullis monitors pick up high ozone, morning winds are often coming from the north-northwest, the opposite direction of the city’s core.

Because of a lack of data, Jeffries could only speculate on the exact source of certain ozone-forming chemicals, but his suggestions for possibilities included storage tanks, road construction, and a wastewater treatment plant at Camp Bullis.

“I don’t understand what the heck is up there,” Jeffries said. “It’s weird, whatever it is, but it certainly comes from that quadrant up there.”

Councilmen Clayton Perry (D10), a retired Air Force lieutenant colonel, and Manny Pelaez (D8) exchanged glances when Jeffries brought up the Army training base.

Councilwoman Ana Sandoval (D7)
Councilwoman Ana Sandoval (D7) Credit: Scott Ball / San Antonio Report

“We don’t go and dictate terms to Camp Bullis, ever,” Pelaez said. “They’re our lifeblood here in town. … In fact, what we try to do is make sure that their missions are as easy to accomplish as possible. I want to make sure that’s not on the list – go and push them around.”

“No,” Metro Health Director Colleen Bridger replied.

Councilwoman Ana Sandoval (D7), who once worked for an air-quality agency in California’s San Francisco Bay Area, called Jeffries’ conclusions “potentially good news.”

“What it means to us as policymakers is we don’t have to implement some citywide or even countywide measure right now to find a reduction in ozone,” she said. “We can use a scalpel and look at that area where the wind is coming from.”

Different studies, different conclusions

Much of the discussion revolved around how different Jeffries’ conclusions are from those reached by the Alamo Area Council of Governments (AACOG).

In the past, local officials have heard how AACOG’s computer modeling of ozone suggests that nearly 80 percent of the ozone in San Antonio’s air in 2017 came from outside the San Antonio metro area, as AACOG Executive Director Diane Rath testified before a U.S. House committee in June.

Texas Gov. Greg Abbott’s staff cited AACOG studies frequently in letters to the EPA, arguing San Antonio should not face additional regulations in part because of air pollution wafting in from elsewhere, including “foreign sources.”

But Jeffries said Wednesday that ozone being formed in the morning near Camp Bullis is coming from only about 12 to 18 miles away.

“So you’re not looking at Mexico – it’s the wrong direction,” he continued. “You’re not even looking at some of the other states – wrong direction. You’re not looking at Austin. You’re not looking at Houston.”

“You’re looking at something over there,” he continued, pointing to the north.

Rath called Jeffries report “interesting” but said she questioned the validity of certain sections that compared San Antonio to Houston.

“We are so different from Houston,” Rath said. “We don’t have the petrochemical industry, we don’t have refineries, and our topography is very, very different. … I’d just like more insight into his conclusions.”

Jeffries said the two cities have similar circular wind patterns, but said the pollution in their air does have little in common.

Current policies might not help

The chemistry of ozone formation is extremely complicated. It’s often difficult for policymakers to figure out whether to try to reduce nitrogen oxides or volatile organic compounds and, if so, by how much, Jeffries said.

“There’s a case if you’re a policymaker, you’re gonna go out and spend a billion dollars and reduce [nitrogen oxides], and the ozone problem’s going to get worse,” he said. “That makes this very difficult to deal with.”

The future of autonomous vehicles could mean big changes to how we transport large quantities of goods.
Local ordinances to improve air quality include a ban on heavy truck idling. Credit: Flickr CC / Paul Sableman

So far, state and local officials have focused mostly on reducing nitrogen oxides. This includes local ordinances banning heavy truck idling, CPS Energy’s planned closure of its Deely coal-fired generators, and the pursuit of $73 million in Volkswagen settlement funds to convert vehicles from diesel to more efficient fuels.

Regardless of their effect on ozone, those strategies remove other types of air pollution and cut down on greenhouse gas emissions that drive climate change, Bridger said.

Jeffries said data on volatile organic compounds is scarce for San Antonio. He suggested using an infrared camera to survey for plumes of pollution in the area, as has been done in Houston.

“We’re not talking about large quantities,” he said. “It could be one guy up there with some particular thing. … You could have a tank that’s sat there forever and nothing shows up, and one day a hole appears in it, and all kinds of [pollution] show up.”

The City has issued a request for information for potential consultants to propose how they might address volatile organic compounds, Bridger said.

Brendan Gibbons

Brendan Gibbons is the San Antonio Report's environment and energy reporter.