Traffic lines up on Interstate 35 heading south.
Traffic builds up on Interstate 35 heading south. Credit: Bonnie Arbittier / San Antonio Report

San Antonio is among the top 10 cities in the U.S. for childhood asthma cases specifically related to air pollution from cars and trucks, according to a modeling study.

Estimates based on air pollution and public health data indicate that San Antonio was No. 10 out of cities in the U.S. in 2010, with 592 cases of childhood asthma attributable to exhaust from vehicle tailpipes, according to research by the Center for Advancing Research in Transportation Emissions, Energy, and Health. Texas A&M University’s Transportation Institute leads the research consortium.

The research also involved looking at the change between estimated traffic-related child asthma cases in 2000 and 2010. The number of cases nationwide decreased by about a third in that interval.

Haneen Khreis, an assistant research scientist at Texas A&M, said that could be the result of better vehicle standards, increased regulations, and lower overall vehicle miles traveled as a result of the Great Recession.

“My personal feeling is that regulation is a big part of it,” Khreis said.

As part of the study, the researchers created a map of the entire U.S. by county and ranked cities by the number of child asthma cases attributable to traffic. The top 10 cities loosely correspond to population, with San Antonio falling behind Houston and Dallas. Those two cities had 1,240 modeled cases and 779 cases, respectively.

“We know how many [asthma] cases are happening in each county,” Khreis said. “The big question is what is the percentage of these cases that you can attribute back to air pollution?”

As with all major cities in the U.S., data on San Antonio’s air pollution and its rates of childhood asthma are easy to access, though it’s rare to have researchers rigorously parse the relationship between the two. Other major sources of air pollution in San Antonio also include large stationary sources like power plants, cement kilns, and manufacturing sites.

“It’s nothing new that I hadn’t heard before,” said Adelita Cantu, an associate professor of nursing at UT Health San Antonio, after looking at the study. “We have a very significant issue with asthma here in San Antonio.”

San Antonio has a relatively high rate of child hospitalizations for asthma compared to other parts of Texas. Physicians and public health experts say that’s due to several factors, including air quality, pollen and other allergens, and poverty that makes managing asthma symptoms difficult.

Cantu often looks at public health on a large scales, focusing on the structural issues that determine people’s health. That includes the quality of the air people breathe.

“You can’t separate health from the environment or environment from health,” Cantu said.

Khreis said that she and her colleagues used a pollutant called nitrogen dioxide as a “marker” of traffic air pollution, which allowed them to narrow down the number of cases where the risk of asthma was increased specifically because of traffic-related air pollution.

“It’s mainly related to traffic,” Khreis said. “It’s not 100 percent traffic. … If there was a way to calculate the specific contribution of traffic to that [nitrogen dioxide] level, that number might become lower, but my guess is that it wouldn’t become much lower.”

Nitrogen dioxide can cause lung problems on its own, but it’s also an ingredient in ozone, which forms when oxides of nitrogen interact with other pollutants in the presence of heat and sunlight. In 2018, federal regulators officially designated Bexar County in “nonattainment” with a federal health standard for ozone meant to protect public health.

Since then, the City’s Metropolitan Health District has developed a plan to lower emissions below the threshold by December 2020. It’s also been working to help families address with the causes and symptoms of childhood asthma.

Cantu has been involved with these initiatives, including SA Kids BREATHE, a program that’s especially focused on helping manage asthma symptoms. It involved a handful of Metro Health community health workers, or promotoras, who visit the homes of children known to be struggling with asthma.

There they can help parents learn to better manage common asthma triggers like cockroaches or pet dander, Cantu explained. They also work with nurses in school districts to help children avoid an asthma attack at school.

For more than two years, Cantu has also organized an Air Quality Academy, which is “geared towards cultivating citizen scientists among our youth, particularly the most vulnerable youth that are disproportionately affected,” she said.

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