Ending San Antonio’s run as the largest clean-air city in the country, the U.S. Environmental Protection Agency on Wednesday officially designated Bexar County’s air too polluted to meet a federal standard for ozone.

The EPA’s decision means stricter regulation of San Antonio’s air quality. The regulation is meant to within three years return ozone pollution to a level that will safeguard people with chronic lung conditions and prevent more illnesses from developing.

That will likely increase costs on new or expanding industrial businesses and change the way local governments plan transportation projects.

“We look forward to supporting Texas as they work to improve air quality and foster economic opportunity,” acting EPA Administrator Andrew Wheeler said in a prepared statement. “Information provided by the state indicates that the San Antonio area is on the path toward attainment, and we expect Bexar County will be able to demonstrate that it meets the standard well in advance of the attainment date in 2021.”

The EPA has only designated Bexar County as needing additional regulation, with air quality in seven neighboring counties still deemed clean enough to meet the standard. Some local officials have said that would give an economic advantage to San Antonio’s neighbors, whose vehicles and other emission sources add to the pollution in Bexar County’s air.

In a statement Wednesday, Bexar County Judge Nelson Wolff said the agency’s decision would prove extremely costly to residents.

“The EPA ignored a long track record of improving air quality in Bexar County,” Wolff said. “We are extremely disappointed and will examine every possible remedy.”

Bexar County Judge Nelson Wolff. Credit: Bonnie Arbittier / San Antonio Report

Ozone – three oxygen atoms bound together – is a type of pollution that comes from emissions from power plants, industrial sites, vehicle exhaust, and outdoor chemical use. It irritates and damages the lungs and has been linked to chronic conditions like asthma.

The EPA made its decision using air quality monitoring data and its own modeling studies. It released some of its results in a March technical document.

Based on the monitoring numbers, Bexar County’s ozone levels are clearly higher than they are required to be under the air quality standard.

From 2015 to 2017, the period of record for the EPA’s decision, San Antonio’s average ozone levels were calculated at 74 parts per billion. The standard is 70 parts per billion.

This year, San Antonio has experienced six days on which ozone reached levels considered unhealthy for sensitive groups, according to air monitoring data from the Texas Commission on Environmental Quality (TCEQ).

Under the federal Clean Air Act, the TCEQ must now enact a state implementation plan outlining ways to clean up San Antonio’s air.

The likely outcome will be stricter regulations on industrial facilities moving to or expanding in San Antonio. Planning for new transportation projects might take an additional six to 18 months.

The EPA’s decision seems to reflect some imperviousness in the agency’s inner workings to outside political pressure. Since 2017, Republican Texas Gov. Greg Abbott has been trying to persuade the EPA that San Antonio doesn’t need any additional regulation on its air.

Abbott spent years suing the EPA as Texas attorney general, a background he shared with former Oklahoma Attorney General Scott Pruitt, who served as EPA Administrator from February 2017 until his resignation in early July.

In April, the Trump Administration issued a memo directing Pruitt to give more weight to pollution wafting in from foreign countries, among other mitigating factors, when making official air quality decisions.

Most San Antonio political leaders, including Wolff, San Antonio Mayor Ron Nirenberg, and Diane Rath, executive director of the Alamo Area Council of Governments, have argued the EPA shouldn’t impose any additional ozone regulations on San Antonio. In return, they pledged to enact local policies to clean up the air.

Included were 2017 bans by Bexar County and the cities of Leon Valley San Antonio on heavy truck idling. The City, CPS Energy, the San Antonio Water System, and VIA Metropolitan Transit converted more of their fleets to compressed natural gas, hybrid, and electric vehicles.

The closure later this year of CPS Energy’s Deely units – the utility’s oldest coal-fired power plant – should also help. CPS Energy’s coal plants are the single largest source of ozone-forming pollutants in Bexar County.

Wheeler, a former industry lobbyist who took over Pruitt’s job after his resignation, referenced Deely’s closure and pollution wafting over the border in his statement.

“Analysis from Texas about the role of international emissions, including from Mexico, and the pending closure of a coal-fired power plant in Bexar County will help ensure that implementation of this standard has minimal burdens on economic development,” Wheeler said.

San Antonio’s ozone levels have been declining over the past 20 years largely because of advances in vehicle technology, even as the city’s population has grown.

San Antonio would have met a 75-parts-per-billion ozone standard set in 2008, but the Obama-era EPA ratcheted it down to 70 parts per billion in 2015 in response to public health concerns.

In May, the EPA announced it would begin a review of the ozone standard to meet a Clean Air Act deadline of October 2020.

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