Ozone Action Days: What are they, why is San Antonio seeing more & should we be concerned?

San Antonio saw 4 ozone action days is just one week

The city of San Antonio had the most consecutive ozone action days ever last week – four, to be exact.

SAN ANTONIO – The city of San Antonio had the most consecutive ozone action days ever last week – four, to be exact.

What is ozone?

Ozone is a colorless, unstable toxic gas and was a big part of what used to be called smog.

Ozone occurs when nitrogen oxide – emissions from power plants, cars, lawnmowers are just some examples – mix with volatile organic compounds such as benzene found in paints, acetone and formaldehyde.

The sun then comes into play.

When sun rays – not heat – combine with those chemicals, it creates ozone.

In 2015, the Environmental Protection Agency set the ozone standard levels to 70 parts per billion.

What does that look like? The 70 parts per billion are not as much if compared to all our surrounding air, but it is still enough to be harmful.

When do Ozone Action Days occur?

Ozone Action Days occur when there is a weather prediction of sun, very little wind and clear skies.

This type of weather essentially traps the ozone or secondary pollutants in our air.

With nowhere to go, additional toxic gas can be created and lead to the ozone standard levels exceeding the standard 70 parts per billion.

Who decides when they happen?

The Texas Commission on Environmental Quality decides on these days.

Wendall Hardin is the Ozone Attainment program manager for San Antonio who helps get the word out locally.

Hardin said during Ozone Action Days, people with asthma and/or chronic obstructive pulmonary disease, or COPD should try to stay inside from noon to 7 p.m. when ozone levels are its highest. Parents of newborns should try to avoid exposing their children to the bad air, too.

"We have a lot of heavy air here, (such as) humidity (and) just catching that ozone ... it's just hanging in the air just catching into your lungs, causing everybody a problem," Hardin said.

Are we seeing more Ozone Action Days?


San Antonio had five ozone action days in 2017, with the following year seeing 10.

So far, San Antonio has had seven ozone action days, with four being just last week.

Hardin said there a couple of reasons for that increase. One of those reasons is the city's population is growing.

More people means more ozone, Hardin said, adding that the city is seeing more clear, sunny days with little wind.

"We are starting to see El Nino come through about every two years," Hardin said. "It used to be every six years to seven years. So, what we are seeing are those wind patterns coming through, that's kind of throwing off every couple of years."

Hardin said residents should want to see fewer ozone action days for health reasons, and also to be in good standing with the EPA.

If our ozone levels get too high, Hardin said the federal government could start setting stricter regulations or even fine Bexar County.

How can you do your part?

Anyone can do your part on ozone action days by not idling their car, filling gas tanks up after 6 p.m., doing less (gas-powered) lawn mowing and using mass transit.

A second opinion

In addition, KSAT meteorologist Sarah Spivey shared her opinion on how concerned we should be when it comes to ozone action days.

Spivey said ozone action days are very valid and that we should follow the suggested restrictions.

Not following the restrictions can affect people with respiratory problems but it should not keep people from doing their daily activities.

"But I do want to caution people that you shouldn't just read an Ozone Action Day as, 'Beware, don't go outside,'" Spivey said. "You should do a little research, it's really not that dangerous to go outside on Ozone Action Days."

About the Authors:

Sarah Acosta is a weekend Good Morning San Antonio anchor and a general assignments reporter at KSAT12. She joined the news team in April 2018 as a morning reporter for GMSA and is a native South Texan.

Before starting at KSAT in August 2011, Ken was a news photographer at KENS. Before that he was a news photographer at KVDA TV in San Antonio. Ken graduated from San Antonio College with an associate's degree in Radio, TV and Film. Ken has won a Sun Coast Emmy and four Lone Star Emmys. Ken has been in the TV industry since 1994.