air quality

What is an Ozone Action Day?

The Texas Commission on Environmental Quality says it's an Ozone Action Day -- so now what?

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You may have heard the Texas Commission on Environmental Quality or one of NBC 5's Weather Experts say that today or tomorrow is an Ozone Action Day. But what does that mean and what should you do about it?

An Ozone Action Day is any day when the ground level of ozone, a pollutant, is forecast to be at unhealthy or hazardous levels.

According to the TCEQ, "ground-level ozone is of particular importance because it is a respiratory toxic agent that can cause acute respiratory health effects when people breathe high concentrations of it over several hours. These effects include decreased lung function and pain with deep breaths and aggravated asthma symptoms."

So, those with sensitive breathing issues should pay extra attention to ozone alerts because the increased level of pollutants could exacerbate existing medical issues.

Thankfully, we'll get some advanced warning of these high ozone days. Every day during ozone season, which runs from roughly March through November in Texas, the TCEQ forecasts the ground-ozone level for nine metropolitan areas in the Lone Star State. Those areas are Austin, Beaumont-Port Arthur, Corpus Christi, Dallas-Fort Worth, El Paso, Houston, San Antonio, Tyler-Longview, and Victoria.

"The TCEQ informs the public typically a day in advance when conditions are forecast to be favorable for high ozone levels in any of the participating areas so citizens, businesses, and industry can take steps to reduce the pollutants that contribute to ozone formation," the TCEQ said.

The TCEQ said warm, sunny days with stagnant winds allow for the highest concentrations of ground ozone to form and accumulate, which is why we'll see more Ozone Action Days in the warmer months. Other factors, such as wildfire smoke or pollutants from cars, industrial plants and refineries, can lead to increases in ground ozone.

To sign up for the TCEQ's Air Quality alerts via email or SMS, click here. For more information from the TCEQ on air quality and for ozone facts, such as how ground-level ozone is created and how it's different from stratospheric ozone, click here.


If you're wondering if you should exercise outside during Ozone Action Days, according to the Environmental Protection Agency, it depends.

The EPA said there are several factors to consider before undertaking strenuous activity outdoors during times of high air pollution including the person's health, length of workout, the intensity of the workout and, of course, the pollution level.

The EPA recommends checking the Air Quality Index on which offers a science-based guide on actions to take based on the current air forecast, including exercise. In addition to checking the AQI, the EPA also recommends you check with your doctor about what might be the best decision for you.

Generally, healthy people are able to exercise outdoors even in moderate air pollution. However, older people, and those who are sensitive to pollutants, should avoid intensive outdoor exercise with the air quality being moderate or higher, the EPA said.

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