Air Quality Alerts Prompt Texans to Limit Vehicle Use

The National Weather Service has issued air quality alerts for millions of Texans, advising them to minimize vehicle use on Monday. These alerts affect the Dallas-Fort Worth area and the regions of Houston, Galveston, and Brazoria. The primary concern is elevated ozone levels, a hazardous air pollutant.

Reducing Ozone Pollution

Residents can help decrease ozone pollution through several actions such as carpooling, walking, biking, bringing lunch from home, avoiding drive-through lanes, conserving energy, and ensuring vehicles are well-maintained. The alerts denote Ozone Action Days for these areas.

The timing of Ozone Action Days aligns with periods when these regions usually face increased ozone levels. Forecasters determine this by checking if concentrations might meet or exceed the EPA’s AQI Level Orange threshold, which involves an eight-hour average of 71 parts per billion or a one-hour average of 125 ppb.

Monitoring and Coordination

To identify these patterns, Texas Commission on Environmental Quality (TCEQ) meteorologists rely on historical data, weather patterns, and predictive models. Upon issuing an Ozone Action Day, they coordinate with the National Weather Service to alert the public.

Understanding Ozone

“Ozone is a secondary pollutant, meaning it’s not emitted directly from sources, but is formed through chemical reactions,” observed AccuWeather meteorologist Brandon Buckingham.

These reactions necessitate sunlight and higher temperatures, making warmer months susceptible to ozone formation. Stagnant air hampers the dispersion of pollutants, causing ozone to accumulate to unhealthy levels.

Ozone, sometimes known as smog, forms in the atmosphere. Stratospheric ozone, found in the Earth’s upper atmosphere, acts as a shield against the sun’s ultraviolet rays. In contrast, ground-level ozone results from chemical reactions between nitrogen oxides and volatile organic compounds under sunlight.

Impact on Health

The Environmental Protection Agency (EPA) underscores that those most at risk from ground-level ozone are people with asthma, children, older adults, and individuals, like outdoor workers, who spend considerable time outside.

Ozone exposure levels can provoke coughing, sore throats, and breathing difficulties. It can exacerbate lung conditions such as asthma and chronic bronchitis, increasing the frequency of asthma attacks as well.

EPA’s Air Quality Index

The EPA’s Air Quality Index (AQI) measures air quality across the U.S. The scale, ranging from 0 to over 301, categorizes air quality from good (green) to hazardous (maroon), correlating with public health risks:

• Green—Good (0 to 50): Air quality is satisfactory with minimal risk.
• Yellow—Moderate (51 to 100): Air quality is acceptable, though sensitive individuals may be at risk.
• Orange—Unhealthy for Sensitive Groups (101 to 150): Health effects may affect those in sensitive groups.
• Red—Unhealthy (151 to 200): General health effects possible; sensitive groups at increased risk.
• Purple—Very Unhealthy (201 to 300): Health alert for all groups.
• Maroon—Hazardous (301 and higher): Emergency conditions likely affecting everyone.

Update, 5/25/2026, 5:30 a.m. ET: Additional information included.