Air Quality in North Texas

  1. Air Facts
  2. Air North Texas
  3. Take Action

DFW Ozone Non-Attainment AreaMap of ozone non-attainment counties

10 counties are classified by the Environmental Protection Agency (EPA) as moderate non-attainment for 8-hour ozone levels: Collin County, Dallas County, Denton County, Ellis County, Johnson County, Kaufman County, Parker County, Rockwall County, Tarrant County and Wise County.

How does Ozone form?

Ozone forms when nitrogen oxides (NOx) and/or volatile organic compounds (VOCs) combine with sunlight and intense heat. Primary emissions sources include:

  • On-road vehicles (cars, trucks and buses)
  • Off-road vehicles (construction equipment, lawn equipment, aircraft and locomotives)
  • Point sources (cement and power plants)
  • Area sources (oil and gas drilling, bakeries, paint shops and dry cleaners)
  • Biogenic sources (vegetation and forest fires)

Historical emphasis has indicated that NOx reductions are the most appropriate way the region can lower ozone levels. Of the emissions sources listed above, on-road vehicle activities account for nearly half of the NOx inventory.

Watch our What is Ozone? video.

High Ozone Concentrations Can Cause Health Problems

Inhaling ground-level ozone is especially dangerous for people who have asthma or respiratory problems, and they may experience increased frequency of asthma attacks and health care needs.  Young children may also be at risk for developmental problems associated with ozone exposure. Asthma rates have more than doubled over the last 20 years. People without respiratory problems or asthma can also experience health effects from ozone exposure:

  • Coughing
  • Throat irritation
  • Pain, burning or discomfort when taking a deep breath
  • Chest tightening
  • Shortness of breath

More information about the health impacts of ozone exposure is available from the EPA and American Lung Association

Air Quality Index

The Air Quality Index commonly known as the AQI is an index used for reporting daily air quality levels. Colors indicate how polluted the air is and how to protect your health. It is important to know the air quality index to better understand the severity of pollution and related health impacts.

Air quality index values and ozone concentration table

More information about the air quality index is available at and Sign up to receive Air Pollution Action (Watch) Day Alerts to know when the region’s air quality may be unhealthy or worse.