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North Texas' air quality problem
requires regional solutions

Nonattainment classification for 8-hour ozone levels
In 2012, the US Environmental Protection Agency (EPA) designated ten counties in North Central Texas as nonattainment for the 2008 eight-hour ozone National Ambient Air Quality Standard (NAAQS). These standards are designed to protect human and environmental health, and ground-level ozone is monitored and targeted for reductions due to its potentially harmful effects.

Collin County
Dallas County
Denton County
Ellis County
Johnson County
Kaufman County
Parker County
Rockwall County
Tarrant County
Wise County

Nonattainment area


In 2014, the region's ozone concentration fell within the previous eight-hour ozone standard of less than 85 parts per billion for the first time, which represents significant progress for the region. The North Central Council of Governments will continue to work with partners and encourage the involvement of residents and employers to meet the current standard of 75 ppb to ensure a good quality of life for people of all ages.

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 such as cars, trucks and buses.
    • Off-road vehicles such as construction equipment, lawn equipment, aircraft and locomotives.
    • Point sources such as cement and power plants.
    • Area sources such as oil and gas drilling, bakeries, paint shops and dry cleaners.
    • Biogenic sources like 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.

The Regional Transportation Council developed a list of the most detrimental activities for the region's air quality. Programs, policies and projects focus on reducing emissions from:

    • High-emitting vehicles
    • Cold starts
    • Hard accelerations
    • High speeds
    • Low speeds
    • Excessive idling
    • Diesel engines
    • Vehicle miles traveled

Learn more about what you can do to reduce emissions. More information about air quality programs, policies and projects is available through NCTCOG and partner agencies.

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 health impacts of ozone exposure is available from the EPA and American Lung Association.

Know the air quality index to better understand the severity of pollution and related health impacts
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.

Air Quality Index

More information about the air quality index is available from NCTCOG, EPA, and others. Sign up to receive Ozone Action Day Alerts to know when the region's air quality may be unhealthy or worse.

 carpooling pollutes less than driving alone

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