Harris County is a designated nonattainment area for the EPA’s 8-hour ozone standard. Harris County and other state and local agencies participate in maintaining a monitoring network to provide the public with current ozone data and advisories.

Ozone (O₃) is a compound containing three oxygen atoms. Molecules of normal oxygen (O₂) are composed of two oxygen atoms. Ozone can be found in the upper atmosphere and at ground level. It occurs naturally in the upper atmosphere where it blocks harmful UV radiation. It forms at ground level when pollutants react to form photochemical smog. Ozone is highly reactive and at high concentrations it may corrode metals, degrade plastics, and cause respiratory irritation.

Ozone Formation

Ozone forms at ground level when nitrogen oxides (NO_x) and volatile organic compounds (VOC) combine in the presence of sunlight. NO_x is found in car exhaust and industrial emissions. VOC enters the atmosphere from industrial emissions, paints and solvents, evaporated gasoline, and natural sources. The ideal conditions for ozone formation are hot, clear days with calm winds.

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What to do when ozone levels are high

Ground level ozone can cause inflammation of the lungs. Some studies have also linked ozone exposure to increased incidence of heart attack and respiratory infection. Sensitive individuals such as people with respiratory conditions, parents of young children, and the elderly should pay close attention to ozone warnings and avoid outdoor activity when ozone levels are high. Strenuous outdoor exercise should also be avoided when ozone levels are high.

You can assist in reducing ozone levels in Harris County. Maintain your vehicle to reduce emissions. Fill your gas tank and mow your lawn in the evening when ozone formation is low. Use public transportation where available. Conserve electricity to reduce emissions from power plants. It will take the cooperation of the public, industry, and regulatory agencies to restore our air quality in Harris County. Thank you for doing your part.

Air Quality Links  

​Ozone Links