In 1997, the U.S. Environmental Protection Agency (EPA) announced new national ambient air quality standards (NAAQS) for ground-level ozone, the primary constituent of smog. The new standard was challenged in the federal courts. The standard was upheld by the courts, but the EPA is required to revise their implementation plan. In the interim, EPA has re-instated the old one-hour standard but has not yet made public it's revised implementation plan.

The new eight-hour standard of 0.08 parts per million (85 parts per billion to exceed the standard) is determined by the fourth highest eight-hour daily maximum at any single monitor in an area, averaged over a three-year period.

The previous one-hour standard of 0.12 parts per millions (125 parts per billion to exceed) was re-instated and currently applies to all areas.

Information about the court rulings on the new eight-hour standard can be obtained from the EPA's Office of Air and Radiation.

Additional information about the revised ozone standard may be obtained from the EPA.

• Measure the highest 8-hour ozone readings each day of the year.
• For each year, rank these values from highest to lowest.
• For each year of three consecutive years, determine the fourth-highest value.
• Average the fourth-highest values from all three years.
• Compare this average to the standard. If it exceeds the standard, the area is in nonattainment

To see most current 8-hour average data click here.

To see  the design value history for Austin MSA area click here or click  ozone trend link below in order to see historical ozone data and and the trend approximation.

Ozone Trends

Click here to see 8-hr ozone trends in the Austin area

Click here to see ozone trends in the Austin MSA overlaid with the population estimate.