Area Designations for the Federal 8-Hour Ozone Standard

This page reviewed August 7, 2017

Current Activities:

US EPA Finalizes New 8-Hour Ozone Standard:
On October 1, 2015, U.S. EPA lowered the federal 8-hour primary and secondary ozone standard from 0.075 parts per million (ppm) to 0.070 ppm. The updated standard will improve public health protection, particularly for at-risk groups including children, older adults, people of all ages with lung diseases such as asthma, and people who are active outdoors, both for recreational and work purposes. It will also improve the health of trees, plants, and ecosystems. More information on the standard, including a number of factsheets and the U.S. EPA implementation memo can be found on the U.S. EPA Ground-Level Ozone Regulatory Actions website.

As the first step in the implementation process, ARB is required to recommend initial area designations to U.S. EPA by October 1, 2016. CARB staff prepared a Staff Report that summarizes initial area designation recommendations, which was approved at a September 22, 2016 meeting of the Air Resources Board and submitted to U.S. EPA.  U.S. EPA is required to promulgate final area designations by October 1, 2017.

For questions regarding Ozone Designations please contact Craig Anderson at (916) 324-0550 or Gayle Sweigert at (916) 322-6923

Documentation / Previous Activities:

Below you will find links to ARB meeting notices, staff reports, and transmitted documents, as well as final Federal Register Notices issued by U.S. EPA.

US EPA Finalizes Clean Data Findings for 1997 Federal 8-Hour Ozone Standard:
On December 3, 2012, U.S. EPA published a final notice determining the following 7 areas had attained the 1997 federal 8-hour ozone standard:  Amador and Calaveras Counties (Central Mountain Counties), Chico (Butte County), Eastern Kern County (Mojave Desert Air Basin portion of County), Mariposa and Tuolumne Counties (Southern Mountain Counties), Western Nevada County, Sutter County (Sutter Buttes), and Ventura County (excluding the Channel Islands -- Anacapa and San Nicolas islands) (Federal Register Notice published December 3, 2012; Final Rule effective January 2, 2013).

US EPA Finalizes Area Designations and Classifications for 2008 Federal 8-Hour Ozone Standard:
On April 30, 2012, U.S. EPA issued final area designations and classifications for the 2008 (0.075 ppm) 8-hour ozone standard. The designations include two new nonattainment areas -- Eastern San Luis Obispo County and the Tuscan Buttes area of Tehama County. The area designations and classifications will be effective July 20, 2012.

U.S. EPA Submittal -- Initial ARB Recommended Area Designations for the 2008 Federal 8-Hour Ozone Standard:
On March 12, 2009, ARB submitted its area designation recommendations for the revised federal 8-hour ozone standard, based on ozone air quality data collected during 2006 through 2008. As initially recommended, there were 21 nonattainment areas, including all areas that were nonattainment for the federal 1997 8-hour ozone standard and 6 new or expanded areas. In addition to the nonattainment areas, ARB recommended 12 areas be designated as attainment and 5 areas be designated as unclassified.

NOTE:  The links below relate to the initial area designation recommendations. However, U.S. EPA made the final area designations and classifications based on more current data. I

NOTE:  Although ARB submitted exceptional events documentation for Northern California ozone data impacted by the 2008 wildfires, U.S. EPA did not act on the submittal.  Furthermore, because final area designations for the 2008 federal ozone standard were based on more recent data, there was no reason to exclude the impacted data for designation or classification purposes.  

U.S. EPA guidance allows air quality data affected by exceptional events to be excluded from the regulatory process. During the summer of 2008, a number of large wildfires burned throughout California, and smoke from these fires impacted ozone concentrations. Per U.S. EPA rules, ARB submitted documentation for exceptional events that occurred during the 2008 calendar year by March 12, 2009. A link to the documentation package is provided below. 

Exceptional Events Documentation for Shasta County:

Exceptional Events Documentation for Other Northern California Areas: