Air Quality Standards and Area Designations

This page reviewed December 21, 2012

WHAT'S NEW


On December 14, 2012, U.S. EPA lowered the federal primary PM2.5 annual standard from 15.0 micrograms per cubic meter to 12.0 micrograms per cubic meter.  The new annual standard will be come effective 60 days after publication in the Federal Register.  U.S. EPA made no changes to the primary 24-hour PM2.5 standard or to the seconday PM2.5 standards.

On December 3, 2012, U.S. EPA published a final notice in the Federal Register 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).  The rule is effective January 2, 2013.  

On November 15, 2012, the Air Resources Board approved a revision to the infrastructure portion of California's State Implementation Plan (SIP).  The proposed Infrastructure SIP was developed in response to U.S. EPA's January 2010 revision to the federal nitrogen dioxide standard and describes the State's resources, programs, and authority to implement and enforce the standard.  Additional information is available on ARB's SIP webpage.

On July 20, 2012, the Air Resources Board released a Notice of Public Comment Period on Proposed Amendments to the Area Designations for State Ambient Air Quality Standards as well as the Initial Statement of Reasons for Rulemaking: Proposed 2012 Amendments to Area Designations for State Ambient Air Quality Standards for public comment.  Additional information about these items can be found on the 2012 State Area Designations webpage.

On May 24, 2012, the Air Resources Board approved a revision to the State Implementation Plan (SIP) to address attainment of the federal lead standard in the South Coast Air Basin portion of Los Angeles County. This is the only area in California designated as nonattainment for lead. The SIP revision has been submitted to U.S. EPA for approval. Additional information about this item is found on ARB's South Coast Plans webpage.

 On April 30, 2012, U.S. EPA issued final area designations and classifications for the 2008 federal 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. 


Background:

map The Air Resources Board (ARB or Board) has established State ambient air quality standards (State standards) to identify outdoor pollutant levels considered safe for the public. After State standards are established, State law requires ARB to designate each area as attainment, nonattainment, or unclassified for each State standard. The area designations, which are based on the most recent available data, indicate the healthfulness of air quality throughout the State. Further information can be found on the State Standard Area Designations page. 

In addition to State standards, the Federal Clean Air Act requires the United States Environmental Protection Agency (U.S. EPA) to set national ambient air quality standards (federal standards or national standards). The federal area designation maps and tables reflect these federal standards. Further information about the federal standards and area designations can be found on the Federal Standard Area Designations page.
 



We maintain an e-mail mailing list for Area Designation activities. As announcements, reports, and other information are posted to this website, we will send e-mail notifications to everyone on the list. If you wish to receive these notices, you can subscribe by visiting the Area Designations List Serve web page and following the instructions there.

STATE STANDARD AREA DESIGNATIONS


Health and Safety Code (H&SC) section 39607(e) requires the Board to establish and periodically review area designation criteria. H&SC section 39608 requires the Board to use these criteria to designate areas of California as attainment, nonattainment, or unclassified for the State standards and to review these area designations annually. The Board makes area designations for ten pollutants: ozone, suspended particulate matter (PM10 and PM2.5), carbon monoxide, nitrogen dioxide, sulfur dioxide, sulfates, lead, hydrogen sulfide, and visibility reducing particles. The Board reviews the area designations each year and updates them as appropriate, based on the three most recent complete and validated calendar years of air quality data.

FEDERAL STANDARD AREA DESIGNATIONS


The U.S. EPA designates areas for each pollutant for which there is a national ambient air quality standard. ARB publishes maps of these area designations for informational purposes; however, the most current federal nonattainment area designations are found on the U.S. EPA website.

EXCEPTIONAL EVENTS

Exceptional events are natural or unusual events that can overwhelm existing control strategies for man-made pollution. If such an event occurs and U.S. EPA agrees with the State's exceptional events determination, data that would have caused an exceedance of a federal standard is excluded from determining compliance with the standard. Examples of exceptional events include, but are not limited to, wildfires, high winds and dust, volcanic activities, stratoshperic ozone intrusion, structural fires, and fireworks.

Exceptional Events must meet the following five criteria before being approved by either the State or U.S. EPA:

  1. The event must meet the statutory definition of an exceptional event,
  2. There must be a clear causal relationship between the event and the measured exceedance,
  3. The concentration must be higher than normal background and historical fluctuations,
  4. It must be established that the measured concentration would not have exceeded the standard, "but-for" the event, and
  5. The State must satisfy public process and review procedures.

ARB provides an opportunity for public review and comment on the exceptional events documentation before submitting it to U.S. EPA for final approval. 


Comments related to PM2.5 and PM10 exceptional events should be directed to Sylvia Vanderspek or Theresa Najita. 
Comments related to exceptional events for all other air pollutants should be directed to Gayle Sweigert.

Contact Information

Comments and questions about area designations may be directed to:
Ms. Theresa Najita or (916) 322-7297

Comments and questions about air quality standards may be directed to:
Dr. Linda Smith or (916) 327-8225

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