Reviewing National Ambient Air Quality Standards (NAAQS)

Historical Information on the NAAQS Review Process

EPA’s NAAQS review process has evolved over time. Below are Agency documents regarding changes to the NAAQS review process between 2005 and 2009. Written communication between the Agency and CASAC regarding the NAAQS process can be found at the following link: Correspondence with the Clean Air Scientific Advisory Committee.

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Recognizing the importance of scientific integrity and transparency, Administrator Lisa P. Jackson reexamined the NAAQS review process and modifications to the process made in the last administration. On May 21, 2009 Administrator Jackson called for key changes to the NAAQS review process, including reinstating a policy assessment document that contains staff analyses of the scientific bases for alternative policy options for consideration by senior Agency management prior to rulemaking. This Policy Assessment document serves to “bridge the gap” between the scientific information and the judgments required of the Administrator in determining whether it is appropriate to retain or revise the standards. In conjunction with this change, EPA will no longer issue a policy assessment in the form of an Advance Notice of Proposed Rulemaking (ANPR).


In December 2005, the EPA Deputy Administrator requested that the Office of Air and Radiation (OAR) and the Office of Research and Development (ORD) conduct a “top-to-bottom review” of the process the Agency uses in setting and reviewing NAAQS. Advice and recommendations were requested from current and former members of the CASAC and other stakeholder groups that had substantial experience with the NAAQS review process. On April 3, 2006, the working group issued a report outlining their conclusions and recommendations. 

April 3, 2006, EPA working group report on the NAAQS review process

June 2006 Public Workshop
EPA held a public workshop on June 27, 2006 to discuss the process the Agency uses to review the NAAQS. The workshop provided the public the opportunity to present their views on the review process and to discuss the process with EPA officials. This workshop did not cover issues related to the ongoing review of any specific air quality standard.

Public Comments
EPA received the following public comments on the process the Agency uses to review the NAAQS. Note: Additional comments can be found in the Attachments to the April 3, 2006 EPA working group report on the NAAQS review process.

December 2006
EPA announced a revised process for reviewing and setting the Agency’s NAAQS. These changes were made to improve the efficiency of the NAAQS review process while ensuring that the Agency’s decisions are informed by the best available science in order to protect public health and the environment.

April 2007
EPA further modified the process for reviewing and setting the NAAQS to include review and advice from the CASAC on the second draft risk/exposure assessment reports, which will include estimated risks/exposures associated with potential alternative standards under consideration. 

September 2008
EPA made additional changes to the NAAQS review process based on CASAC recommendations presented in a January 23, 2008 letter to the EPA Administrator. 

Learn about the current review process.