EPA - TTN NAAQS

The Clean Air Act, which was last amended in 1990, requires EPA to set National Ambient Air Quality Standards (NAAQS) for wide-spread pollutants from numerous and diverse sources considered harmful to public health and the environment. The Clean Air Act established two types of national air quality standards. Primary standards set limits to protect public health, including the health of "sensitive" populations such as asthmatics, children, and the elderly. Secondary standards set limits to protect public welfare, including protection against visibility impairment, damage to animals, crops, vegetation, and buildings. The Clean Air Act requires periodic review of the science upon which the standards are based and the standards themselves.

EPA has set NAAQS for six principal pollutants, which are called "criteria" pollutants. They are listed below. For a summary table of the current NAAQS, click on the following link: NAAQS Table.

For further information about the current or prior review of any of the NAAQS or information related to the implementation of control programs designed to attain the standards, please go the links listed below:

Information on EPA's revised process for reviewing the NAAQS

Carbon Monoxide (CO)	Air Quality Standards	Implementation
Lead (Pb)	Air Quality Standards	Implementation
Nitrogen Dioxide (NO₂)	Primary Air Quality Standards Secondary Air Quality Standards	Implementation
Ozone (O₃)	Air Quality Standards	Implementation
Particulate Matter (PM)	Air Quality Standards	PM₁₀ Implementation PM_2.5 Implementation
Sulfur Dioxide (SO₂)	Primary Air Quality Standards Secondary Air Quality Standards	Implementation

Review of the NAAQS Process You will need Adobe Acrobat Reader, available as a free download, to view some of the files on this page. See EPA's PDF page to learn more about PDF, and for a link to the free Acrobat Reader.

April 2007 EPA further modifies the process for reviewing and setting the Agency's National Ambient Air Quality Standards (NAAQS) to include review and advice from the Clean Air Scientific Advisory Committee on the second draft risk/exposure assessment report, which will include estimated risks/exposures associated with potential alternative standards, prior to issuance of the Advanced Notice of Proposed Rulemking. Memo from EPA deputy Administrator Marcus Peacock outlining addition modifications to the new process (PDF) (2 pp, 145 KB) December 2006 memo from deputy Administrator Marcus Peacock (Attachment 1) (PDF) (3 pp, 219 KB) Revised Generic NAAQS Review Process (Attachment 2) (PDF) (1 pg, 32 KB)

December 2006 EPA announced a revised process for reviewing and setting the Agency’s National Ambient Air Quality Standards (NAAQS). These changes will help 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. Memo from EPA Deputy Administrator Marcus Peacock outlining revised process (PDF, 3 pp, 218 KB) Correspondence with the Clean Air Scientific Advisory Committee

Public Comments EPA has received the following public comments on the process the Agency uses to review its National Ambient Air Quality Standards. Note: Additional comments can be found in the Attachments to the April 3, 2006, EPA working group report on the NAAQS review process. Comments from the California Air Resources Board (PDF, 2 pp, 109 KB) Comments from the Battery Council International (PDF, 3 pp, 130 KB)

June 2006 Public Workshop EPA held a public workshop Tuesday, June 27, 2006 to discuss the process the Agency uses to review its National Ambient Air Quality Standards. The agency is examining the process to determine whether it can be strengthened and streamlined. In April, an agency workgroup issued recommendations for improving the process used to review the standards. 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. List of speakers registered as of June 26, 2006 (PDF, 2 pp, 31 KB) June 27 workshop: Overview presentation by Lydia Wegman, Office of Air Quality Planning & Standards, and Kevin Teichman, Office of Research & Development. (PDF, 9 pp, 165 KB) June 7, 2006: Federal Register Notice of Public Workshop to discuss the NAAQS Process

April 3, 2006, EPA working group report on the NAAQS review process
Cover memo (PDF, 2 pp, 29 KB) Executive Summary (PDF, 4 pp, 22 KB)	Report (PDF, 41 pp, 435 KB) Attachments (PDF, 76 pp, 1124 KB)

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Review of the NAAQS Process

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