Integrated Science Assessment (ISA) for Oxides of Nitrogen – Health Criteria (Second External Review Draft, 2008)

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EPA has announced that the Second External Review Draft of the Integrated Science Assessment (ISA) for Oxides of Nitrogen – Health Criteria has been made available for independent peer review and public review. This draft ISA document represents a concise synthesis and evaluation of the most policy-relevant science and will ultimately provide the scientific bases for EPA’s decision regarding whether the current standard for NO2 sufficiently protects public health.

EPA has released for public comment and independent expert peer review the second external review draft of a document entitled, Integrated Science Assessment for Oxides of Nitrogen – Health Criteria. Oxides of nitrogen is one of six principal (or criteria) pollutants for which EPA has established national ambient air quality standards (NAAQS). The Clean Air Act requires EPA to periodically review the scientific basis for these standards by preparing an Integrated Science Assessment (ISA), formerly called an Air Quality Criteria Document (AQCD). The draft ISA was prepared as part of the review of the primary or human health-based NAAQS for oxides of nitrogen. The draft ISA evaluates and integrates the newly available health evidence, and contains the key information and judgments formerly found in the AQCD. A series of Annexes to the draft ISA provides more extensive and detailed summaries of the most pertinent scientific literature. This is EPA’s latest evaluation of the scientific literature on the potential adverse health effects resulting from exposures to oxides of nitrogen, particularly nitrogen dioxide or NO2. There are significant new data, particularly epidemiological studies, that strengthen the evidence for these effects since the last scientific review document was released in 1993.


The Clean Air Act (CAA) requires EPA to periodically review and revise, as appropriate, existing air quality criteria and NAAQS. The CAA also requires an independent scientific committee to review the criteria and to advise the Administrator regarding any recommended revisions to the existing criteria and standards, as may be appropriate. The Clean Air Scientific Advisory Committee (CASAC) of EPA’s Science Advisory Board serves as this independent scientific committee. The ISA is one of the four major elements of the NAAQS review process that will inform the Agency’s final decisions; other components of the process are an integrated plan highlighting the key policy-relevant issues; a risk/exposure assessment; and an advance notice of proposed rulemaking (ANPRM) reflecting the Agency’s views regarding options to retain or revise the NOx NAAQS based on the evaluation of key information contained in the ISA and Risk/Exposure Assessment, as well as additional appropriate technical analysis.


The second draft ISA will be reviewed by the Clean Air Scientific Advisory Committee(CASAC) at a public meeting later this year. A final ISA will be released in 2008, which will address CASAC and public comments received on the second draft ISA. Once final, the complete ISA will be posted on the EPA Web site to provide the scientific bases for EPA’s periodic review and possible revision of the primary NAAQS for oxides of nitrogen.


U.S. EPA. Integrated Science Assessment (ISA) for Oxides of Nitrogen – Health Criteria (Second External Review Draft, 2008). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-07/093aB, 2008.


Date Description
01-1982EPA released the document Air Quality Criteria for Oxides of Nitrogen.
02-Aug 1993EPA released the final report on the Air Quality Criteria Document for Oxides of Nitrogen.
03-Dec 2005EPA published a Call for Information on Oxides of Nitrogen in the December 9, 2005 Federal Register Notice.
04-Feb 2007EPA hosted a workshop on the assessment of health science for the review of the NAAQS for Nitrogen (NOx) and Sulfur Oxides (SOx).
05-Aug 2007EPA releases the First External Review Draft for an External Peer Review and public comment.
06-Oct 2007EPA hosts a Science Advisory Board (SAB) CASAC Meeting and external peer review to review and discuss the draft report.
07-Mar 2008EPA releases the Second External Review Draft for external review and public comment.

Additional Information

Included for public review is the draft Integrated Science Assessment for Oxides of Nitrogen - Health Criteria (Second External Review Draft). Comments on this document may be submitted and reviewed using the e-Government Web site. From the site, select Environmental Protection Agency and the keyword EPA-HQ-ORD-2005-0029 (for the docket ID) to comment on this report.