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EPA Continues Efforts to Understand Effects of Oxides of Nitrogen on Human Health - First NAAQS Scientific Support Document Prepared Under New Development Process

Release Date: 08/31/2007
Contact Information: Suzanne Ackerman, (202) 564-4355 /

(8/31/07) Today EPA released for public comment and independent expert peer review the first 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 ISAHealth Criteria was prepared as part of the review of the primary or human health-based NAAQS for oxides of nitrogen. 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 review process for the current primary (health-based) NAAQS for oxides of nitrogen, last reviewed in 1996, is the first using the agency's revised process for reviewing and setting the Nation's National Ambient Air Quality Standards. A review of the secondary NAAQS (based on ecological or welfare effects) for oxides of nitrogen is being conducted independently, in conjunction with a review of the secondary NAAQS for sulfur oxides. In December 2006, EPA announced changes to the review process including the creation of one integrated plan early in process that identifies key policy-relevant science issues and the replacement of the voluminous Air Quality Criteria Documents with a more concise synthesis of the most policy-relevant science called an Integrated Science Assessment or ISA. The revised process also calls for the development of continuous identification and evaluation of new science and the creation of a state-of-the-art electronic database to catalog new studies. EPA expects that this revised and streamlined process will help to improve 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.

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

Technical Contact: Dr. Mary Ross, NCEA/ORD; 919-541-5170;

View the first external review draft of the Integrated Science Assessment for Oxides of Nitrogen—Health Criteria: