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The revised air quality criteria document for oxides of nitrogen (NOx) reviews and evaluates the scientific information on the health and welfare effects associated with exposure to concentrations of NO2 found in ambient air. Although the document is not intended to be an exhaustive literature review, it is intended to cover all the pertinent literature through early 1991. The references cited in this document are, therefore, reflective of the current state of knowledge of those issues relevant to the subsequent review of the National Ambient Air Quality Standards (NAAQS) for NO2, currently set at 0.053 ppm (100 ug/m3), as an annual average. Gaps in knowledge are identified. Although emphasis is placed on the presentation of data on health and welfare effects, other scientific data are presented and evaluated in order to provide a better understanding of the properties and principles of formation, sources and emissions, atmospheric transport and transformation, measurement methods, ambient air concentrations, effects on crops and natural vegetation, effects on the terrestrial and aquatic ecosystems, effects on visibility, effects on materials, and health effects. Health effects include information derived from experimental toxicological studies of animals, epidemiological studies, and human clinical studies.


U.S. EPA. AIR QUALITY CRITERIA FOR OXIDES OF NITROGEN (External Review Draft, 1991). U.S. Environmental Protection Agency, Washington, D.C., EPA/600/8-91/049aA (NTIS PB92176361), 1991.

Additional Information

This draft document has been superseded by the final document: Air Quality Criteria for Oxides of Nitrogen, EPA 600/8-91-049aF

This document has been reviewed in accordance with U.S. Environmental Protection Agency policy and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.