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Integrated Science Assessment (ISA) for Nitrogen Dioxide (Health Criteria)

The Issue

Nitrogen dioxide (NO2) is one of a group of highly reactive gases known as "oxides of nitrogen," or "nitrogen oxides (NOx)." Other nitrogen oxides include nitrous acid and nitric acid. EPA’s National Ambient Air Quality Standard uses NO2 as the indicator for the larger group of nitrogen oxides. NO2 forms quickly from emissions from cars, trucks and buses, power plants, and off-road equipment. In addition to contributing to the formation of ground-level ozone, and fine particle pollution, NO2 is linked with a number of adverse effects on the respiratory system.

EPA Action

EPA's NOx research efforts are focused on improving emissions estimates, determining health and ecological effects, and improving modeling capabilities. The Clean Air Act requires EPA to periodically review the science for six major air pollutants, including NOx. EPA's National Center for Environmental Assessment develops Integrated Science Assessments (ISAs) that summarize the science related to the health and ecological effects caused by these pollutants. ISAs provide a comprehensive review of the policy-relevant scientific literature published since the last National Ambient Air Quality (NAAQS) review and are a critical part of the scientific basis for establishing the NAAQS.

In 2016, EPA released an update to the 2008 version of the Integrated Science Assessment for Oxides of Nitrogen- Health Criteria (Final). In 2008, the Integrated Science Assessment for Sulfur - Health Criteria (Final) was also released. Because of the overlap of these two air pollutants in the environment, the reports were combined into a single ecological criteria report, called the Integrated Science Assessment for Oxides of Nitrogen and Sulfur - Ecological Criteria (Final).

History of the NOx Health Criteria Assessments

Date Milestone
Jan 2016 EPA released the document Integrated Science Assessment for Oxides of Nitrogen - Health Criteria (Final, 2016) (EPA/600/R-15/068). This is the latest version. [Federal Register Notice: Jan 28, 2016]
Jul 2008 EPA released the document Integrated Science Assessment for Oxides of Nitrogen - Health Criteria (Final, 2008) (EPA/600/R-08/071).
Aug 1993 EPA released the document Air Quality Criteria for Oxides of Nitrogen (Final, 1993) (EPA/600/8-91/049).
1982 EPA released the document Air Quality Criteria for Oxides of Nitrogen (Final, 1982) (EPA/600/8-82/026).

Peer Review Literature

While working on the draft assessment of nitrogen oxide - health criteria (2015), EPA used the Health and Environmental Research Online (HERO) database to augment the underlining literature to support the final assessment.

See: ISA-NOx -Primary Health (2015) Project Page