Integrated Science Assessment (ISA) for Oxides of Nitrogen

Integrated Science Assessments (ISAs) provide a comprehensive and up to date evaluation and synthesis of the policy-relevant scientific literature and serve as the scientific foundation for establishing and reviewing the primary (health-based) and secondary (welfare-based) national ambient air quality standards (NAAQS). The Integrated Science Assessment for Oxides of Nitrogen – Health Criteria provides the U.S. EPA’s evaluation and synthesis of the scientific evidence related to the health effects of exposure to gaseous oxides of nitrogen. The last ISA assessing the health effects of gaseous oxides of nitrogen was released in 2016. The 2016 ISA served as the foundation for the review of the primary NAAQS for oxides of nitrogen completed in 2018.  

Oxides of nitrogen comprise a group of highly reactive gases that includes nitrogen dioxide (NO₂); nitric oxide (NO); gaseous forms of nitrous acid; gases produced from reactions involving NO (HONO), NO₂ and nitric acid (HNO₃); and other oxidized nitrogen compounds. Nitrogen dioxide is the indicator for the primary NAAQS intended to protect public health against exposures to this broader group of gaseous oxides of nitrogen. Nitrogen dioxide 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, exposure to oxides of nitrogen has been linked with a number of adverse human health effects, most notably on the respiratory system. 

The Most Recent Final ISA for Nitrogen Oxides – Health Criteria:  Integrated Science Assessment (ISA) for Oxides of Nitrogen – Health Criteria (pdf) (19.82 MB, January 2016, EPA/600/R-15/068)

Additional Resources