Oxides of Nitrogen & Sulfur
The Issue
Oxides of Nitrogen and Sulfur, also referred to as NOx and SOx respectfully, is a gas that occurs both in the Earth's upper atmosphere and at ground level where it is a key component of urban smog. Ground-level ozone triggers a variety of health problems even at very low levels, may cause permanent lung damage after long-term exposure, and damages plants and ecosystems.
Peak ozone levels typically occur during hot, dry, stagnant summertime conditions. Millions of Americans live in areas where ozone levels exceed EPA's health-based air quality standards, primarily in parts of the Northeast, the Lake Michigan area, parts of the Southeast, southeastern Texas, and parts of California. Peak ozone levels typically occur during hot, dry, stagnant summertime conditions.
EPA Action
EPA's NOx and SOx research efforts are focused on improving emissions estimates, determining health and ecological effects, and improving modeling capabilities. EPA's National Center for Environmental Assessment periodically evaluates the latest research concerning the public health and welfare effects of sulfur and oxides of nitrogen andpublishes the most up-to-date findings in an assessment called an Integrated Science Assessments. In 2008, EPA released the Integrated Science Assessment for Oxides of Nitrogen- Health Criteria (Final) and the Integrated Science Assessment for Sulfur - Health Criteria (Final). But because of the overlap of these 2 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).These documents provide the scientific basis for the establishment of the most current national air quality standards. [See the history of the pollutant reports for more detailed information on the NOx/SOxassessments]
[Update] EPA has announced a draft development plan for the next Integrated Science Assessment (ISA) for the health effects of nitrogen oxides (NOX) which will serve as the scientific basis for review of the primary (health-based) National Ambient Air Quality Standard for nitrogen dioxide. [Federal Register Notice May 3, 2013]
Workshop announcements:
- 6/11: Workshop to review initial draft materials for the NOx Integrated Science Assessment for Health Effects
- 6/12-13: Workshop and Call for Information on Integrated Science Assessment for SOx (FR Notice)
Related Links
- Basic information about sulfur oxide
- Basic Information about nitrogen dioxide
- NOx Reductions Under the Acid Rain Program
- Nitrogen Oxide research at EPA (PDF) (2 pp, 262 KB, About PDF)
- Using Sulfur as a Tracer of Outdoor Fine Particulate Matter (PDF) (10 pp, 210 KB, About PDF)
- NOx and SOx regulations
- National Ozone Air Quality Forecasts
- Clean Air Act