Integrated Science Assessment (ISA) for Oxides of Nitrogen and Sulfur - Environmental Criteria (Second External Review Draft, Aug 2008)
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Abstract
EPA has announced that the Second External Review Draft of the Integrated Science Assessment (ISA) for Oxides of Nitrogen and Sulfur - Environmental Criteria has been made available for independent peer review and public review. This draft ISA document represents a concise synthesis and evaluation of the most policy-relevant science and will ultimately provide the scientific bases for EPA's decision on retaining or revising the current secondary standards for NO2 and SO2.Oxides of nitrogen and oxides of sulfur are two 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 previous scientific review documents for oxides of nitrogen and sulfur were released in 1993 and 1982, respectively.
This draft ISA was prepared as part of the joint review of the secondary or welfare-based NAAQS for oxides of nitrogen and sulfur. The draft ISA evaluates and integrates the newly available environmental evidence, and contains the key information and judgments formerly found in the AQCD. A series of Annexes to the draft ISA provides more extensive and detailed summaries of the most pertinent scientific literature. This is EPA’s latest evaluation of the scientific literature on the potential adverse environmental effects resulting from exposures to oxides of nitrogen and sulfur. There are significant new data, particularly with regards to acidification and nitrogen enrichment, that strengthen the evidence for these effects since the last scientific review documents were released.
Impact/Purpose
The current secondary NAAQS for SOX, set in 1973, is a 3-h average 0.5 ppm of SO2, not to be exceeded more than once per year. The secondary NOX NAAQS is identical to the primary standard set in 1971: 0.053 ppm NO2 as an annual average. These secondary standards are intended to protect against direct damage to vegetation by exposure to gas-phase NOX or SOX. Acute and chronic exposures to SO2 can have phytotoxic effects on vegetation, such as foliar injury, decreased photosynthesis and decreased growth. Similarly, exposure to sufficient concentrations of NO2, NO, PAN, and HNO3 can cause foliar injury, decreased photosynthesis and decreased growth. In addition, these gas-phase NOX may contribute to N saturation in some areas of the U.S. There is little new evidence overall for direct effects of exposure to gas-phase NOX or SOX on vegetation at current concentrations. However, there is some evidence that vegetation in regions with high concentrations of photochemical oxidants may be affected by HNO3 exposure.Citation
U.S. EPA. Integrated Science Assessment (ISA) for Oxides of Nitrogen and Sulfur - Environmental Criteria (Second External Review Draft, Aug 2008). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-08/082, 2008.History/Chronology
| Date | Description |
|---|---|
| 01- 1982 | EPA released the document Air Quality Criteria for Oxides of Nitrogen and the Air Quality Criteria for Particulate Matter and Sulfur Oxides. |
| 02- Aug 1993 | EPA released the final document Air Quality Criteria for Oxides of Nitrogen. |
| 03- Dec 2005 | EPA published a Call for Information on Oxides of Nitrogen in a December 9, 2005 Federal Register Notice. |
| 04- May 2006 | EPA put out a call for related information in a May 15, 2006 Federal Register Notice to update the science assessment for sulfur oxides. |
| 05- July 2007 | EPA hosted a workshop on the assessment of environmental and welfare effects science for the review of the secondary NAAQS for Oxides of Nitrogen and Sulfur. |
| 06- Aug 2007 | EPA released the draft document, Integrated Science Assessment (ISA) for Oxides of Nitrogen – Health Criteria (Second External Review Draft). |
| 07- Sep 2007 | EPA released the draft document, Integrated Science Assessment (ISA) for Sulfur Oxides - Health Criteria and the Annexes (Second External Review Draft). |
| 08- Dec 2007 | EPA releases the Integrated Science Assessment (ISA) for Oxides of Nitrogen and Sulfur Environmental Criteria (First External Review Draft) for an external peer review and public comment. |
| 09- Feb 2008 | EPA releases the Annexes for the Integrated Science Assessment (ISA) for Oxides of Nitrogen and Sulfur Environmental Criteria (First External Review Draft). |
| 10- Aug 2008 | EPA releases the Second External Review Draft of the Integrated Science Assessment (ISA) for Oxides of Nitrogen and Sulfur – Environmental Criteria document for an external peer review and public comment. |
| 11- Sep 2008 | EPA extended the deadline for public comment to October 10, 2008, for both of these documents. |
Additional Information
Included for public review is the draft Integrated Science Assessment (ISA) for Oxides of Nitrogen and Sulfur – Environmental Criteria (Second External Review Draft). Comments on this document may be submitted and reviewed using the e-Government Regulations.gov Web site. From the site, select Environmental Protection Agency and the keyword EPA-HQ-OAR-2007-1145 (for the docket ID) to comment on this report. The deadline for comments is October 1, 2008.Download(s)
This download(s) is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not been formally disseminated by EPA. It does not represent and should not be construed to represent any Agency determination or policy.
- Integrated Science Assessment for Oxides of Nitrogen and Sulfur – Environmental Criteria (Second External Review Draft) (PDF) (659 pp, 21.8 MB, about PDF)
- Integrated Science Assessment for Oxides of Nitrogen and Sulfur - Environmental Criteria (Annexes Only) (PDF) (524 pp, 7.4 MB, about PDF)
- Key findings for the Integrated Science Assessment for Oxides of Nitrogen and Sulfur – Environmental Criteria (PDF) (4 pp, 100.6 KB, about PDF)
- Memo from the NCEA-RTP Director: Ila Cote (PDF) (3 pp, 152.3 KB, about PDF)
- CASAC Project Overview for the Review of the EPA's Integrated Science Assessment for Nitrogen Dioxide and Sulfur Dioxide Secondary (Welfare-based)
- CASAC Review of EPA’s Integrated Science Assessment (ISA) for Oxides of Nitrogen and Sulfur – Environmental Criteria (Second External Review Draft) (PDF) (74 pp, 919.9 KB, about PDF)
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