Review of the Secondary National Ambient Air Quality Standards for Oxides of Nitrogen, Oxides of Sulfur, and Particulate Matter

<RULE> ENVIRONMENTAL PROTECTION AGENCY <CFR>40 CFR Part 50</CFR> <DEPDOC>[EPA-HQ-OAR-2014-0128; FRL-5788-05-OAR]</DEPDOC> <RIN>RIN 2060-AS35</RIN> <SUBJECT>Review of the Secondary National Ambient Air Quality Standards for Oxides of Nitrogen, Oxides of Sulfur, and Particulate Matter</SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Environmental Protection Agency (EPA). <HD SOURCE="HED">ACTION:</HD> Final rule. <SUM> <HD SOURCE="HED">SUMMARY:</HD> Based on the Environmental Protection Agency's (EPA's) review of the air quality criteria for ecological effects and secondary national ambient air quality standards (NAAQS) for oxides of nitrogen (N oxides), oxides of sulfur (SO <E T="52">X</E> ), and particulate matter (PM), the EPA is revising the existing secondary sulfur dioxide (SO <E T="52">2</E> ) standard to an annual average, averaged over three consecutive years, with a level of 10 parts per billion (ppb). Additionally, the Agency is retaining the existing secondary standards for N oxides and PM, without revision. The EPA is also finalizing revisions to the data handling requirements for the secondary SO <E T="52">2</E> NAAQS. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> This final rule is effective on January 27, 2025. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> The EPA has established a docket for this action under Docket ID No. EPA-HQ-OAR-2014-0128. All documents in the docket are listed on the <E T="03">https://www.regulations.gov</E> website. Although listed in the index, some information is not publicly available, <E T="03">e.g.,</E> CBI or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, is not placed on the internet and will be publicly available only in hard copy form. Publicly available docket materials are available electronically through <E T="03">https://www.regulations.gov.</E> <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Ms. Ginger Tennant, Environmental Protection Agency, Health and Environmental Impacts Division, Office of Air Quality Planning and Standards (mail code C539-04), Research Triangle Park, NC 27711; telephone number: (919) 541-4072; email address: <E T="03">tennant.ginger@epa.gov.</E> </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> <HD SOURCE="HD1">Table of Contents</HD> <EXTRACT> <FP SOURCE="FP-2">Executive Summary</FP> <FP SOURCE="FP-2">I. Background</FP> <FP SOURCE="FP1-2">A. Legislative Requirements</FP> <FP SOURCE="FP1-2">B. Related Control Programs</FP> <FP SOURCE="FP1-2"> C. History of the Secondary Standards for N Oxides, SO <E T="52">X</E> and PM </FP> <FP SOURCE="FP1-2">1. N Oxides</FP> <FP SOURCE="FP1-2"> 2. SO <E T="52">X</E> </FP> <FP SOURCE="FP1-2">3. Related Actions Addressing Acid Deposition</FP> <FP SOURCE="FP1-2"> 4. Most Recent Review of the Secondary Standards for N Oxides and SO <E T="52">X</E> </FP> <FP SOURCE="FP1-2">5. PM</FP> <FP SOURCE="FP1-2">D. Current Review</FP> <FP SOURCE="FP-2">II. Rationale for Decisions</FP> <FP SOURCE="FP1-2">A. Introduction</FP> <FP SOURCE="FP1-2">1. Background</FP> <FP SOURCE="FP1-2">a. Basis for Existing Secondary Standards</FP> <FP SOURCE="FP1-2">b. Prior Review of Deposition-Related Effects</FP> <FP SOURCE="FP1-2">c. General Approach for This Review</FP> <FP SOURCE="FP1-2">2. Overview of Air Quality and Deposition</FP> <FP SOURCE="FP1-2"> a. Sources, Emissions and Atmospheric Processes Affecting SO <E T="52">X</E> , N Oxides and PM </FP> <FP SOURCE="FP1-2">b. Recent Trends in Emissions, Concentrations, and Deposition</FP> <FP SOURCE="FP1-2">c. Relationships Between Concentrations and Deposition</FP> <FP SOURCE="FP1-2">3. Overview of Welfare Effects Evidence</FP> <FP SOURCE="FP1-2">a. Nature of Effects</FP> <FP SOURCE="FP1-2"> (1) Direct Effects of SO <E T="52">X</E> and N Oxides in Ambient Air </FP> <FP SOURCE="FP1-2">(2) Acid Deposition-Related Ecological Effects</FP> <FP SOURCE="FP1-2">(3) Nitrogen Enrichment and Associated Ecological Effects</FP> <FP SOURCE="FP1-2">(4) Other Deposition-Related Effects</FP> <FP SOURCE="FP1-2">b. Public Welfare Implications</FP> <FP SOURCE="FP1-2">c. Exposure Conditions and Deposition-Related Metrics</FP> <FP SOURCE="FP1-2">(1) Acidification and Nitrogen Enrichment in Aquatic Ecosystems</FP> <FP SOURCE="FP1-2">(2) Deposition-Related Effects in Terrestrial Ecosystems</FP> <FP SOURCE="FP1-2"> (3) Other Effects of N Oxides, SO <E T="52">X</E> and PM in Ambient Air </FP> <FP SOURCE="FP1-2">4. Overview of Exposure and Risk Assessment for Aquatic Acidification</FP> <FP SOURCE="FP1-2">a. Key Design Aspects</FP> <FP SOURCE="FP1-2">b. Key Limitations and Uncertainties</FP> <FP SOURCE="FP1-2">c. Summary of Results</FP> <FP SOURCE="FP1-2">B. Conclusions</FP> <FP SOURCE="FP1-2">1. Basis for Proposed Decision</FP> <FP SOURCE="FP1-2">a. Policy-Relevant Evaluations in the Policy Assessment</FP> <FP SOURCE="FP1-2">(1) Effects Not Related to S and N Deposition</FP> <FP SOURCE="FP1-2">(2) Evidence of Ecosystem Effects of S and N Deposition</FP> <FP SOURCE="FP1-2"> (3) Sulfur Deposition and SO <E T="52">X</E> </FP> <FP SOURCE="FP1-2">(4) Nitrogen Deposition and N Oxides and PM</FP> <FP SOURCE="FP1-2">b. CASAC Advice</FP> <FP SOURCE="FP1-2">c. Administrator's Proposed Conclusions</FP> <FP SOURCE="FP1-2">2. Comments on the Proposed Decision</FP> <FP SOURCE="FP1-2">a. Sulfur Oxides</FP> <FP SOURCE="FP1-2">(1) Comments Regarding Adequacy of the Existing Standard</FP> <FP SOURCE="FP1-2">(2) Comments in Support of Proposed Adoption of a New Annual Standard</FP> <FP SOURCE="FP1-2">(3) Comments in Disagreement With Proposed Adoption of a New Annual Standard</FP> <FP SOURCE="FP1-2">(4) Comments Regarding Retaining the Existing Secondary Standard</FP> <FP SOURCE="FP1-2">b. Nitrogen Oxides and Particulate Matter</FP> <FP SOURCE="FP1-2">(1) Comments in Support of Proposed Decisions</FP> <FP SOURCE="FP1-2">(2) Comments in Disagreement With Proposed Decisions</FP> <FP SOURCE="FP1-2">3. Administrator's Conclusions</FP> <FP SOURCE="FP1-2">C. Decision on the Secondary Standards</FP> <FP SOURCE="FP-2"> III. Interpretation of the Secondary SO <E T="52">2</E> NAAQS </FP> <FP SOURCE="FP1-2">A. Background</FP> <FP SOURCE="FP1-2"> B. Interpretation of the Secondary SO <E T="52">2</E> Standard </FP> <FP SOURCE="FP-2"> IV. Ambient Air Monitoring Network for SO <E T="52">2</E> </FP> <FP SOURCE="FP1-2">A. Public Comments</FP> <FP SOURCE="FP1-2">B. Conclusion on the Monitoring Network</FP> <FP SOURCE="FP-2"> V. Clean Air Act Implementation Considerations for the Revised Secondary SO <E T="52">2</E> Standard </FP> <FP SOURCE="FP1-2">A. Designation of Areas</FP> <FP SOURCE="FP1-2">B. Section 110(a)(1) and (2) Infrastructure SIP Requirements</FP> <FP SOURCE="FP1-2"> C. Prevention of Significant Deterioration and Nonattainment New Source Review Programs for the Revised Secondary SO <E T="52">2</E> Standard </FP> <FP SOURCE="FP1-2">D. Transportation Conformity Program</FP> <FP SOURCE="FP1-2">E. General Conformity Program</FP> <FP SOURCE="FP-2">VI. Statutory and Executive Order Reviews</FP> <FP SOURCE="FP1-2">A. Executive Order 12866: Regulatory Planning and Review and Executive Order 14094: Modernizing Regulatory Review</FP> <FP SOURCE="FP1-2">B. Paperwork Reduction Act (PRA)</FP> <FP SOURCE="FP1-2">C. Regulatory Flexibility Act (RFA)</FP> <FP SOURCE="FP1-2">D. Unfunded Mandates Reform Act (UMRA)</FP> <FP SOURCE="FP1-2">E. Executive Order 13132: Federalism</FP> <FP SOURCE="FP1-2">F. Executive Order 13175: Consultation and Coordination With Indian Tribal Governments</FP> <FP SOURCE="FP1-2">G. Executive Order 13045: Protection of Children From Environmental Health Risks and Safety Risks</FP> <FP SOURCE="FP1-2">H. Executive Order 13211: Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution or Use</FP> <FP SOURCE="FP1-2">I. National Technology Transfer and Advancement Act (NTTAA)</FP> <FP SOURCE="FP1-2">J. Executive Order 12898: Federal Actions To Address Environmental Justice in Minority Populations and Low-Income Populations and Executive Order 14096: Revitalizing Our Nation's Commitment to Environmental Justice for All</FP> <FP SOURCE="FP1-2">K. Congressional Review Act (CRA)</FP> <FP SOURCE="FP1-2">L. Judicial Review</FP> <FP SOURCE="FP-2">VII. References</FP> </EXTRACT> <HD SOURCE="HD1">Executive Summary</HD> This document presents the Administrator's final decisions in the current review of the secondary NAAQS for SO <E T="52">X</E> , N oxides, and PM. Specifically, this document summarizes the background and rationale for the Administrator's final decisions to revise the secondary SO <E T="52">2</E> standard to an annual average, averaged over three consecutive years, with a level of 10 ppb, and to retain the existing standards for N oxides and PM. In conducting this review of the secondary SO <E T="52">X</E> , N oxides, and PM NAAQS, the EPA has carefully evaluated the currently available scientific literature on the ecological effects of SO <E T="52">X</E> , N oxides, and PM  <SU>1</SU> <FTREF/> as described in the Integrated Science Assessment (ISA) and conducted quantitative air quality, deposition, and risk analyses. The Administrator's final decisions are based on his consideration of the characterization of the available scientific evidence in the ISA; quantitative and policy analyses presented in the Policy Assessment (PA), and related analyses; advice from the Clean Air Scientific Advisory Committee (CASAC); and public comments on the proposed decision. <FTNT> <SU>1</SU>  Welfare effects of PM considered in the review of the PM secondary standards completed in 2020, and reconsidered more recently, include effects on visibility and climate and materials damage (88 FR 5558, Ja ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 769k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━