PM2.5 Planning Efforts: Attainment Designations
PM2.5 Planning Efforts
The United States Environmental Protection Agency (EPA) initially promulgated National Ambient Air Quality Standards (NAAQS) to protect public health and welfare from the harmful effects of particulate matter less than 2.5 microns in diameter (PM2.5) on July 16, 1997. Subsequent to establishing the NAAQS, EPA designated PM2.5 nonattainment areas that included Fairfield and New Haven Counties with parts of northern New Jersey and metropolitan New York in a multi-state nonattainment area. The remainder of the state was designated attainment.Planning efforts resulted in monitoring of attainment statewide by 2009. On June 22, 2012, DEEP formally submitted to the EPA a request to redesignate New Haven and Fairfield counties attainment along with the first of two required maintenance plans. The second maintenance plan was proposed on January 11, 2023, and was approved by EPA on November 15, 2024.
On February 7, 2024, EPA promulgated a revision to the annual standard, strengthening it from 12.0 µg/m3 to 9.0 µg/m (effective May 6, 2024). On February 7, 2025, DEEP formally submitted to the EPA a request to designate the entire state attainment.
Ambient PM2.5 concentrations have greatly declined as federal and state air pollution control programs continue to reduce emissions of PM2.5 and its precursors.
Links to relevant documents and correspondence are provided below, in reverse chronological order
Connecticut's Designation for the 2024 PM2.5 Annual NAAQS
- Governor's Letter February 7, 2025 (PDF)
- Technical Support Document (PDF)
- Addendum to TSD (PDF)
Connecticut's Second 10-Year Maintenance Plan for New Haven and Fairfield Counties.
- EPA's Approval of CT's Limited Maintenance Plan (PDF)
- Supplement to Limited Maintenance Plan: Motor Vehicle Assessment February 21, 2024 (PDF)
- Cover Letter May 8, 2023 May 8, 2023 (PDF)
- Final Limited Maintenance Plan (PDF)
- Appendix A: CDV Calculations
- Certification of Public Process (PDF)
- Response to Comments (PDF)
- EPA Comment Letter February 21, 2023 (PDF)
- Notice of Intent (PDF)
- Connecticut's Limited Maintenance Plan (Proposed) January 11, 2023 (PDF)
- Appendix A: CDV Calculations
Connecticut's Infrastructure SIP for the 2012 PM2.5 NAAQS, Submitted December 15, 2015.
- EPA's Proposed Approval March 19, 2018 (Website)
- Cover Letter March 19, 2018 (PDF)
- Enclosure A: Technical Support Document (PDF)
- Attachments A - F (PDF)
- Enclosure B: Notice (PDF)
- Enclosure C: Certification of Public Process (PDF)
- Enclosure D: Comments and Responses (PDF)
- EPA Comment Letter, December 7, 2015 (PDF)
- Connecticut's Designation Recommendation for 2012 PM2.5 NAAQS, December 13, 2013 (PDF)
- EPA Approval of Connecticut's PM2.5 Redesignation Request, Sept 24, 2013 (PDF)
- EPA's "Clean Data" Finding for the 2006 24-Hour PM2.5 NAAQS, December 31, 2012 (PDF)
- EPA PM2.5 Infrastructure SIP Approval, October 16, 2012 (PDF)
- NSR SIP revision meeting PM2.5 Infrastructure SIP Commitments, October 9, 2012 (PDF)
- Additional Update to Connecticut's PM2.5 Infrastructure Submittals, July 11, 2012 (PDF)
- Final PM2.5 Redesignation Request and Maintenance Plan SIP, June 22, 2012
- Update to Connecticut PM2.5 Infrastructure Submittals, June 15, 2012 (PDF)
- Addendum to the CAA §110(a)(2)(D)(i)(I) Portion of Connecticut's Infrastructure Submittal for the 2006 PM25 NAAQS (PDF)
- CTDEP's Request for a "Clean Data" Determination for the 2006 24-hour PM2.5 NAAQS (PDF)
- Request to Withdraw a Portion of Connecticut's PM2.5 Infrastructure Adequacy Determination (PDF)
- EPA's "Clean Data" Finding for the 1997 Annual PM2.5 NAAQS (PDF)
- EPA's 2010 Proposed Transport Rule (PDF)
- EPA's Final Rulemaking (November 13, 2009) Establishing Nonattainment Boundaries for the 2006 24-hour PM2.5 NAAQS (PDF)
- October 8, 2009 Letter re. PM2.5 Designations from EPA to Governor Rell (PDF)
- EPA Guidance (September 25, 2009) on SIP Elements Required Under Sections (a)(1) and (2) for the 2006 24-Hour PM2.5 NAAQS
- Connecticut's Revision to the State Implementation Plan (SIP) for Annual Fine Particulate Matter (PM 2.5) Attainment Demonstration (November 18, 2008)
- CTDEP's September 18, 2009 Letter documenting the adequacy of Connecticut's State Implementation Plan with regard to Clean Air Act Section 110(a)(1) and (2) for the 2006 Fine Particulate Matter National Ambient Air Quality Standard (8 KB, PDF)
- Adequacy Determination for Infrastructure Elements: 1997 NAAQS for Fine Particulate Matter (September 4, 2008, PDF)
- CTDEP's, December 14, 2007 Recommended Designations for the 24-Hour PM2.5 National Ambient Air Quality Standard (2.82 KB, PDF)
- CTDEP's, January 30, 2006 Comments on EPA's Proposed Rule to Implement the Fine Particle National Ambient Air Quality Standards (899 KB, PDF)
- EPA's December 5, 2005 denial to exclude Fairfield and New Haven counties from the CT-NJ-NY PM2.5 non-attainment area (352 KB, PDF)
- Commissioner McCarthy, February 15, 2005 Letter to EPA asking for reconsideration of non-attainment designation (1162 KB, PDF)
- EPA's Final Rulemaking (January 5, 2005) Establishing Attainment and Nonattainment Areas with Respect to the 1997 NAAQS (PDF)
- Governor Rell, December 20, 2004 Letter to EPA Administrator Leavitt (343 KB, PDF)
- EPA's December 17, 2004 Announcement Letter for Connecticut (134 KB, PDF)
- EPA Region I, December 17, 2004 Press Release (230 KB, PDF)
NYDEC submitted comments in October 2004 to EPA concerning the designation process, including several that relate to Connecticut's recommendations to EPA:
In August 2004, CTDEP responded to EPA's draft recommendations regarding attainment designations. EPA acknowledged receipt of CTDEP's response in a September 28, 2004 letter:
- EPA's Correspondence to Governor Rell September 28, 2004 (PDF, 46K)
- Governor's Letter August 30, 2004 (792 KB, PDF)
- CT DEP Rebuttal to EPA's Response August 26, 2004 (4463 KB, PDF)
EPA indicated its intent to modify the CTDEP's original recommendations in a response dated June 29, 2004:
Connecticut's original recommendation for a statewide attainment designation, along with supporting documents, was provided to EPA in February 2004:
- Governor's Letter February 10, 2004 (120 KB, PDF)
- Technical Support Document Recommendation for PM2.5 Designation February, 2004 (corrected August 2004) (227 KB, PDF)
- Figures for Technical Support Document February, 2004 (8773 KB, PDF)
- Appendix - Connecticut DEP PM Monitoring Plan July 1, 1998 (521 KB, PDF)
Content Last Updated on July 24, 2026