Air Pollution Control Program

National Ambient Air Quality Standard Area Boundary Designations

The Clean Air Act requires EPA to review the National Ambient Air Quality Standards, or NAAQS, for each criteria pollutant every five years.  There are six different criteria pollutants including particulate matter (which includes both coarse particles, or PM10, and fine particles, or PM2.5); sulfur dioxide, or SO2; carbon monoxide, or CO; ground-level ozone, or O3; Nitrogen Dioxide, or NO2; and Lead. 

If EPA revises the NAAQS for any criteria pollutant after one of these five year reviews, then EPA is required to establish boundary designations for all areas of the country.  Per the Clean Air Act, States are allowed to submit boundary designation recommendations to EPA for consideration in the final boundary designation.  States must submit their recommendations to EPA within one year after a new NAAQS is finalized.  EPA then reviews the States’ recommendations and issues a 120 day letter to each state informing the State whether EPA is planning to accept the State recommendation or if they plan to modify the State recommendation.  States then have 120 days to respond to these letters in order to offer additional data, justification, and reasoning for EPA to consider prior to the final boundary designations. 

After that, EPA finalizes the boundary designations for each area in the country into one of three categories.  An attainment designation signifies that the air quality in an area is in compliance with the NAAQS.  A nonattainment designation signifies that either the air quality in an area exceeds the level of the NAAQS or that the emissions in the area contribute to a nearby area that is exceeding the level of the NAAQS.  An unclassifiable designation signifies that insufficient data exists to make a determination as to whether an area is attaining or not attaining the NAAQS.  Clean Air Act requirements for attainment and unclassifiable areas are identical, and therefore, often times EPA either designates an area as nonattainment or attainment/unclassifiable.

EPA usually releases boundary designation guidance following the finalization of a NAAQS that includes certain criteria to be considered in the boundary designation process.  The State then uses this guidance in developing their recommendations to EPA.  Below is a list of the boundary designation recommendations, EPA responses to those recommendations, and the finalized area boundary designations for several NAAQS, which EPA has revised in recent years.

Ozone | Sulfur Dioxide | Particulate Matter | Lead
Nitrogen Dioxide
| Carbon Monoxide

All Documents linked below are PDF format unless otherwise noted.

Ozone

Additional information about the Ozone Boundary Designation Process can be found on EPA’s website.

2008 Ground-Level Ozone NAAQS (8-hour standard: 75 parts per billion (ppb))

Revised 2008 8-Hour Ozone Boundary Recommendation (Submitted December 2011)
Revised Ozone Boundary Recommendation Submittal to EPA

EPA 120 Day Letter for the 2008 8-hour Ozone Boundary Designations (Received December 2011)
EPA 120 Day Letter
Attachment to EPA 120 Day Letter

Final Boundary Designations for the 2008 Ground-level Ozone NAAQS
Federal Register Notice (May 21, 2012)

Original 2008 8-Hour Ozone Boundary Recommendation (Submitted March 2009)
Ozone Boundary Recommendation Letter to the U.S. Environmental Protection Agency

Technical Support Documents and Other Attachments for the Original 2008 8-Hour Ozone Boundary Recommendation.

Missouri Summary of Area Ozone Recommendations

St. Louis Area and Southeast Missouri Area Recommendations

Kansas City Ozone Recommendation

Springfield and Southwest Missouri Ozone Recommendation

Appendix A - Meteorological Analysis

Appendix B - Responses to Comments on the Ozone Boundary Recommendation

Appendix C - Written Comments Received on the Proposed Ozone Boundary Recommendation

 

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1997 Ground-level Ozone NAAQS (8-hour standard: 80 ppb)

1997 8-Hour Ozone Boundary Recommendation (Submitted July 2003).
Technical Support Documents for Determination of Nonattainment Boundaries in Missouri for the 1997
8-Hour Ozone National Ambient Air Quality Standard.  This Document has been split into seven parts to speed download time.

EPA 120-Day Letter for the 1997 8-hour Ozone Boundary Designations (Received December 2003)
EPA 120-Day Letter

State Response to EPA 120-Day Letter for the 1997 8-hour Ozone Boundary Designations (Submitted February 2004)
State Response

Final Boundary Designations for the 1997 Ground-level Ozone NAAQS (April 2004)
Preamble to the Final Boundary Designations under the 1997 Ozone NAAQS
List of Areas and the Final Boundary Designations under the 1997 Ozone NAAQS

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Sulfur Dioxide, or SO2

Additional information about the SO2 Boundary Designation Process can be found on EPA’s website. 

2010 Sulfur Dioxide NAAQS (1-hour Standard: 75 parts per billion (ppb))

2010 Revised 1-Hour Sulfur Dioxide Boundary Recommendation (Submitted April 2013)

2010 Original 1-Hour Sulfur Dioxide Boundary Recommendation (Submitted May 2011)

EPA 120-Day Letter for the 2010 SO2 Boundary Designations (Received February 2013)
EPA 120-Day Letter
Attachment to EPA 120-Day Letter

The State is currently reviewing the EPA 120-day letter for the 2010 SO2 boundary designations to determine the appropriate State Response.  Final Designations for the 2010 SO2 NAAQS are expected to be promulgated in summer 2013.

 

Particulate Matter, or PM

Additional information about the PM Boundary Designation Process is available on EPA’s website.

2012 PM NAAQS (Annual Standard for PM2.5: 12 micrograms/cubic meter (µg/m3))

2012 PM2.5 Boundary Recommendations (Submitted December 2013)

2006 PM NAAQS (24-hour Standard for PM2.5: 35 µg/m3)

2006 PM2.5 Boundary Recommendation (Submitted December 2007)
Technical Support Documents for Designation of Areas in Missouri for the PM 2.5 24-Hour National Ambient Air Quality Standard.  This Document has been split into three parts to speed downloading time.

EPA 120-Day Letter for the 2006 PM2.5 Boundary Designations (Received August 2008)
U.S. Environmental Protection Agency Response to Recommendation

State Response to EPA 120-Day Letter for the 2006 PM2.5 Boundary Designations (Submitted October 2008)
Department Response to the U.S. Environmental Protection Agency

Final Boundary Designations for the 2006 PM2.5 NAAQS
Federal Register Notice (Nov. 13, 2009)

1997 PM NAAQS (Annual Standard for PM2.5: 15 µg/m3)

1997 PM2.5 Boundary Recommendation (Submitted March 2004)
1997 PM2.5 Boundary Recommendations and Technical Support Document

EPA 120-Day Letter for the 1997 PM2.5 Boundary Designations (Received June 2004)
EPA 120-Day Letter

Final Boundary Designations for the 1997 PM2.5 NAAQS
Federal Register Notice (Jan. 5, 2005)

Lead

Additional information about the Lead Boundary Designation Process can be found on EPA’s website.

2008 Lead NAAQS (3-month Rolling Standard: 0.15 µg/m3)

2008 Lead Boundary Recommendation (Submitted December 2009)
Lead Designation and Boundary Recommendation. 1.74 MB
Technical Support Document. 3.86 MB

EPA 120-Day Letter for the 2008 Lead Boundary Designations (Received June 2010)
EPA 120-Day Letter (1st round)
Attachment to EPA 120 Day Letter (1st round)

Due to new monitoring requirements under the 2008 Lead NAAQS, EPA had two rounds of designations when this NAAQS was revised.  The boundary designations for the second round in Missouri did not change from the first round.  The EPA letter for this second round of designations can be found below:
EPA 120-Day Letter (2nd round) (received June 2011)

Final Boundary Designations for the 2008 Lead NAAQS
Federal Register Notice (November 22, 2011)

Nitrogen Dioxide, or NO2

Additional information about the NO2 Boundary Designation Process can be found on EPA’s website.

2010 NO2 NAAQS (1-hour standard: 100 ppb)

2010 NO2 Boundary Recommendation (Submitted December 2010)
2010 NO2 NAAQS Boundary Recommendation Letter to EPA
Attachment 1
Attachment 2

EPA 120-Day Letter for the 2010 NO2 Boundary Designations (Received June 2011)
EPA 120-Day Letter

State Response to EPA 120-Day Letter for the 2010 NO2 Boundary Designations (August 2011)
State Response

Final Boundary Designations for the 2010 NO2 NAAQS
All areas in the Country were designated attainment/unclassifiable.

 

Carbon Monoxide, or CO

Additional information about the CO NAAQS can be found on EPA’s website.

1971 CO NAAQS (1-hour standard: 35 ppm, 8-hour standard: 9 ppm)
The CO NAAQS were established in 1971.  Although the CO NAAQS have gone through multiple periodic EPA reviews as required by the Clean Air Act, the NAAQS have not been changed since that time.  Therefore, no boundary designation processes for CO have occurred in many years.