Particulate matter refers to a mixture of solid particles and liquid droplets found in the air. Some particles are large enough to be seen with the naked eye. Others are so small they can only be detected using an electron microscope.

Particulate matter is divided into two different groups. 

  • PM2.5: Fine particles that are smaller than 2.5 microns in size. Industrial and residential combustion and vehicle exhaust emit fine particles into the air. These activities include burning oil, coal, wood or residential waste. Fine particles also form in the atmosphere when chemical reactions in the air transform gases, such as sulfur dioxide, nitrogen oxides and volatile organic compounds, into microscopic solid or liquid particles. Fine particles can affect the health of everyone but primarily affect children, elderly and individuals with asthma and cardiopulmonary disease.
  • PM10: Coarse particles that are smaller than 10 microns in size. 

Fine Particulate Matter (PM2.5)

On Dec. 14, 2012, EPA revised the National Ambient Air Quality Standard (NAAQS) for PM2.5. The previous standards for PM2.5 were promulgated in 1997 and 2006 and included an annual standard and a 24-hour standard. The annual standard, which was set in 1997, was 15 micrograms per cubic meter (µg/m3), and the 24-hour standard, which was set in 2006, is 35 µg/m3. The revised NAAQS finalized in December 2012 retained the 24-hour standard, but lowered the annual standard from 15 µg/m3 to 12 µg/m3.

2012 Standard

Annual PM2.5 Standard: 12 micrograms/cubic meter or µg/m3

Boundary Recommendations

2012 Standard Boundary Recommendations Actions Table

MoDNR Submittal Date MoDNR Action/Document EPA Date EPA Action/Document
Dec. 10, 2013

2012 PM2.5 Boundary Recommendations

 

Jan. 1, 2015

Final Boundary Designations for the 2012 PM2.5 NAAQS:

[80 FR 2206]
Effective Date: 4/15/2015

Oct. 28, 2014 Department Response to EPA 120-Day Letter for 2012 PM Standard Aug. 19, 2014 EPA 120-Day Letter for the 2012 PM2.5 Standard

Infrastructure SIP

2012 Standard Infrastructure SIP Actions Table

MoDNR Submittal Date MoDNR Action/Document EPA Date EPA Action/Document
Sept. 24, 2015

Infrastructure Elements for the 2012 Annual PM2.5 Standard

Oct. 1, 2018

Approval of Elements 110(a)(2)(D)(i) prongs 1 and 2; 
[83 FR 49299]

Sept. 24, 2018 Approval of Elements 110(a)(2)(D)(i) prong 4; 
[83 FR 48242]
March 22, 2018 Approval of all Elements except 110(a)(2)(D)(i) prongs 1, 2 and 4; 
[83 FR 12496]

St. Louis

2012 Standard St. Louis Actions Table

MoDNR Submittal Date MoDNR Action/Document EPA Date EPA Action/Document
Dec. 10, 2018

St. Louis 2012 PM2.5 Unclassifiable Area Redesignation Request

July 29, 2019

Approval - Redesignation

[84 FR 36742]
Effective Date: 4/15/2015

2006 Standard

24-hour PM2.5 Standard: 35 micrograms per cubic meter, or µg/m3

Boundary Recommendations

2006 Standard Boundary Recommendations Actions Table

MoDNR Submittal Date MoDNR Action/Document EPA Date EPA Action/Document
Dec. 6, 2007

2006 PM2.5 Boundary Recommendation

Nov. 13, 2009

Final Boundary Designations for the 2006 PM2.5 NAAQS:

[74 FR 58688]
Effective Date 12/14/2009

Oct. 2008 Department Response to EPA 120-Day Letter Aug. 18, 2008 EPA 120-Day Letter for the 2006 PM2.5 Standard

Infrastructure

2006 Standard Infrastructure Actions Table

MoDNR Submittal Date MoDNR Action/Document EPA Date EPA Action/Document
Aug. 27, 2009

Infrastructure Elements for the 2006 PM2.5 Standard

June 21, 2013

Approval - 2006 PM2.5 Infrastructure SIP

[78 FR 37457]

1997 Standard

Annual PM2.5 Standard: 15 micrograms per cubic meter, or µg/m3

Boundary Recommendations

1997 Standard Boundary Recommendations Actions Table

MoDNR Submittal Date MoDNR Action/Document EPA Date EPA Action/Document
March 8, 2004

1997 PM2.5 Boundary Recommendations

Jan. 5, 2005

Final Boundary Designations for the 1997 PM2.5 NAAQS

[70 FR 944]
Effective Date 4/5/2005

June 29, 2004 EPA 120-Day Letter for the 1997 PM2.5 Standard

Infrastructure

1997 Standard Infrastructure Actions Table

MoDNR Submittal Date MoDNR Action/Document EPA Date EPA Action/Document
Feb. 1, 2007

Infrastructure Elements for the 1997 PM2.5 Standard

July 22, 2013

Approval of all elements except 110(a)(2)(D)(i) prongs 1-4:
[78 FR 37457]

Oct. 7, 2011 Federal Plan for elements 110(a)(2)(D)(i) prongs 1  and2:
[76 FR 48208]
July 9, 2007 Approval of elements 110(a)(2)(D)(i) prongs 3 and 4:
[72 FR 25975]

St. Louis

1997 Standard St. Louis Actions Table

MoDNR Submittal Date MoDNR Action/Document EPA Date EPA Action/Document
Nov. 12, 2019

Revised - St. Louis 1997 PM2.5 Maintenance Plan

Sept. 30, 2021

Sept. 30, 2021

Approval - Maintenance Plan Revision

[86 FR 54106]
Effective Date 11/01/21

March 27, 2014 Supplement/Revision to Original St. Louis 1997 PM2.5 Maintenance Plan and Redesignation Request Aug. 3, 2018

Approval - Maintenance Redesignation

[83 FR 38033]
Effective Date 10/02/18

Aug. 26, 2011 Original St. Louis 1997 PM2.5 Maintenance Plan and Redesignation Request    

Coarse Particulate Matter (PM10)

EPA established the most current standard for coarse particulate matter (PM10) in 2006. The standard is based on the 24-hour average concentrations set at a level of 150 micrograms per cubic meter, or µg/m3.

2006 Standard

24-hr PM10 Standard: 150 µg/m3

Carthage

2006 Standard Carthage Actions Table

MoDNR Submittal Date MoDNR Action/Document EPA Date EPA Action/Document
May 29, 2014

Americold Logistics 24-hour PM10 Standard Consent Judgment

Jan. 28, 2016

Approval - Consent Judgment

[80 FR 4888]

Related Links

Particulate Matter Pollutants and Sources - Learn more about the weekly and quarterly air quality monitoring data for PM2.5 and PM10 on the department's website.

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