Air Pollution from Particulate Matter
- What is particulate matter?
- Latest air quality planning that addresses the PM standard
- Related Web pages and publications
- Get more information on the Texas SIP and contact the TCEQ
What is particulate matter?
Particulate matter, or particulates, are anything that is suspended in the air. Particulates are classified by size. Larger or coarse particles range from 2.5 to 10 microns, while fine particles measure 2.5 microns or smaller. Particulates can be caused by natural phenomena or human activity. In high enough concentrations, particulates can aggravate existing respiratory problems or trigger new ones. The TCEQ measures both fine and coarse particulates across the state of Texas.
Inhalable coarse particulate matter, or PM10, is defined as particles with an aerodynamic diameter less than or equal to a nominal 10 microns. PM10 can be found near roadways or dusty areas.
Fine particulate matter, or PM2.5, is defined as particles with an aerodynamic diameter less than or equal to a nominal 2.5 microns. PM2.5 can be emitted directly, or can form when gas emissions react in the atmosphere. The EPA established annual and 24-hour National Ambient Air Quality Standards (NAAQS) for PM2.5 for the first time in 1997 to address data indicating that these small particles, which can penetrate more deeply into the lungs, may pose greater health risks than larger particles.
Latest air quality planning that addresses the PM standard
Last updated: 5/16/2011
Comments on Proposed Disapproval of 2006 PM2.5 Infrastructure Plan
On May 13, 2011, the Texas Commission on Environmental Quality (TCEQ) submitted comments regarding the United States Environmental Protection Agency's (EPA) proposed disapproval of Texas' state implementation plan (SIP) revision addressing infrastructure requirements for the 2006 PM2.5 NAAQS.
On April 13, 2011, the EPA published in the Federal Register a proposed disapproval of Texas' infrastructure submission ("infrastructure SIP") addressing the Federal Clean Air Act, §110(a)(2)(D)(i)(I) transport requirements for the 2006 PM2.5 NAAQS (76 FR 20602). Texas' 2006 PM2.5 infrastructure SIP revision was submitted to the EPA on November 23, 2009.
Recommendation: Designation for Harris County under the 1997 Annual PM2.5 Standard
On October 8, 2009, the EPA sent a letter 
to the governor concerning violations of the annual PM2.5 standard at the Clinton Drive monitor in Harris County for 2006 through 2008. The EPA’s request was based on 2006–08 ambient air monitoring data that indicated one monitor in Harris County was above the 1997 annual PM2.5 NAAQS of 15 µg/m3. On November 19, 2009, the TCEQ hosted an informational meeting regarding the designation recommendation for Harris County. The meeting provided the public an opportunity for discussion on the recommendation.
On January 20, 2010, the TCEQ sent to the EPA certified, quality-assured 2009 data for the three monitors in Harris County, which all report arithmetic means below 13 µg/m3. On February 5, 2010, the governor recommended to the EPA that all areas in Texas, including Harris County, remain designated in attainment of the 1997 annual PM2.5 standard.
- Recommendation Package:
On April 28, 2010, the EPA sent a letter to the governor of Texas concurring with his recommendation that Harris County remain attainment for PM2.5 based on 2009 design values.
Recommendation: Designation under the 2006 24-hour PM2.5 Standard
On December 18, 2006, the EPA revised the NAAQS for 24-hour PM2.5 from 65 µg/m3 to 35 µg/m3. On December 18, 2007, the governor submitted to the EPA a recommendation that all areas in Texas be designated attainment for the 2006 24-hour PM2.5 standard.
- Recommendation Package:
On December 22, 2008, the EPA confirmed to the governor in writing that all areas in Texas are in attainment of the 24-hour PM2.5 standard.
The EPA recommends that states identify violating areas using the most recent three years of air quality data stored in the EPA Air Quality System (AQS). PM2.5 violations are identified using data from Federal Reference Method and the Federal Equivalent Method monitors sited and operated in accordance with Title 40, Code of Federal Regulations, Part 58. Based on 2004–06 monitoring data from the EPA AQS, no monitors in Texas are violating the 2006 PM2.5 24-hour standard.
One special-purpose microscale monitor in El Paso, the Sun Metro site, has measured PM2.5 levels higher than the 24-hour standard. In 2000, the agency established Sun Metro as a microscale site with a continuous PM2.5 monitor and a supplemental speciation sampler to analyze the impact of transport into Texas across the Rio Grande River. However, the EPA has not included these data in the AQS because the monitor is a microscale monitor. The table submitted as part of the recommendation package explains that the EPA has not previously included Sun Metro as a monitor for designation, and the commission recommends excluding the Sun Metro site from the nonattainment-designation recommendation. All monitors in Texas with data eligible for comparison to the 24-hour PM2.5 standard meet the revised standard.
Related Web pages and publications
- EPA General Page on Particulate Matter
- NAAQS for Particulate Matter
- TCEQ PM2.5 Data: Soot, Dust, Smoke (Particulate Matter)
- Clean Air Interstate Rule
- Complete List of Texas SIP Revisions
