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Air Pollution from Particulate Matter

General information on particulate matter (PM), and TCEQ planning that addresses the PM National Ambient Air Quality Standards (NAAQS).

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Particulate Matter (PM): The Facts

What is PM?

Particulate matter (PM) is a mix of small particles and liquid droplets. These particles can be made up of acids, organic chemicals, metal, dust, or soil. Particulates are different in several ways including size. Federal definitions for PM based on particle size can be found in 40 CFR §58.1 .

PM10 is sometimes referred to as coarse particles. They consist of particles that are less than or equal to 10 micrometers in diameter.

PM2.5 are fine particles and are the smallest particles that are regulated. They consist of particles that are less than or equal to 2.5 micrometers in diameter. By comparison, the average diameter of human hair is 70 micrometers.

The federal Clean Air Act (FCAA) requires the United States Environmental Protection Agency (EPA) to set air quality standards, including those for PM, to protect both public health and the public welfare (e.g., visibility, crops, and vegetation).

What are the health effects of PM?

Particle size is directly related to its potential for causing health problems. Small particles less than 2.5 micrometers in diameter can be inhaled deeper into the lungs. Scientific studies have linked exposure to high concentrations of some types of PM with a variety of problems, including:

  • irregular heartbeat;
  • aggravated asthma;
  • decreased lung function;
  • increased respiratory symptoms, such as irritation of the airways, coughing or difficulty breathing;
  • nonfatal heart attacks; and
  • premature death in people with heart or lung disease.

These associations are much less certain at concentrations below the current standard set by the EPA for PM in ambient air.

How does PM affect the environment?

PM can contribute to haze, which reduces visibility. When PM is present in the air, it can absorb sunlight, and it can reflect sunlight. This reduces clarity in the air and can cause haze. Humid air can also combine with PM to further reduce visibility. PM from the air can deposit on water and soil harming ecosystems, soil, and crops. PM can stain and damage stone and other materials, including culturally important objects such as statues and monuments.

Where can I see daily PM levels in my area?

The TCEQ has multiple monitors that directly measure PM concentrations throughout the state. The TCEQ also offers air quality forecasts that include PM. The public can sign up for these to be delivered via e-mail using the Agency’s GovDelivery system.

The EPA provides a website that monitors and forecasts the quality of the air using a scale called the Air Quality Index (AQI). The AQI is based on the National Ambient Air Quality Standards (NAAQS) for the six criteria pollutants. The AQI is on a scale of 0 to 500, with 100 corresponding to the NAAQS set by the EPA. A higher AQI value means a larger level of air pollution and a greater potential health concern. These forecasts can be found on the EPA’s Air Now website.

You can also sign up to receive e-mail alerts about PM through the EPA’s EnviroFlash website.

How can I protect myself from PM?

Although healthy individuals are unlikely to be affected by the low levels of particles present in ambient air, some especially sensitive individuals (such as those with severe asthma) may wish to avoid excess exposure. Your chances of being affected by particles increase the more strenuous your activity and the longer you are active outdoors. You should also avoid standing in front of smoke from any fire. If your activity involves prolonged or heavy exertion, reduce your activity time or substitute another that involves less exertion. Go for a walk instead of a jog, for example. Plan outdoor activities for days when particle levels are lower. The highest levels of particulate matter is generally near roadways, so you should avoid exercising in those areas.

What can I do to reduce PM?

There are several things that you can do to reduce PM in your area. Below are some tips you can follow including:

  • conserve electricity; consider setting your thermostat a little higher in the summer and lower in winter;
  • participate in local energy conservation programs;
  • keep car, boat, and other engines properly tuned, and avoid engines that smoke; avoid or slow your vehicle speed on dirt and unpaved roads;
  • car pool, use public transportation, bike, or walk when possible;
  • combine errands to reduce "cold starts" of your car and avoid extended idling;
  • consider using gas logs instead of wood in your fire place or burn only dry, seasoned wood; and
  • mulch or compost leaves and yard waste instead of burning.

What is being done about PM?

The EPA reviews the health-based standard for PM and following those reviews may change the standard. In December 2012, the EPA lowered the primary annual PM2.5 National Ambient Air Quality Standard for fine particles to 12.0 micrograms per cubic meter. The agency retained the existing standards for PM10.

All areas of Texas are designated as attainment for the fine particulate standard. Improvements in air quality for particulate pollution have been achieved by TCEQ regulatory and voluntary efforts in cooperation with local governments, industry, and citizens. El Paso is currently designated as nonattainment for PM10.

The state submitted designation recommendations to the EPA for the 2012 PM2.5 standard on November 26, 2013. On January 15, 2015, the EPA published final designations in the Federal Register, designating all areas of Texas unclassifiable/attainment. For more information see the Latest Air Quality Planning that Addresses the PM NAAQS

What about indoor air quality?

The EPA has identified and characterized significant risks to public health from indoor environmental contaminants that are commonly found in homes, schools, offices, and other buildings where most Americans spend up to 90% of their time. Indoor levels of air pollution may be up to two to five times higher, and occasionally 100 times higher, than outdoor levels. Common indoor air contaminants include radon, tobacco smoke, mold, irritant and allergenic asthma triggers, combustion by-products and VOCs. Indoor contaminants may be of natural origin (e.g., radon, allergens, and molds), may derive from products used indoors (e.g., finishes, furnishings, and cleaning products) and may result from indoor processes and behaviors (e.g., smoking, use of unvented combustion sources; or cleaning, operation, and maintenance procedures). Building systems (e.g., heating, ventilating, and air conditioning) also have a direct influence on the type and amount of exposure building occupants may experience from environmental contaminants indoors. For more information on indoor air quality visit the EPA's Indoor Air Quality webpage.

What should I consider in weighing the EPA’s recommendations to limit exercise and stay indoors because of particulate matter concentrations?

The World Health Organization ranks physical inactivity as a major risk factor for heart disease, breast cancer, colon cancer, and diabetes. Recently, it has been estimated that over 30% of the U.S. population is fully inactive. For children, the risks of obesity are well-documented Given that physical exercise is important  for adults and children for reasons including prevention of disease and obesity, individuals must consider those benefits when making choices about following the EPA’s recommendations to limit exercise outdoors and stay indoors because of concentrations of PM in ambient air. A personal decision to limit outdoor activities should consider weather conditions more than particulate matter levels. Exercise performance is compromised in the heat, and temperature should be considered when making personal choices about exercising.

What is the Air Quality Index and how can I sign up to receive e-mail alerts and alerts on mobile devices?

The EPA has provided a scale called the AQI for rating air quality. The AQI scale is based on the NAAQS and is described in the Code of Federal Regulations, Part 58, Appendix G. Each NAAQS pollutant has a separate AQI scale, with an AQI rating of 100 corresponding to the concentration of the federal standard for that pollutant. Additional information about the AQI and how it can be used is available from the EPA's AQI Basics  webpage.

You can sign up to receive e-mail alerts through the EPA’s EnviroFlash website.  

Latest air quality planning that addresses the PM NAAQS

Last updated: 5/19/2023

Public Information Meetings – Proposed Particulate Matter NAAQS Revision

The TCEQ hosted virtual public information meetings to provide information on the potential impacts of the EPA's proposal to lower the primary annual PM2.5 NAAQS from its current level of 12 µg/m3 to between 9 and 10 µg/m3.

The TCEQ provided information on the proposed NAAQS revision, designations process, and requirements for an area designated nonattainment. These meetings focused on implementation of the potential revised NAAQS and not on the health effects associated with the NAAQS revision. The virtual public information meetings were held for potentially impacted counties on the following days:

Information on the PM2.5 NAAQS proposal is available on the EPA's website.

Infrastructure and Transport SIP Revision for the 2012 Primary Annual PM2.5 NAAQS

On November 4, 2015, the commission adopted the FCAA, Section 110(a)(1) and (2) Infrastructure and Transport State Implementation Plan (SIP) Revision for the 2012 primary annual PM2.5 NAAQS (Project No. 2014-029-SIP-NR). The SIP revision outlines the requirements of FCAA, Section 110(a)(2)(A) through (M), and the Texas provisions supporting the requirements for the 2012 PM2.5 NAAQS. These requirements include basic program elements such as enforceable emission limitations and control measures, air quality monitoring and modeling, a permitting program, adequate funding and personnel, authority under state law to carry out the plan, emissions reporting, emergency powers, public participation, and fee collection. This revision also includes a technical demonstration to support the determination that Texas meets the interstate transport requirements of Section 110(a)(2)(D)(i)(I).

Final Designations for the 2012 Primary Annual PM2.5 NAAQS

On January 15, 2015, the EPA published in the Federal Register final designations for the 2012 primary annual PM2.5 standard ( 80 FR 2206 ). The EPA designated all areas of Texas unclassifiable/attainment.

Commission Approved Recommended Designations for the 2012 Primary Annual PM2.5 NAAQS 

On October 23, 2013, the commission approved the executive director's designation recommendations for the 2012 primary annual PM2.5 NAAQS. The TCEQ recommends that all counties in Texas with applicable PM2.5 monitoring data be designated attainment and all other counties be designated as unclassifiable/attainment. This recommendation is based on the three most recent years of quality-assured air data from the current federal reference monitoring network for the years 2010 through 2012, the demonstration of exceptional event days for exclusion, and historical PM2.5 monitoring trends. The recommended designations were submitted by the governor to the EPA on November 26, 2013. On August 19, 2014, the EPA sent a letter to Texas  in response to the recommended designations.

PM Data: El Paso 2010, 2011, and 2012 Exceptional Events Demonstration

In accordance with federal regulations, the demonstration documents supporting the TCEQ's exceptional event flags for El Paso PM10 and PM2.5 data for 2010, 2011, and 2012 were provided for public review and comment. There were three PM10 and ten PM2.5 proposed exceptional event flags for data collected at various El Paso monitoring sites on ten separate days from 2010 through 2012. All thirteen of the proposed flags were for high wind regional blowing dust events that are described in more detail in the demonstration document

No public comments were received by the TCEQ and the demonstration was forwarded to the EPA for consideration on December 11, 2013. The EPA considers information provided in the demonstration documents and public comments when deciding whether to accept or reject each proposed flag. EPA concurrence on a flag will remove the data from consideration for determinations of compliance with the 24-hour PM10, the 24-hour PM2.5, or the revised primary annual PM2.5 NAAQS.

For more information, please visit the TCEQ's Air Monitoring webpage for PM flags: Particulate Matter Data Proposed Exceptional Event Flag Demonstrations.

Status: On July 7, 2015, the EPA sent a determination to the TCEQ indicating concurrence with all three proposed El Paso PM10 exceptional events that occurred in 2010 and 2011 and eight of the 10 El Paso PM2.5 exceptional events that occurred in 2011 and 2012. The EPA did not concur with the demonstration of the two PM2.5 exceedances that occurred on February 8, 2011.

PM2.5 Data: Houston 2010, 2011, and 2012 Exceptional Events Demonstrations

In accordance with federal regulations, the demonstration documents supporting the TCEQ's exceptional event flags for Houston's Clinton Drive PM2.5 monitoring data for 2010, 2011, and 2012 were posted for the 30-day public review and comment periods. The exceptional event flags are for: June 9, 10, and July 13, 2010; May 20, 2011; and July 2, 27, and 28, 2012. All three of the 2010 flags are for African dust events. The 2011 flag is for a Mexican and Central American smoke event, and all three of the flags in 2012 are for African dust events. These events are described in more detail in the demonstration documents.

The public comments received by the TCEQ were forwarded to the EPA for consideration. The EPA considers information provided in these demonstration documents and public comments when deciding whether to accept or reject each proposed flag. EPA concurrence on a flag would remove the data from consideration for determinations of compliance with the revised primary annual PM2.5 NAAQS for the period of 2010 through 2012.

For more information, please visit the TCEQ's Air Monitoring webpage for PM flags: Particulate Matter Data Proposed Exceptional Event Flag Demonstrations.

Status: In a March 27, 2014 letter to the TCEQ, the EPA concurred with the TCEQ’s exceptional events demonstration regarding exceedances of the PM2.5 NAAQS that occurred at the Houston Clinton Drive monitoring site in 2010. The EPA excluded flagged 2010 PM2.5 data from consideration in determining Harris County’s attainment status under the primary annual PM2.5 NAAQS.

Public Information Meetings in Houston and El Paso Regarding Area Designations under the 2012 PM2.5 NAAQS

The TCEQ held public information meetings regarding area designations under the 2012 primary annual PM2.5 NAAQS in Houston on July 22, 2013 and in El Paso on September 17, 2013. TCEQ staff presented an overview of the 2012 PM2.5 NAAQS, current monitoring data for the State of Texas, exceptional events, and the process for state designation recommendations to the EPA.

2012 Revised Primary Annual PM2.5 NAAQS

On December 14, 2012, the EPA promulgated a revised rule for the PM NAAQS. In this rule, the EPA strengthened the primary annual PM2.5 standard from 15.0 micrograms per cubic meter (μg/m3) to 12.0 μg/m3. All other existing primary and secondary standards for both PM2.5 and PM10 were retained.

No counties in Texas are currently designated nonattainment nor are any counties in maintenance status for the primary annual PM2.5 standard.

State designation recommendations to the EPA based on 2010 through 2012 data were due December 13, 2013. The EPA's final designations were expected by December 12, 2014. The near-road monitoring schedule requires monitors in Dallas-Fort Worth and Houston-Galveston-Brazoria areas to be operational on January 1, 2015 with monitors in Austin-Round Rock and San Antonio areas to be operational on January 1, 2017.

For additional information, please visit the EPA's Particulate Matter Pollution webpage.

Comments on Proposed Disapproval of 2006 PM2.5 Infrastructure Plan

On May 13, 2011, the TCEQ submitted comments regarding the EPA's proposed disapproval of Texas' 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 FCAA, §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 through 2008 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.

On April 28, 2010, the EPA sent a letter to the governor of Texas concurring with his recommendation that Harris County remain attainment for the 1997 annual PM2.5 standard based on 2009 design values.

Related webpages and publications

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