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About the Air Pollutant Watch List

The Air Pollutant Watch List alerts technical personnel to cities and counties within the state that have areas with elevated concentrations of air pollutants.

New TopicBenzene and the Galena Park, Harris County, TX area have been successfully removed from the APWL!

General Information

What is the Air Pollutant Watch List?

Each year the TCEQ collects an extensive amount of ambient air monitoring data and evaluates the potential for adverse short- and long-term health effects and odors. The Air Pollutant Watch List (APWL) is the TCEQ's program to address areas in Texas where monitoring data show persistent, elevated concentrations of air toxics. The TCEQ uses the APWL process to focus its resources, notify the public, engage stakeholders, and develop strategic actions to reduce emissions. One of the primary strategies for addressing APWL areas includes additional scrutiny for air permit applications that include a request to increase an APWL contaminant. The TCEQ will work with sources to encourage efforts to reduce emissions, may provide assistance to small businesses and local governments to identify strategies for reducing APWL contaminants, may increase monitoring for an APWL area, and may conduct focused investigations for companies located in an APWL area. The following diagram illustrates how the TCEQ uses the air permitting program, ambient air monitoring, and the APWL to ensure that ambient air toxic concentrations are at levels that are protective of public health and welfare.

Diagram that illustrates how the TCEQ uses the air permitting program, ambient air monitoring, and the APWL to ensure that ambient air toxic concentrations are at levels that are protective of public health and welfare.

The framework for the APWL program is outlined in the APWL protocol, which describes the process that the TCEQ will follow for all APWL issues, such as listing, remediating, and delisting APWL areas. The TCEQ may propose to remove an APWL area if ambient monitoring data shows a downward trend, information demonstrates that the improvement will be sustained, and the TCEQ determines that there is no longer a potential for adverse health effects. The TCEQ accepts public comments on all additions to and removals from the APWL.

APWL Resources

What Air Pollutants are Monitored?

Texas monitors and evaluates ambient concentrations of air toxics, which are pollutants known or suspected to cause cancer or other serious health effects. The TCEQ obtains data on approximately 150 air toxics from stationary monitors and also from the deployment of mobile monitoring projects. The TCEQ monitors for volatile organic compounds (such as benzene), carbonyls (such as formaldehyde), polycyclic aromatic hydrocarbons (such as naphthalene), and metals (such as nickel).

Use the Air Monitoring Site Information Table or Air Monitoring Site Information Map to see the location of monitors in a particular area.

How is Ambient Monitoring Data Evaluated?

The TCEQ established ambient state regulatory standards for two air toxics--sulfur dioxide and hydrogen sulfide. For all other monitored air toxics, the TCEQ's Toxicology Division establishes pollutant-specific air quality guideline levels known as Air Monitoring Comparison Values (AMCVs) to protect human health and welfare. The TCEQ establishes APWL areas where ambient monitoring indicates persistent concentrations above state standards or AMCVs.

The U.S. Environmental Protection Agency also established ambient air quality standards for criteria pollutants. These standards are known as the National Ambient Air Quality Standards, or NAAQS, and each state must develop a State Implementation Plan, or SIP, to demonstrate how it will comply with and attain the NAAQS. The Texas SIP is the mechanism that the TCEQ uses for regulating criteria pollutants; the APWL is the mechanism that the TCEQ uses to reduce air toxic emissions and ensure that ambient concentrations of air toxics are below levels of concern.

What Level of Air Permit Review is Required?

The Modeling and Effects Review Applicability Technical Guidance Package (July 2009) Adobe Acrobat PDF Document provides more information about the level of modeling and health effects evaluation that may be required for New Source Review (NSR) permitting. In addition, the TCEQ is providing guidance to companies to better prepare applications for NSR permits and permits by rule. The purpose of the guidance is to increase transparency in the APWL process and to encourage companies to work with the TCEQ to address APWL concerns up front. The guidance does not replace the health effects evaluation of an NSR permit review, which may result in additional permit requirements or restrictions as determined on a case-by-case basis. The TCEQ encourages companies to schedule pre-application meetings to discuss projects that include an increase in an APWL contaminant and is also providing a checklist to help companies prepare for a pre-application meeting.

Air Permit Guidance: Adobe Acrobat PDF Document or Microsoft Word Document

Pre-application Meeting Checklist: Adobe Acrobat PDF Document or Microsoft Word Document

How to Get Involved

Recommend an Area be Added to or Removed from the APWL

You may recommend that specific pollutants and locations be evaluated for addition to or removal from the APWL by sending an email to the APWL Coordinator at Requests should include a description of the location, the pollutant of concern, any supporting information, and your contact information. The TCEQ carefully investigates every recommendation, and you may view past recommendations for addition to (or removal from) the APWL that were not adopted.

For assistance regarding environmental complaints, visit the TCEQ Complaints Reporting Web site.

Contact the TCEQ About the APWL

For further information, contact TCEQ's APWL Coordinator, Jessica Myers, Ph.D., toll-free at 1-877-992-8370 or local at (512)239-1795 or via email at

Sign Up to Receive APWL Announcements

To receive free updates by email regarding the APWL, visit the TCEQ GovDelivery Exit the TCEQ Web site and check the box for Air Pollutant Watch List under the Air Quality heading.

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