Toxicological Evaluations of Ambient Air Monitoring Data

Types of data available from the various monitoring networks may include:

• Canister samples collected throughout the state's urban and industrial areas are collected every 6th day and analyzed using a gas chromatograph-mass spectrometer.
• Automated Gas Chromatography samplers (AutoGCs) located throughout the greater Houston, Dallas, El Paso, Corpus Christi, and Odessa areas monitor for VOCs. One 40-minute sample is collected each hour and analyzed automatically on-site.
• Carbonyl samples from the Houston, Dallas-Ft. Worth, and El Paso areas are collected every 6th day and analyzed for carbonyl compounds using high-performance liquid chromatography.
• As part of an U.S. Environmental Protection Agency border grant, the TCEQ monitors polyaromatic hydrocarbon (PAH) concentrations in air at sites along the Texas-Mexico border. Samples are collected every 6th day and analyzed for PAH compounds using a gas chromatograph-mass spectrometer.
• TSP, PM10 and PM2.5 filter samplers monitor for air toxics-metals. Twenty-four-hour samples are collected every sixth or third day.

For evaluation of ambient air monitoring results, acute and chronic inhalation reference values and inhalation unit risk factors are used to assess the potential for exposure to the measured concentrations to impair human health.

To assess potential welfare effects for monitoring results, the TCEQ toxicology staff uses odor- and vegetation-based ESLs.

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