- What Are Air Toxics?
- Why Monitor For Air Toxics?
- Where Do We Monitor?
- What Do We Compare Monitored Data To?
- Air Monitoring Comparison Values (AMCVs) used in the review of ambient air monitoring data
- Types of Air Toxics Monitoring Networks
What Are Air Toxics?
Air toxics, also known as hazardous air pollutants, are pollutants that are known or suspected to cause cancer or other serious health effects. Benzene, arsenic, and mercury are examples of air toxics.
Each state is responsible for developing and implementing plans to help reduce national air-toxics emissions. In Texas, the TCEQ is responsible. Criteria pollutants such as ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide, particulate matter, and lead are regulated under other federal standards.
Why Monitor for Air Toxics?
Data from monitoring air toxics can be used for finding pollution sources, evaluating air-permit applications, and identifying potential health concerns.
The TCEQ toxicology staff uses ambient air monitoring to assess the potential for measured concentrations of air toxics to impair health and cause odors.
Where Do We Monitor?
The TCEQ measures air toxics concentrations at approximately 102 monitoring sites across Texas, mostly in urban and industrial areas. The 1990 Clean Air Act as subsequently amended identifies 187 toxics; the TCEQ analyzes for 146 of those.
A summary of monitoring sites and the parameters monitored at each site can be obtained by clicking on a region below.
What Do We Compare Monitored Data To?
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.
Types of Air Toxics Monitoring Networks
Community Air Toxics Monitoring Network
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 Chromatograph Network
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.