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If you can't always see it, taste it, or maybe even smell it, how do you know air pollution is there? Texas's
extensive air monitoring network strives to answer that question by measuring concentrations of both criteria and toxic ambient air pollutants. The TCEQ, six local governmental entities, four
private organizations, and even the federal government operate over 140 permanent monitoring sites located across the state that measure pollutants.* Most of these stations monitor criteria pollutants like ozone, sulfur dioxide, and particulate matter, although many also monitor toxics, such as VOCs. Despite this extensive network, many environmental groups believe that more resources should be devoted to monitoring.
Criteria Pollutants. Two types of pollutants -- ozone and respirable particulate matter -- get the most
attention. In 1995 the then-TNRCC, local governments, and private networks monitored ozone seven days a week, 24 hours a day at 51 sites in Texas.* Particulate matter of 10 microns or less was monitored at 45 sites in Texas during 2001, with most sites taking 24-hour averages every sixth day*. After new standards for fine particulate matter were approved in 1997, the TCEQ began installing monitoring for PM 2.5. According to the
EPA, there were over 72 sites in 2002 that monitored for PM 2.5 throughout the state.
Toxics. In 1995 the TNRCC operated 23 monitoring sites in 15 counties that measured 69 VOCs as part of the Community Air Toxics Monitoring Network Sites.* While the TNRCC had plans to expand the network from 23 to a total of 50 sites, budget cuts have not allowed the agency to do so, although by 1997 a total of 35 sites were monitoring toxics.* By 1998, however, the total monitoring network had been expanded to 44 monitoring sites in 18 counties, or close to the original goal of the program. According to an EPA database, in 2001, over 60 monitors were measuring ambient concentrations of benzene (U.S. EPA, AIRData, Query run on October 2003). Air toxics selected for monitoring were those emitted in the largest quantities from multiple sources. Some monitoring methods, however, collect average samples of toxics, and thus higher peak concentrations would not be quantified, although the peak concentrations do influence the average itself.* In addition, most of the toxics monitoring sites measured 24-hour air samples every sixth day.* Limited ambient air toxics monitoring by the TCEQ has not identified these toxic emissions as a significant public health risk in any particular area, although high levels have been observed along the Gulf Coast of benzene and 1,3- butadiene, caused both by industry and mobile source emissions.*
Mobile Monitoring. The TNRCC has operated a mobile monitoring system since 1971 to help pinpoint local
trouble spots. Recently, the TNRCC expanded its use of mobile monitoring equipment, which includes a self-contained 40-foot mobile laboratory, 7 sampling vans (8 by 8 by 14 feet), and an
air-toxics response trailer.* These vans have equipment for monitoring criteria air pollutants, 75 VOCs, polynuclear aromatic compounds, metals, and even take soil samples.* Examples of recent studies performed by the mobile monitoring system include two mobile laboratory trips in 1993 and 1994 to Brownsville to measure air toxics and to Corpus Christi to study oil refineries.*
Despite the presence of these monitors in the major metropolitan areas, federal requirements and citizen
concern about the health effects of air pollution are generating a demand for more and better air-quality monitoring. For example, the TNRCC and the federal government are currently investing
in PM2.5 samplers in all major metropolitan areas in Texas. Concerns along the U.S.-Mexico border have led to major investments in new monitoring sites in Laredo, Mission and Edinburg, while
the Big Bend station run by the National Park Service has added capabilities to measure ozone as well as visibility. A contract with Baylor University also allows the agency to fly
twin-engine airplanes with special equipment over Big Bend and other areas of the state to assess haze.*
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AIR MONITORING TYPES AND SYSTEMS: CAMS, SLAMS, GREEN EGGS AND HAM?
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Continuous Air Monitoring System (CAMS)
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refers to those monitoring sites which are continually monitoring for a variety of
pollutants, including ozone. There are presently about 50 CAMS stations in Texas.
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State and Local Air Monitoring System (SLAMS)
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simply means that a site is operated by either the TNRCC or a local governmental
entity, such as the El Paso County Air Control District, to measure criteria and possibly toxic pollutants.
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National Air Monitoring System (NAMS)
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indicates that the site has been recognized by, or is operated by, the EPA
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Photochemical Air Monitoring Sites (PAMS)
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refers only to sites located in areas that do not meet national standards for ozone
and are installed to examine how the formation of ground-level ozone occurs. These sites monitor both ozone precursors (VOCs and nitrogen dioxide) as well as ozone
itself and meteorological data (wind direction, speed, and temperature). PAMS help local governments and the TCEQ determine how and at what altitude ozone forms
and therefore how best to prevent its formation..* Recently, the TCEQ partnered with industry leaders to add seven new PAMS sites in the Houston-Galveston-Brazoria area. Each of the new monitor will provide measurement data on 56 component VOCs, as well as upon ozone, nitrogen oxides, wind speed, direction, temperature and radiation. The addition of the monitors brings the total number in Houston to ten.
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Source: TNRCC, Information from Monitoring Operations Division, Office of Air Quality, Austin.
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