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SOURCES OF AIR TOXICS, STATEWIDE AND IN MAJOR URBAN AREAS
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Source: Joint Select Committee on Toxic Air Emissions and Greenhouse Effect, Interim Report of the Joint Select
Committee on Toxic Air Emissions and Greenhouse Effect (June 199), 14.
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Air toxics is a term that describes a broad group of noncriteria pollutants, including National Emission
Standards for Hazardous Air Pollutants (NESHAP), workplace pollutants, state-regulated pollutants, toxic compounds covered by the Toxics Release Inventory
Program, and other toxic pollutants addressed by the federal Clean Air Act. While total emissions of these compounds are small compared to the criteria air
pollutants -- they are usually measured in pounds, not tons -- their potential impact on human health can be great, especially for individuals living near a source of
emissions. When air toxics are brought into the lungs through inhalation, some are readily absorbed into the bloodstream.
Some air toxics can also irritate sensitive tissues in the
eyes, throat, and nose. Some may cause cancer. Others may cause reproductive dysfunctions, birth defects, or nervous system disorders. Some chemicals
-- including mercury, dioxins, and furans, among others -- are placed in a special category and are referred to as "Endocrine Disruptors" because of their ability to
affect the endocrine system, which secretes hormones into the body in humans and animals. Many of these bioaccumulate through the food chain.
The 1986 Superfund Authorization and Renewal Act required businesses to report all releases into the air, water, or
ground of more than 300 toxic chemicals and 20 toxic chemical compounds. Today, nearly 600 chemical compounds
are covered under the Toxics Release Inventory program. In 2001 Texas' manufacturing industries released over 87
million pounds to the atmosphere and led the nation. However, if industries like electric utilities and metal and coal
mining required to report to the Toxics Release Inventory for the first time in 1999 are included, Texas was actually third in total air emission releases, trailing Ohio and North Carolina .*
Industrial toxics emissions are just part of total toxic air emissions. In 1991 the Texas Air Control Board estimated that
these releases accounted for only 18 percent of total toxic air emissions, while mobile sources -- automobiles,
motorcycles, pickups, vans, and trucks -- accounted for 24 percent. On a statewide basis, "area sources" -- dry
cleaners, solvent and paint shops, and wastewater treatment plants, among others -- emit up to three times the amount of toxics that major industries do statewide.* Still, the contribution of total air toxic emissions of each of these
categories -- industrial, mobile, and area sources -- varies widely with location.
The EPA has had the authority to set standards for hazardous air pollutants since 1970. Up until 1993, the list of
national hazardous air pollutant standards stood at seven and included the following chemicals: asbestos, beryllium,
arsenic, mercury, benzene, vinyl chloride, and radionuclides. Under the federal Clean Air Act, the EPA is required to
designate control-technology standards for 174 types of facilities that emit 1 or more of the 188 listed hazardous air
pollutants. While 39 standards were due by November 1994, by September 1998 the EPA had published final rules for only 29 standards, affecting 62 sources.* Since then, many important new emission standards for toxics -- including
mercury, dioxin and furans -- have been developed for sources such as hazardous waste incinerators and cement kilns
that burn hazardous wastes. The EPA has identified 21 pollutants as mobile source air toxics, including diesel
particulate matter and organic gases. Under the Urban Air Toxics Strategy (UATS), EPA has also identified a list of 33
of the 188 compounds that pose potential health impacts in urban areas. Texas state officials believe that 10 of these
compounds -- benzene, 1,3-butadiene, chloroform, acrolein, carbon tetrachloride, formaldehyde, lead, arsenic, cadmium and nickel -- are potential problems in Texas*.
For those compounds not classified as criteria pollutants or not having national hazardous air pollutant standards, air
toxicologists and regulators at the TCEQ have conducted site-specific reviews of predicted or actual impacts for
potential adverse effects. "Effects screening levels" (ambient air concentration guidelines, or ESLs) are used to gauge
the potential of toxic air emissions associated with expansion of an existing facility or construction of a new facility to cause adverse health or welfare effects.* Nevertheless, the use of ESLs as a defacto regulatory standard has been
criticized since many believe actual impacts can be felt at much lower levels.
While Texas keeps an extensive air toxic emission inventory -- how many pounds of toxics are actually emitted in the
air -- there is much less data on levels of toxics in the ambient air. In 1992 the then-TNRCC established the Community Air Toxics Monitoring Program, composed of 15 monitoring sites, a total which has expanded to 44 monitors located in
18 counties.* Similarly, while initially the network only monitored for 18 Volatile Organic Compounds, today it monitors
for some 85 different toxic compounds. Other monitoring efforts are aimed at special projects to sample for hydrogin
sulfide, polycyclic aromatic hydrocarbons (PAHs) and sulfates and a smaller network of monitors looking for 16 carbonyls in Houston, Dallas and El Paso.
Since the toxics monitoring program began, benzene, a human carcinogen, has been the only compound consistently
detected at levels above the effects screening levels. Monitoring locations in Harris, Galveston, Jefferson, and Orange
Counties have all shown high levels of benzene above the ESL. For example, in 1995 benzene concentrations exceeded the 24-hour screening level at 7 sites and the annual screening level at 8 sites.* Overall, however, benzene
concentrations came down at most monitoring sites between 1993 and 1999*.
The TNRCC determined that the benzene measurements that exceeded the 24-hour effects screening levels would not
result in adverse acute health effects. While long-term exposure to benzene at levels significantly greater than the
guidelines annual levels may increase the lifetime risk of developing leukemia or affect the formation of blood, the
TNRCC determined that measured levels of benzene have significantly decreased over the past ten years.* The
commission did, however, note that it was important to prevent benzene levels from increasing and to take efforts to reduce potential public exposure.*
Benzene is a constituent of gasoline; it is released during refueling and is a component of car exhaust. Benzene is also
released during industrial refining processes and from benzene storage tanks. In Texas the counties along the Gulf
Coast have the greatest number of sources of benzene because of the large number of petrochemical companies and petroleum refineries. Air emissions of benzene, as well as other VOCs, like toluene and xylenes, from manufacturing
facilities and ambient air concentrations near industrial sites decreased between 1989 and 1994, as well as between 1994 and 2001.* In addition, monitoring results showed that 1,3-butadiene exceeded its 24-hour effects screening
levels at monitoring sites in Port Neches, Port Arthur, Texas City and Houston in 1999 and 2000. In Port Neches,
industry has worked to reduce emissions of this toxic because of these high levels.* The Texas counties with the
largest point-source emissions of 1,3-butadiene, like those for benzene, are located along the Gulf Coast.*
The state has also initiated special purpose studies at several sites around Texas. For example, after noticing high
levels of arsenic in ambient air analyses in El Paso, the state initiated a special study in 1993 near the American
Smelting and Refining Company (ASARCO). The Vilas Elementary School, about two miles southwest of the plant, was
the site chosen for the study. The study showed that arsenic levels consistently exceeded both the annual and 24-hour
screening levels. During a permit hearing, the company agreed to reduce arsenic emissions by a factor of ten.* Today,
the company is not even operating and various lawsuits are seeking clean-up of dust and contaminated soils near the company.
Finally, the TCEQ also uses its mobile laboratory units to monitor air toxics. Overall, the TCEQ has nine mobil monitors.
The mobile monitors allow the agency to do intensive, pollution-source-oriented monitoring trips downwind of industrial facilities, often in response to complaints by citizens.* Between January 1995 and August 1997, for example, the then-TNRCC conducted nearly 60 mobile monitoring studies throughout the state for a variety of toxic and criteria
pollutant compounds. Tests conducted near chemical companies in August and October 1996 in the Beaumont-Port
Arthur area and in February 1997 in Corpus Christi led to citations against six companies for violating sections of the Texas Clean Air Act.*
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