Multi-layered strategies and high-tech equipment focus on
the region
Even with a growing population and industrial base, the
Houston region is making headway in air quality improvements. Over
the years, the TCEQ has compiled an array of strategies and
high-tech equipment to tackle air quality problems. Here is an
update of those efforts, as well as a progress report on an
ambitious project to update the health screening values for a
number of key chemicals.
In this story:
Large Industrial Hub
Guidelines Protect Health
Getting Results
Sidebar: Health Screening Levels Take Shape
Multi-layered strategies and high-tech equipment focus on the
region Armed with advanced technology capable of detecting
emissions, two TCEQ investigators made a discovery last year that
surprised even the veterans in their field.
Jason Harris of the Houston regional office recalls that he and
a co-worker were conducting fence-line monitoring near the town of
Shoreacres, east of Houston. They were using an infrared imaging
camera that can find air pollution invisible to the human eye.
With the camera, called the GasFindIR, Harris and his colleague
saw significant amounts of emissions spewing from separator
equipment at a natural gas production facility.
A follow-up inspection showed that the industrial site had a
permit to release 25 tons per year of volatile organic compounds
(VOCs) and had been reporting emissions of only 4.7 tons. Testing
showed that in reality an estimated 386 tons a year of VOCs were
escaping.
The TCEQ began enforcement proceedings, and the company owner
installed a vapor recovery unit, which lowered emissions to an
allowable level.
Harris attributes the discovery and quick resolution to the
infrared camera, which the agency uses on a regular basis to assist
in locating unauthorized or previously unknown emissions from
industrial plants and marine vessels. With this technology,
environmental regulators can identify emissions that once were
difficult—if not impossible—to detect.
But this unique camera is just one approach to addressing air
quality issues.
Houston not only has the ongoing problem of ground-level
ozone—the area is in nonattainment of the federal 8-hour
ozone standard. But, there is also an abundance of industrial
facilities emitting various kinds of contaminants. One notable
example is benzene, a well-documented carcinogen that is a building
block for many products, such as packaging, compact disks, and
gasoline.
Benzene and other air toxics, like 1,3 butadiene, are not
regulated directly under the National Ambient Air Quality
Standards, but rather as hazardous air pollutants and through the
state's New Source Review permitting program.
The Environmental Protection Agency is required to control 188
hazardous air pollutants, or air toxics. In sufficient
concentrations, these pollutants could potentially cause a wide
variety of adverse health effects.
To track this category of pollutants, the TCEQ has assembled an
array of advanced monitoring tools. The agency also pursues
multiple strategies to get results, including soliciting industry
cooperation to find and reduce emissions.
Back to the top
Large Industrial Hub
Harris County and its neighboring counties are home to eight
petroleum refineries, three of which are listed among the 10
largest in the United States. Also more than 150 chemical
facilities in the area provide products for the domestic and
international markets.
Yet, even with steady growth—in terms of people, traffic,
and industry—the region continues to make progress cleaning
the air.
"With state regulations and enforcement activity, the levels of
nitrogen oxides have fallen 57 percent and VOCs by 38 percent since
2000," said David Schanbacher, the chief engineer at the TCEQ.
"This represents a total reduction of 675 tons per day of these
smog-forming pollutants."
Air quality also continues to improve, says Schanbacher, because
the TCEQ is aggressively targeting specific air toxics, such as
benzene. Some of the monitoring tools helping to pinpoint these
emissions in the Houston area include:
Infrared cameras. With the technology of the
GasFindIR camera, which was developed for the military, TCEQ
investigators can view emission plumes not visible to the naked
eye. The agency owns six cameras. Besides two at the Austin
headquarters used for field monitoring, there are two in the
Houston regional office, and one each in the Corpus Christi and
Midland regions.
Through an agreement with the U.S. Coast Guard, TCEQ
investigators are now able to conduct infrared-camera observations
of facilities along the Houston Ship Channel from Coast Guard
vessels. This way, state investigators can get much closer to
facilities on the water.
The infrared camera has also been dispatched on aerial surveys
of industrial sites. In 2005, the camera helped identify more than
7,000 tons per year of ozone-forming emissions, including benzene.
Those emissions have since been eliminated.
For the public to understand how the agency intends to use data
generated by these cameras, the TCEQ has developed a
protocol (look under "GasFindIR Use Protocol").
Mobile monitoring. The TCEQ deploys up to eight
mobile monitoring vans to conduct monitoring for different
pollutant types, sampling upwind and downwind of specific
facilities to identify pollution sources. This practice is helpful
when there is no stationary monitor in the proximity or when a
stationary monitor has identified key pollutants in a highly
industrialized area. In a cluster of facilities, it can be
difficult to pinpoint a pollution source with just a stationary
monitor. Agency vans drive outside a company's fence line, with
monitors positioned according to the wind direction, to pinpoint
sources of elevated emissions.
Differential absorption lidar (DIAL). This
mobile monitoring unit combines infrared and ultraviolet laser
technology to scan industrial facilities and measure emissions from
sources such as storage tanks, flares, and cooling towers. After a
five-week trial last year, the TCEQ is reviewing DIAL monitoring
data to determine whether calculation methods used to estimate
emissions result in the underrepresentation of some sources that
are difficult to monitor.
These various types of mobile equipment complement a broad array
of stationary monitors in the region, some of which calculate
hourly averages of emissions day and night. The TCEQ and partners
in local government and industry operate stationary air samplers
that together make up one of the largest monitoring networks in the
world. The system includes monitors capable of triggering e-mail
alerts when concentrations spike, so that the TCEQ and its partners
can quickly look for the emissions source.
In another development with the Coast Guard, the maritime agency
is helping the TCEQ pinpoint emissions from vessels traveling the
Houston Ship Channel. The TCEQ hosts data from several
industry-sponsored monitors, one of which is an automated gas
chromatograph at the Lynchburg Ferry, where the ship channel meets
the San Jacinto River. Using real-time data, the monitor issues an
alert when it detects elevated concentrations of benzene.
The Coast Guard checks wind direction and provides a radar
picture of the tugboats and towboats that were in the vicinity at
the time of the concentration spike.
Because the state does not regulate marine vessels in transit,
the TCEQ assigns its pollution prevention team, which has no
enforcement authority, to contact the tug, tow, and barge owners to
gather information on what the barge was carrying, and where it was
traveling to and from. Through this approach, the TCEQ may be able
to determine whether barges carrying benzene products are
contributing to benzene levels in the air.
American Waterways Operators has agreed to work with the TCEQ on
this project. The TCEQ, along with the Louisiana Department of
Environmental Quality, has also assisted this organization with
creating a guidebook of best management practices to help reduce
inadvertent emissions from tank barges.
Back to the top
Guidelines Protect Health
The TCEQ uses scientific data to establish health-protective
levels of exposure for air pollutants. These "effects screening
levels" are also known as ESLs (see "Health Screening
Levels Take Shape.")
The agency relies on ESLs and state regulatory standards to
designate areas for the Air Pollutant Watch List and to set
enforceable industrial air permit limits.
When an air quality monitor measures trends that exceed an ESL,
the TCEQ places the surrounding area on the Watch List for stricter
inspections, monitoring, enforcement, and permitting reviews.
Of 14 monitoring locations on the Watch List in Texas, five are
in Harris, Galveston, and Brazoria counties. In just the
Houston-Galveston Watch List areas, the annual averages for benzene
were 20 percent to 48 percent lower in 2006 than in 2005. There
were further improvements in 2007. One additional area in Galveston
County was removed from the Watch List in 2007 after monitoring
data showed sustained benzene reductions.
When monitored levels fail to decline, the agency takes
additional steps, such as aggressive use of state-of-the-art
monitoring equipment, to find and implement controls on previously
underestimated or unknown emissions.
Back to the top
Getting Results
An important part of the TCEQ's strategy has been to work in
cooperation with industry, and those efforts are paying off on the
east side of Houston.
In the Milby Park and Manchester neighborhoods, voluntary
agreements obtained with local companies resulted in lower levels
of 1,3 butadiene at the nearest downwind monitor—a drop of 75
percent annual average concentrations from 2004 to 2007.
This occurred after a series of meetings with large firms that
had been identified as potential sources. The resulting agreements
established specific timelines for the facilities to reduce
specific emissions and/or implement additional controls, such as
flare gas recovery systems and improved controls on flare and
wastewater emissions. Companies also agreed to install their own
fence-line monitoring and to use infrared cameras to find
leaks.
From 2005 to 2007, benzene levels at the Lynchburg Ferry monitor
measured a 52 percent reduction. The agency used monitors and the
infrared camera to target potential sources in this heavily
industrialized area, which includes barge operations, tank
facilities, chemical plants, and petroleum refineries. TCEQ
enforcement activities, industrial emission-reduction agreements,
and a collaborative effort with area industries to identify and
control emissions all contributed to this achievement.
In the process of focusing on pollution sources, owners of
industrial facilities often find they ultimately save money by
locating leaky equipment. In the Shoreacres investigation, once the
emissions problem was resolved, the company was no longer losing
valuable raw product. In these cases, the pollution control
equipment pays for itself in short order.
"With all the resources devoted to the Houston area, we can say
there has been significant progress in air quality, including air
toxics. But much remains to do," said Schanbacher. "That is why the
TCEQ continues to look for ways to protect the environment and
reduce pollution. We do this relying on health-based data and
state-of-the-art monitoring tools to prioritize our investigations
and regulatory actions."
Back to the top
Health Screening Levels Take Shape
Revised guidelines for air quality will better protect
public health
Toxicologists at the TCEQ are working on a project to update the
health screening values for key chemicals—air pollutants that
are closely tracked by many of the air quality monitors in Texas or
are frequently permitted.
Among these are toxic air pollutants—chemicals that are
known or suspected to cause cancer or other serious health problems
in sufficient concentration and exposure.
The project is part of an ambitious re-examination of the
agency's "effects screening levels," or ESLs. These levels are
chemical-specific air concentrations established to protect the
public's health. ESLs are established for air pollutants that are
not regulated by federal ambient air quality standards.
The agency's ESLs are set well below levels that would cause
adverse health effects. When monitored levels of a chemical exceed
its ESL, that triggers further evaluation of actual risk and, if
appropriate, emissions reductions. ESLs play a leading role in
evaluating air monitoring data, setting emission limits in air
permits, and determining safe cleanup levels during remediation
projects.
TCEQ management decided in 2003 to update the 30-year-old ESLs.
That decision started agency toxicologists on a two-year review of
all known methods of deriving health-protective values. Their
resulting methodology won the approval of a scientific peer
review.
In 2006, after two rounds of public comments, the TCEQ completed
new guidelines for developing ESLs. For chemicals that may cause
cancer, the agency adopted a cancer-risk level of 1 in 100,000,
which is the midpoint in the Environmental Protection Agency's
range of 1 in 10,000 to 1 in 1,000,000.
Under the TCEQ risk level, if 100,000 people were continuously
exposed for a lifetime to a concentration of a carcinogen equal to
the ESL, there would theoretically be one case of cancer—in
addition to the current U.S. rate for all cancers of 30,000 to
40,000 for every 100,000 people. Exposure at the 1-in-100,000 level
is unlikely to cause adverse health effects in the general public.
The TCEQ rejected the 1-in-10,000 level as not sufficiently
health-protective.
Examining the ultra-low 1-in-1,000,000 risk level led to
conclusions that using this risk level would result in
unenforceable violations at most air toxics monitors. For example,
the TCEQ is barred by federal law from setting emission standards
for cars and trucks. Yet at many monitors across the country,
including those in rural and suburban areas of Texas, benzene
exceeds the 1-in-1,000,000 risk level due to vehicle emissions
alone.
By the end of 2007, the toxicology team had completed nine ESLs,
including one for benzene, that meet the health-protective
1-in-100,000 risk level. Another 10 ESLs, which include 1,3
butadiene, were submitted to the public for comments in January
2008. Work is under way on 11 more ESLs.
Once completed, the new ESLs take effect immediately.
The ESLs for benzene and 1,3 butadiene have drawn considerable
attention because both are known human carcinogens. Industrial
facilities in Harris County produce more of these two compounds
than any other location in the country.
Back to the top
