No city keeps its air to itself. Plumes of air peppered with ozone, with tiny soot particles from diesel engines and with other contaminants are known to travel hundreds, and sometimes thousands, of miles.

As a result, dirty air from Houston or Horseshoe Bay, Texas, can trade places with that in Hammond or Harrisonburg, La., and vice versa.

Dr. David Allen, in front of trailers being equipped to take air samples and evaluate meteorological conditions for a new study of Eastern Texas air quality. Allen holds the Melvin H. Gertz Regents Chair in Chemical Engineering.

Photo: Jennie Trower

That knowledge has led federal and state government agencies to begin pursuing multi-city air studies. They want to understand how air from elsewhere will affect their ability to prepare for more stringent air-quality requirements from the Environmental Protection Agency (EPA) as it grows more aware of how harmful bad air can be.

One of the largest regional studies under way is being conducted by air-pollution experts at The University of Texas at Austin, who came together this past spring with hundreds of colleagues from universities, state and federal agencies and elsewhere. The University of Texas at Austin is one of the lead institutions of the group that has begun probing the skies above tens of thousands of square miles of Eastern Texas, on the heels of a similar study done last year by others to examine transatlantic movements of air pollutants in the northeastern United States.

Five years ago, chemical engineer David Allen led a 30-member team that produced a Houston-focused study that changed the state’s regulatory decisions for the ozone-challenged city. They successfully provided credible findings, but just as important, were able to effectively communicate them to policymakers. As a result, the group was tapped to play a leading role in this larger study.

“In 2000, we demonstrated that sound scientific information can be like a compass, guiding state regulatory decisions” said Allen, who directs the university’s Center for Energy and Environmental Resources, “and what we want to do is make sure that a scientifically based approach continues to be used to inform decisions.”

Why Care About Air

The average adult breathes in thousands of gallons of air each day. The body absorbs the air’s oxygen through the lining of the lungs, so the oxygen can travel to the body’s cells and fuel activities. Throw in a dangerous pollutant such as ozone, and breathing and other bodily processes become compromised.

Cities can gain some bad air from elsewhere. Here, the black lines demonstrate the path that dozens of air parcels containing unhealthy ozone levels traveled for 32 hours into Austin from other Texas cities, Louisiana and farther reaches. Air parcels shown contained an average of more than 75 parts per billion of ozone for at least eight hours, based on measurements taken between 1993 and 1999. Watch video of changes in ozone levels. [Download QuickTime Player.]

Short-term exposure to ground-based ozone, the main ingredient in smog, can cause coughing, shortness of breath, worsened asthma attacks or irritation of the eyes, throat and nose. About a third of Americans suffer from more severe problems after long-term ozone exposure, such as poor lung function and respiratory infections. But ozone can make anyone sick, including about 20 percent of healthy adults, and is especially hard on children and the elderly.

Ozone is a highly reactive chemical that forms when chemicals called nitrogen oxides and volatile organic compounds react in the air. Power plants, cars, construction equipment and other sources that burn fuels release nitrogen oxides. Nitrogen oxides turn ozone-forming when they react with compounds that contain carbon, known as organic compounds.

The particular carbon compounds involved are called volatile organic compounds for their ready ability to become a gas that enters the atmosphere. These volatile compounds are most commonly released as unburned fuel from cars, as byproducts of factories manufacturing products like perfumes and plastics, as paint fumes and as a result of the respiratory activities of trees and plants.

Tracking down where ozone originates is complicated by the many chemical sources that can create it. Ozone also results from sunlight “cooking” ozone-generating chemicals under stagnant conditions. So wind and other quickly changing weather factors influence where ozone forms, and where it and other pollutants spread once formed.

“You have to take all the different chemical and meteorological data into account to try to make heads or tails of air-pollution data,” said Allen.

Did you know…? The average adult breathes about 3,400 gallons of air a day. The Clean Air Act of 1970 is estimated to have provided Americans with health benefits of $23 trillion by 1990, or more than $1 trillion a year. Children, who often are active outside, and the elderly, who may have lung or heart disease, are more readily harmed by air pollution. So are runners or others who do strenuous activity in polluted air. For outdoor exercisers, limit activity when the air quality index is above 150, and avoid it at levels above 200. Regardless of the ozone level, avoid exercising near congested highways, and know that it is better to exercise early in the morning, before vehicles and industrial facilities start emitting chemicals that help produce ozone. Keeping your car in good shape matters. About 10 percent of cars on the road produce 60 percent of the ozone-contributing chemicals to the atmosphere. Information compiled from Dr. David Allen, the EPA and the American Lung Association.

The goal of improving peoples’ lives is what he said keeps him going despite the seven-day work weeks his research and outreach has required since 2000.

“What I get greatest satisfaction from is seeing the work we do result in real air-quality improvements in places like Houston, and now Dallas-Fort Worth and Austin, affecting potentially millions of people,” Allen said.

Covering All Bases

The regional Texas air quality study that Allen and others began this April at the start of the ozone season will monitor the air over the homes of about 10 million Texas residents. The study area is bounded by Interstate 35 and Interstate 37 on the west, and includes parts of Austin, Corpus Christi, Fort Worth and San Antonio, and all of cities such as Dallas, Houston and Longview.

This Texas Air Quality II study is designed to provide the most complete understanding of how ozone and other pollutants travel long distances between Texas communities, and into and out of the state.

The air evaluations are being carried out by land, by sea and by air at an anticipated cost of more than $35 million. The equipment involved will include dozens of ground-based measuring stations, with Allen’s group outfitting new trailers with monitors to be sent each month into the field for this purpose. The monitors evaluate meteorological conditions and check for the presence of solid particles and chemical pollutants in the air.

Other measurements will include satellite tracking of plumes from fires and other sources in less-urban settings, four aircraft probing large swaths of cities’ skies, and a National Oceanic and Atmospheric Administration research vessel investigating shoreline emissions and air pollutants over the Gulf of Mexico.

While sampling will be going on continuously for the next year, the most intensive sampling will be done in August and September 2006, and fed into a database managed by the Texas Commission on Environmental Quality. 

A formal scientific briefing on the study’s findings is planned for October 2006. But the real-time nature of the data means Allen and his colleagues can start informing the Texas Commission on Environmental Quality and other state regulators about findings as soon as data permit.

“We’re shooting to inform as many air pollution regulatory decisions for different cities as we can,” said Allen, who spearheaded summary documents for the Houston study and will play a leadership role in preparing documents for the regional study.

Tailor-Made Planning

A stream of air is detected by a plane traveling over Houston. The plane uses laser-based equipment to detect ozone levels at multiple heights underneath it while traveling eastward from 4:20-4:32 p.m. on an August 2000 day.

The study will provide air quality information for cities throughout eastern Texas, but the investigators expect that not all the cities’ air problems will be alike, a fact the Houston air pollution study conducted by this team in 2000 had made clear.

At the time that the $30 million study began, Houston had just surpassed Los Angeles as America’s worst-air city. Houston, like several Louisiana cities, had a unique set of airy details to evaluate. It has a heavy industrial focus, and a coastal location with sea breezes that complicates the weather and makes it difficult to understand pollutant formation and movement.

In spite of the difficulties, Allen and others participating in the larger Texas 2000 Air Quality Study accepted the challenge, hoping to bring healthier, cleaner air to Houston residents. The group collected data from four planes that used a variety of devices to survey Houston air during hot, stagnant conditions in August and September 2000. That detailed data were combined with meteorological and air measurements from more than 50 ground-based sites, including one atop a sky scraper and several near the Ship Channel where many factories were based.

To everyone’s surprise, those factories turned out to be Houston’s main Achilles’ heel—not the pollution sources originally suspected, such as auto emissions. And the factories’ ozone instigators included certain types of volatile carbon compounds called highly reactive volatile organic compounds, rather than just the nitrogen oxides previously suspected.

“Some of the measurements were surprising enough that we spent months quality-assuring the data and making certain everything was right,” Allen said. “But it became clear very quickly that the regulatory plan for Houston the state had spent several years developing, based on our previous best understanding of what the atmospheric chemistry and physics was, would not be effective.”

Dr. David Allen with Jarett Spinhirne, a research engineer who runs Allen’s air analysis lab. In front of them is a device to which they have attached stainless steel cannisters that contain air samples collected at sites in Austin, Houston and other parts of central and eastern Texas for the TexAQSII study. The tank of liquid nitrogen behind that is used to cool the air sample down to -320 degrees Fahrenheit to solidify the carbon-based chemical pollutants in the air sample.

Photo: Jennie Trower

The experts were also stunned by the pattern of pollutant release. Some manufacturing plants in the Ship Channel had emission spurts, and emitted about 600 percent more highly reactive volatile organic compounds overall than anticipated. The extra starting material meant Ship Channel-related ozone could be formed at four times the rate of other cities evaluated (up to 150 molecules of ozone were formed per hour per billion air molecules near the channel, compared to an average maximum of 40 parts per billion per hour in cities such as Atlanta, Nashville and Phoenix).

Reaping the Scientific Reward

The Houston study and resulting summary documents for legislators, regulators and others helped the state to shift its regulatory focus to the specific hydrocarbons identified as Houston’s prime ozone instigators.

Vincent Torres, associate director of the University of Texas at Austin’s Center for Energy and Environmental Resources, said, "That approach is like using a rifle to get the greatest bang for the buck, rather than peppering a field with a shotgun blast."

Not only was the approach deemed wiser than just tightening pollution restrictions on nitrogen oxides , but a study by University of Chicago researchers estimated that Texas would save about $2 billion annually with the more tailored approach.

Meanwhile, cities like Austin, Texas, are adding auto-emission inspections into their regulatory repertoire, while other cities consider changing the composition of gasoline and diesel fuels to improve air quality. The new East Texas study will examine the value of all these measures.