L.A. Tops Houston as Nation’s Smoggiest City

The presidential campaign isn’t the only close, politically charged race heating up these days. In a tight contest, Los Angeles has, for the moment, overtaken Houston for the dubious distinction of smog capital U.S.A.

Summer still has plenty of dirty air to go around in both cities, but so far this year the Southland has posted eight more days of unhealthful ozone than its Texas rival, although Houston’s worst smog has been dirtier than any in Southern California, according to air quality officials.

Last year, for the first time, Houston had more smoggy days and higher peak readings than Los Angeles--a record that has become a weapon in the presidential election, as Democratic nominee Al Gore accuses Texas Gov. George W. Bush, the Republican nominee, of presiding over the nation’s worst pollution.

The Nov. 7 presidential election will be nearly here by the time smog season has run its course in both cities. Which city loses the race will be determined in large part by simple changes in the weather.

“It’s really kind of a horse race now between the two cities,” said Joe Cassmassi, senior meteorologist for the South Coast Air Quality Management District.

For now, Los Angeles has a solid lead. As of Tuesday, the most recent date available to make comparisons, the four-county Los Angeles region posted 34 days in 2000 when air exceeded the national health-based limit for ozone, compared with 26 for Houston. The worst air actually occurs far inland, especially in Crestline, the east San Gabriel Valley and Hemet.

Ozone is but one ingredient in the chemical soup over many U.S. cities, but it is closely watched because it is so pervasive, and because health studies show it damages the lungs.

But overall, the more than 3 million people living in the Houston area appear to be breathing slightly larger amounts of the pollutant this year. The maximum single-day ozone reading, an indicator of high concentrations of smog, in Houston to date was 208 parts per billion. This is 73% higher than the federal standard and greater than the Los Angeles region’s peak of 180 parts per billion.

Both cities have enjoyed some respite lately. Rain has helped cut pollution over Houston this week, while subtropical monsoons inching up from the Gulf of California have helped short-circuit smog-forming conditions over Los Angeles.

Each city is a smog-making machine, but for different reasons. In Houston, much of the pollution comes from oil refineries, petrochemical plants and the ships that supply them. Emissions generated near the coast blow inland, mix with fumes from cars, paints and other household products and linger over the city.

In Los Angeles, ozone is formed when exhaust from tailpipes and smokestacks released during the day mixes with other chemicals and sunshine. Sea breezes push that pollutant, as well as dust and soot that form haze, to inland valleys where it stacks up against mountain ranges and becomes trapped beneath a sinking lid of warm air called an inversion layer.

For decades, California reigned supreme as the nation’s dirty air leader, but Houston and other cities have closed the gap in recent years.

In 1999, Houston overtook Los Angeles for the smog lead for the first time when it posted 52 days of unhealthful ozone, compared with 41 in Los Angeles, as well as higher peak concentrations of the pollutant.

California has spent billions of dollars and pressed hard on numerous fronts over the past 50 years to curb ozone-forming emissions. Control measures have been approved for everything from bakeries to paint cans, deodorant to transit buses, gasoline cans to perfume. The state is now home to the cleanest cars, cleanest gasoline, some of the cleanest consumer products and the most regulated industries in the nation.

In contrast, refineries in Houston are 10 to 20 years behind Los Angeles-area refineries in pollution control, and industrial plants continue to spew large volumes of pollution. Lax controls predate Bush, who became governor in 1994. But critics contend that Bush, a former head of an oil and gas exploration company, did little to change those policies until federal authorities threatened to cut off highway funds if Texas failed to meet clean-air deadlines. Texas is developing new initiatives, from voluntary pollution controls at factories to cleaner cars, to meet Clean Air Act requirements.

In Southern California, the final week of August and first couple of weeks of September are historically the smoggiest of the year. Subtropical clouds and moisture from Mexico will be gone by then, and strong onshore ocean breezes, which can blow smog away, usually die out. The results are stagnant days that could deliver a big pulse of dirty air, said Cassmassi of the South Coast district.

“The next few weeks are the last shot we really have at having any high numbers. After that the numbers will really die down,” Cassmassi said.

But in Houston, smog season lasts much longer. It is not unusual to see unhealthful air begin in February and persist into September, or even November. Indeed, lots of smoggy days heading into autumn last year clinched Houston’s position as the nation’s smog leader.

Of more immediate concern, scientists are closely watching tropical storm Debby as it churns toward the Bahamas. If it enters the Gulf of Mexico, it could spell smog trouble for Houston. Swirling winds from tropical storms typically pull air pollution from the Midwest and the South toward the Texas coast, Lambeth said, and it is not uncommon to see ozone levels spike during those events.

(BEGIN TEXT OF INFOBOX / INFOGRAPHIC)

The Outcome Is Unclear

Los Angeles is on a pace to displace Houston as the nation’s ozone capital because of the return of hot, stagnant air across the Southland this year. But lots of smoggy days await, and Houston, which surpassed Los Angeles as the nation’s most polluted city for the first time last year, may yet retain the dirty-air crown.

Note: ppb means parts of ozone per billion parts of air.

Sources: South Coast AQMD; Texas Natural Resources Conservation Commission