Houston Sees Record Low Ozone

Houston Sees Record Low Ozone
February 1, 2009

The Houston metropolitan area, often cited as having the nation’s most polluted air, exceeded federal ozone standards for a record-low 16 days in 2008.

The official tally from the Texas Commission on Environmental Quality contradicts a recent claim by the Houston Chronicle that “the region’s goal of consistently healthy air remains elusive.”

Ever-Tightening Standards

The Houston air quality data show only six days exceeded the original one-hour ozone standard set by the Environmental Protection Agency in 1971. Even under today’s stricter standards, the 2008 data show significant long-term improvement.

Nevertheless, EPA’s ozone standard is set to become even stricter, as the agency recently lowered the federal ozone standard from 85 to 75 parts per billion. Under the new standard, Houston would have recorded 23 ozone-exceedance days in 2008.

Not the ‘Smog Capital’

Under the old one-hour standard, Houston in 1999 would have overtaken Los Angeles for the most days exceeding federal ozone standards. In 1997, however, EPA had already adopted the eight-hour standard (85 ppb), which the agency began enforcing in 2004. Based on the eight-hour standard, Los Angeles, Fresno, and Bakersfield, California consistently have had more ozone-exceedance days than Houston.

Air quality expert Joel Schwartz of the American Enterprise Institute said Houston has been getting undeserved criticism for its air quality. Schwartz says the Houston metropolitan area had a few more days in which at least one location exceeded the one-hour standard, but a tally of exceedances at each region’s single-worst location shows Los Angeles has always had more ozone than Houston, even under the one-hour standard.

Schwartz said it is misleading to count an exceedance for the whole region when just a single monitor exceeds the standard, because that creates more total exceedances than any individual person ever experiences. “It’s like saying ‘it rains 365 days a year on Earth,’ based on the fact that it rains somewhere on Earth every day,” said Schwartz. “This is true, but it creates the false impression that most people get rained on every day.”

Schwartz said these misleading calculations “create the impression that Houston has been the nation’s ‘smog capital’ since 1999. But it was only in 1999 that Houston even came close to being the smog capital. Even by the invalid measure regulators used to declare Houston the smog capital in 1999, Los Angeles took back the ‘crown’ in all years after 1999.”

Ongoing Improvement

Houston, Los Angeles, and most of the United States have for years been achieving large annual reductions in nitrogen oxides and volatile organic compounds, the pollutants that form ozone.

Schwartz said ozone reductions have been slowing recently in many areas because ozone levels are relatively low compared to the past. The closer ozone levels are to background levels (about one-fourth to one-half of the ozone in the air is either natural or transported from other countries by the winds, said Schwartz), the harder it is to reduce ozone further.

Despite the ongoing declines in ozone and ozone-forming pollution, the continual tightening of air pollution standards makes it seem as if air pollution is getting worse, Schwartz notes. Each time EPA tightens ozone standards, the number of ozone-exceedance days goes up, even though actual ozone levels decline.

Thus the new EPA standard will cause ozone-exceedance days to jump sharply next year even though ozone levels are likely to continue their decline, Schwartz observed.

Overstated Health Harms

H. Sterling Burnett, a senior fellow at the National Center for Policy Analysis, says the federal ozone standard is set so low that exceeding it does not mean the air is dangerous to human health.

“Ozone levels are well below the level that can be expected to cause harm,” Burnett said.

Burnett noted the news media often claim ozone aggravates asthma, yet hospital admissions for asthma are lowest in July and August, when ozone levels are highest. “There is no correlation,” said Burnett. “In fact, there is an inverse relationship. Blaming ozone levels for asthma-related problems defies common sense.”

Burnett also noted natural weather patterns have a tremendous impact on local ozone levels. The dry, stagnant air that dominates Houston in the summer is a significant factor in ozone creation. “Some aspects of air pollution are not under human control,” said Burnett.


Drew Thornley (drewthornley@gmail.com) writes from Texas.