Editor’s Note: This is the second part of a two-part series produced in partnership with the Center for Public Integrity. Read part one here.

The testimony sounds the refrains of industry groups: Tightening the country’s smog standard would be too costly, and it isn’t necessary for public health.

But these comments weren’t from industry. They were written by the chair of the Texas agency responsible for environmental protection.

The state of Texas is as aggressive as some industry associations in battling a proposed tightening of health standards for ozone, the main ingredient of smog. Officials there have spoken before Congress, hired a consultant firm to question the health benefits of a more stringent standard—the same firm hired by the American Petroleum Institute—and introduced bills to fundamentally change how ozone is regulated nationwide.

This is a long-standing strategy for Texas, where power plants, cement factories, refineries, and other facilities produce far more ozone-causing pollutants than those in any other state, according to a Center for Public Integrity analysis of U.S. Environmental Protection Agency data. Texas officials have butted heads with the EPA over ozone since the 1970s.

“They’ve been fairly consistently against clean-air protections,” said Elena Craft, a senior health scientist at the Environmental Defense Fund.

Though ozone levels are markedly better now, compared with past decades, parts of Texas, particularly in the Dallas-Fort Worth and Houston areas, have some of the nation’s highest readings.

The Texas Commission on Environmental Quality said in an emailed statement that it’s trying to ensure that rules are necessary before they’re imposed.

“TCEQ has concluded that there will be little to no public health benefit from lowering the current standard,” the agency’s chairman, Bryan Shaw, said in written testimony at a December Senate hearing.

More Industrial Emissions Than Any Other State

Nitrogen oxides (NOx) and volatile organic compounds (VOCs) form ozone at ground level as they cook in the sun.

Cars are a major source: Highway vehicles account for about 40 percent of NOx and 15 percent of VOCs in the United States, according to EPA figures. But power plants, factories, oil refineries, and other industrial facilities are big contributors too.

View Images An oil laborer works on an oil derrick in Texas. The state's environmental commission has aligned itself with the oil industry and other manufacturers in opposing a tighter ozone standard. Photograph by Sarah Leen, Nat Geo Image Collection

That’s particularly true in Texas, according to 2011 EPA data, the most recent.

Texas’s 340,000 tons of NOx emissions from facilities’ stacks and vents topped the emissions in number two Pennsylvania, home of big coal-fired power plants, by more than 60 percent. At 105,000 tons, VOC emissions from facilities in Texas were 44 percent higher than those in number two Colorado, even though Colorado—another oil and gas hub—had far more sources producing those pollutants.

California has a greater number of facilities emitting NOx than any other state—more than twice the number Texas has, according to the EPA data. And yet California’s collectively spew a quarter of the NOx emitted by Texas facilities. It’s a similar story with VOCs.

“Because we have had such a bad air-quality problem for many years, there’s been a lot of strict controls that have been put into place,” said Sylvia Vanderspek, chief of the air-quality planning branch at California’s Air Resources Board. “So our stationary sources are very well controlled.”

In Texas, the commission points to the state’s success in reducing emissions. Annual NOx from facilities totaled 900,000 tons as recently as 1998, but they’ve dropped since the EPA’s tally and are now below 300,000 tons, according to the state’s data.

Ozone levels have dropped as a result, improving 24 percent between 2000 and 2013, according to the TCEQ. That improvement came as the state added more than 5.5 million people and their ozone-contributing vehicles.

Still, California cut ozone levels faster.

The Los Angeles region has the nation’s worst ozone levels. But the rest of California had less smog than Texas’s Brazoria County, near Houston, and the Dallas-Fort Worth suburb of Denton County in 2011-13.

Pollutants by state Texas, which opposes a tighter health standard for ozone, the main ingredient of smog, produces more ozone-causing pollutants from the vents and stacks of factories, power plants, and other facilities than any other state. Nitrogen oxides, known as NOx, and volatile organic compounds, or VOCs, combine to form ozone when cooked in the sun. Nitrogen oxides (NOx) Data in tons of industrially produced emissions in 2011 Vermont 649 350,000 200,000 75,000 300 mi Texas 340,494 300 km Top 10 states Volatile Organic Compounds (VOCs) Data in tons of industrially produced emissions in 2011 350,000 200,000 75,000 DC 68 Texas 105,945 Top 10 states Source of Emissions Nitrogen oxides and volatile organic compounds form ozone when mixed with sunlight. In the United States, the major man-made sources of those emissions are automobiles and industrial facilities. Industrially produced emissions in 2011. Hover over the bars for complete breakdown of data. Nitrogen oxides (NOx) Mobile sources 60% Stationary industrial sources 34% Other 6% Volatile Organic Compounds (VOCs) Mobile sources 29% Stationary industrial sources 50% Other 21% NG STAFFSOURCES: EPA; CENTER FOR PUBLIC INTEGRITY

Tom “Smitty” Smith, the Texas office director for the consumer advocacy group Public Citizen, credited Texas with doing “some very aggressive things” to attack smog. But “overall,” he said, “the state has failed to live up to its obligations to protect its citizens from poor air quality.”

The Ozone Fight

In 2013, the TCEQ gave a consulting firm, Gradient, a two-year contract worth up to $1.65 million to “critically review” the science behind the EPA’s ozone and other air-pollution standards. The EPA has proposed to tighten the ozone standard from 75 parts per billion to between 65 and 70 ppb.

Gradient wrote reports for the American Petroleum Institute, the Utility Air Regulatory Group, and other industry associations in the past several years, arguing that the EPA overstated ozone risks by relying on studies with limitations.

Gradient principal Julie E. Goodman, a toxicologist, co-wrote a Wall Street Journal opinion piece last year saying the “overwhelming body of scientific evidence” suggests the current standard is sufficient. A PowerPoint presentation she made to the TCEQ last fall pointed to the studies’ limitations and “inconsistent” results.

Ozone researchers, however, disagree. The evidence of health risks above 60 ppb “is clear,” said Mary B. Rice, a pulmonary critical care physician at the Harvard-affiliated Beth Israel Deaconess Medical Center, in Boston.

View Images Texas oil refineries, like these in Corpus Christi, are a major industrial source of nitrogen oxides and volatile organic compounds, which react to form ozone. Photograph by Sarah Leen, Nat Geo Image Collection

Texas doctors have become increasingly vocal about the issue. This year the Dallas County Medical Society called on the EPA to tighten the standard and urged the state to take more aggressive actions to battle smog, rather than smog rules.