*Clarification appended

Texas officials and lawmakers are continuing to protest tougher federal ground-level ozone standards, three weeks after the Environmental Protection Agency unveiled its new regulation to cut down on smog that chokes the nation’s skies.

Their main tactic? Trying to poke holes in the scientific consensus behind the regulation.    

U.S. Rep. Lamar Smith, R-San Antonio, aimed to do just that Thursday while leading a hearing of the House Committee on Science, Space and Technology, which he chairs. He accused the EPA of “cherry-picking” studies to support a political agenda. 

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Ozone forms when emissions from cars and industrial plants mix with other airborne compounds in sunlight, and it’s known to worsen asthma, lung disease and heart conditions.

A standard finalized this month shrinks the ozone limits to 70 parts per billion, putting pressure on some regions in Texas that struggled to meet the previous standards.  Though the new regulation is more lenient than environmentalists called for, Texas leaders have joined with industry in blasting the regulation, arguing it will cost billions of dollars to invest in cleaner technology that will yield fewer health benefits.

At Thursday's hearing, Smith called on the top authority on pollutants for the Texas agency charged with protecting the environment.

“There remains large uncertainty and scientific invariability in the literature,” Michael Honeycutt, chief toxicologist of the Texas Commission on Environmental Quality, told the committee. “The results from these studies are also contradictory and inconsistent.”

But Democrats, including a member from Texas, called the effort misleading and compared it to the tobacco industry’s decadeslong crusade against science linking its products to lung cancer.

“The committee has become a major forum for rolling out these tactics,” U.S. Rep. Eddie Bernice Johnson, D-Dallas, said at the hearing, criticizing Texas regulators for joining in. “Americans are not fooled by these tactics anymore.”

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The hearing was titled “EPA’s 2015 Ozone Standard: Concerns Over Science and Implementation.”

A fierce battle over ozone regulations has raged since the George W. Bush administration set the allowable standard at 75 parts per billion in 2008. It was a hugely controversial step that dismissed a unanimous advisory panel of scientists and doctors who said the standard should have been far lower. Under the rules, states must submit plans showing how communities will meet the standards. 

A federal court partially agreed with the scientists in 2013, but by then, it was already time to update the National Ambient Air Quality Standards, which limit pollutants such as ozone and must be reviewed every few years.

“Ozone pollution means it hurts to breathe for those most vulnerable: our kids, our elderly and those suffering from heart and lung ailments,” EPA Administrator Gina McCarthy, said when rolling out the new standard. “Our job is to set science-backed standards that protect the health of the American people."

But Texas continues to challenge that science.

The state's environmental agency has said the new regulation "makes no sense." 

"TCEQ’s own science and data show that the new standard will have minimal — if any — health benefit," the agency said in a statement this month. 

Its battle against new standards has included, as The Texas Tribune has reported, paying a research firm $1.65 million to look for holes in the science behind the standards. The Massachusetts-based firm, called Gradient, typically conducts research funded by industry groups like the American Petroleum Institute. 

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On Thursday, Honeycutt said he wasn’t questioning the fact that ozone can harm human health in general but argued that tightening the standard to 70 parts per billion would not yield enough health benefits to justify the cost to industry and consumers. Honeycutt also accused the EPA of basing the revision on just one study, and cherry-picking the data.

Elena Craft, a health scientist who specializes in air pollution at the Environmental Defense Fund, took issue with that characterization.

“The idea that we’re relying on just one study is just not accurate,” she testified. “There is strong, scientific consensus that the ozone standard must be significantly strengthened.“

The EPA says it has reviewed thousands of papers, including those on ozone’s effects on respiratory, cardiovascular, nervous system effects and links to early deaths. The agency summarized the studies in its “Integrated Science Assessment” before gathering hundreds of thousands of public comments and holding a series of public meetings.    

Honeycutt argued that most of those studies don’t directly support the 70 parts per billion standard.

Millions of people in the U.S. — including those in Houston, Dallas and San Antonio — live in areas that struggle to meet the previous standards. Some communities have seen improvement, but health problems persist. In the Dallas-Fort Worth area alone, more than 1.1 million people struggle with asthma, heart disease and lung disease.

El Paso, Austin and swaths of East Texas that may have immediately struggled to meet a slightly lower threshold, which some EPA watchers expected when the rule was proposed, appear to be spared under the final rule, which applies to three-year averages.

Depending on the severity of their ozone problems, regions would have to meet the lower standards sometime between 2020 and 2037.

Neena Satija contributed to this report. 

Clarification: This story was updated to clarify that Texas Commission on Environmental Quality chief toxicologist Michael Honeycutt accused the EPA of basing its revised ground-level ozone standard on just one study, and cherry-picking the data.

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