When a Johns Hopkins University researcher published a study showing race and income as risk factors for asthma, she started getting phone calls from industry groups opposing U.S. EPA's bid to tighten the national ozone standard.
Dr. Corinne Keet said her newfound fans wanted to use her work to show EPA's ozone proposal wouldn't yield public health benefits.
A pediatrician who specializes in allergies, Keet is not an air pollution expert. Her study published in January in the Journal of Allergy and Clinical Immunology didn't even mention ozone.
"It's been an interesting education for me in terms of how research is interpreted," Keet said in an interview. "I was called by consultants for industry to discuss the results in terms of looking for ways of suggesting that either genetic factors or poverty rather than pollution are important things for asthma."
EPA has proposed tightening the national air quality standard for ozone -- a component of smog -- to between 65 and 70 parts per billion from 75 ppb set by the George W. Bush administration in 2008. Based on a scientific review, EPA said the 75 ppb limit was no longer adequate to protect public health as the Clean Air Act requires.
Industry groups and congressional Republicans oppose the EPA proposal, arguing that ozone isn't a significant factor in whether people develop asthma and citing Keet's study. The bottom line in aggressive media ads and messaging on Capitol Hill: Asthma rates are rising even while air pollution levels are falling.
Their campaign targets the Obama administration's assertion that a tighter ozone standard will help reduce hospital visits and other health care costs tied to asthma.
"When they start saying 'asthma,' of course that's a very compelling story. And the administration likes to tout that," said Howard Feldman, director of regulatory and scientific affairs at the American Petroleum Institute. "That's not necessarily borne out by all the information, the science out there. The trends are not there."
Public health advocates, on the other hand, maintain that foes of the tougher pollution standard conflate two different issues: asthma prevalence -- whether a person develops asthma -- and asthma exacerbation, whether someone who has asthma experiences an attack.
Environmental and health groups want a tougher ozone standard than what the administration proposed because it would improve life for people who have asthma and other respiratory diseases.
The Sierra Club, for example, in April launched a campaign meant to highlight "the challenges of being the working parent of a child with asthma" to coincide with Take Your Child to Work Day.
"We don't know what causes asthma, but we do know what triggers asthma attacks -- indoor pollutants, allergies, and we know that ozone is one of those triggers," said Paul Billings, senior vice president for advocacy at the American Lung Association. "It makes people vulnerable to some of those other triggers as well. Ozone's a powerful respiratory irritant, and people with asthma have sensitive lungs."
'Huge mess of things'
The Centers for Disease Control and Prevention estimates that 18.9 million American adults and 7.1 million children have asthma, according to a 2011 national survey.
Between 2001 and 2011, the CDC says, the number of Americans with asthma increased 28 percent.
Despite its prevalence, asthma remains a difficult health problem for researchers. What's commonly called asthma can involve a number of symptoms. And there's no single cause; whether a person develops asthma is likely the result of a confluence of factors.
But there's plenty of research tying exposure to ozone to worsening symptoms in asthma sufferers. A study published in March in the journal Environmental Health found that ambient ozone levels were associated with childhood asthma emergency room visits but that the relationships varied among boys and girls, as well as age groups.
David Peden, director of the University of North Carolina's Center for Environmental Medicine, Asthma and Lung Biology, said studies have so far shown no "absolute cutoff" for what level of ozone pollution harms asthmatics given that some people may have exacerbations at lower concentrations. But, he said, he had "very little doubt" that levels of ozone between 60 and 75 ppb could cause asthma attacks.
Peden has authored several studies on how air pollution affects public health, many of which have been funded by the National Institute of Environmental Health Sciences and EPA.
"Increased levels of ozone can sometimes sneak up on you," Peden said in an interview. "People know they're having an asthma worsening and may not appreciate that they're getting exposed to something that might be causing a very subtle irritation of the airway."
Public health groups have highlighted those connections in their campaigns calling for an ozone standard of no higher than 60 ppb. The American Lung Association, for example, has framed its campaign around kids wanting to play outside and their inability to do so when air pollution levels are high, particularly when children have asthma.
"We can do a lot to help patients manage their asthma. We can give them medication, they can use their devices correctly, but we can't control the ambient air," the association's Billings said. "Only through the power of collective action, through government, can we force the polluters to clean up and reduce that burden."
EPA says reducing ozone pollution to between 65 and 70 ppb would prevent between 750 and 4,300 premature deaths, between 1,400 and 4,300 asthma-related emergency room visits, and between 320,000 and 960,000 asthma attacks in children yearly by 2025. Taking into account reduced asthma attacks, EPA estimated that the benefits of the ozone rule would outweigh costs 3-1.
Industry, meanwhile, has focused its messaging on where the science is less certain: ozone's role in causing people to get asthma.
There's emerging evidence that air pollution has played a role in the upward trend in asthma cases over the last decade but it's likely one of a "huge mess of things," said Mary Rice, an instructor of medicine at Harvard University's Beth Israel Deaconess Medical Center.
"More doctors are aware of asthma, pollen seasons are longer, obesity, nutrition, diet, air pollution could be in the mix," Rice said. "Most studies suggest that [air pollution] contributes to the risk of asthma, but it's only one risk factor among many, many things that can contribute."
EPA acknowledges the recent research on air pollution triggers for asthma in the scientific documents underlying the rule, but the agency confined its benefits analysis to asthma attacks.
Industry, however, has accused the Obama administration and public health groups of overselling the ties between ozone pollution and asthma prevalence.
"Air quality has been increasing, pollution has been decreasing, things are getting better and asthma's getting worse," said Daniel Simmons, vice president for policy at the Institute for Energy Research (IER), a conservative think tank that's partly funded by the Koch brothers. "You have this disconnect."
The Texas Commission on Environmental Quality, one of EPA's biggest critics, has long questioned the agency's conclusions about asthma.
In its newsletter last October, the commission said it concluded that human volunteers exposed to ozone showed similar lung effects in asthmatics and in non-asthmatics, and that children were no more sensitive to ozone than young adults. The state pointed to increasing asthma admission rates in Texas as its proof.
"If asthma were actually tied to ozone, you would expect to see the instances of asthma decreasing, not increasing," the newsletter said. "In fact, data from Texas hospitals show that asthma admissions are actually highest in the winter, when ozone levels are the lowest."
The study by Johns Hopkins' Keets examined 23,065 children and found that race and income were risk factors for asthma, regardless of whether a child lived in an urban or rural area.
"Although the prevalence of asthma is high in some U.S. inner cities, it is equally high in some poor nonurban areas," the study found. "Taking the United States as a whole, living in an urban neighborhood is not associated with increased asthma prevalence."
The study was supported by EPA, the National Institute of Environmental Health Sciences, the National Institute of Allergy and Infectious Diseases and the National Cancer Institute.
Shortly after the study's publication in January, at least two opponents of EPA's proposal to tighten the national ozone standard touted its results as disproving EPA's claims about asthma.
In blog posts, IER and the Heartland Institute said the study showed that asthma prevalence was not higher in urban areas, where air pollution was typically more of a problem.
They argued that EPA's proposal, by imposing high compliance costs, could actually increase asthma prevalence by making people poorer.
"In light of this new evidence, EPA should rescind its proposed ozone rule," IER wrote. "This rule could exacerbate the public health problem it is trying to mitigate and impose enormous economic burdens on American families. Moreover, ozone levels are already declining without further regulation, obviating the need for more federal mandates."
Keet said such arguments are a "distortion" of her research team's findings.
In March, she wrote to EPA Administrator Gina McCarthy in an attempt to set the record straight. In her letter, she noted that the study did not examine air pollution and that living in an urban area should not be taken as a surrogate for high exposures to pollution.
"This study's finding has been misinterpreted by some who believe that it suggests that air pollution in general, and ozone in particular, is not important for asthma," she wrote. "This is an erroneous conclusion."
Still, the study was the subject of an intense exchange between in June between Rep. David McKinley (R-W.Va.) and Johns Hopkins University air pollution researcher Gregory Diette at a hearing of the House Energy and Commerce Committee.
Diette had been testifying that the science dictated that EPA set a lower ozone limit. McKinley -- whose son has asthma -- asked Diette to account for the Keet study.
"This report, Dr. Diette, from your Johns Hopkins institution, they have come out with a report themselves just recently and said they can't find a connection," McKinley said. "They say there is no statistical difference between the rates of asthma attacks in high-pollution areas than in non-pollution areas."
Diette shot back: "Just so it is clear, the conclusion of the study is not what you said it was."
As recently as last month, IER cited the study in a blog post that attempted to discredit the Obama administration's health claims used to justify the Clean Power Plan.
Simmons acknowledged that the authors of the study have disputed the group's interpretation of its results but said the findings still raised a "very important question" about the links between ozone and asthma.
"It looked at asthma in inner cities and asthma in the suburbs, and there was not a statistically meaningful difference," he said. "The inference that we drew from that is, don't you have more air pollution in inner cities than you do in the suburbs?"
Several researchers also suggested that industry is focusing on an area where the science is still unsettled -- what causes a person to have asthma -- and not on the part of the question where the science is more certain -- whether ozone increases the likelihood of attacks in people who already have asthma.
"The discussion of asthma going up is confusing the issue of the prevalence of asthma, meaning how many people develop the disease versus the disease course, so how sick the people who have asthma get," said Harvard's Rice, who was grilled about the asthma-ozone link by Rep. Jim Bridenstine (R-Okla.) at a recent hearing.
"At this point," Rice said, "there's very strong evidence to show that exposure to higher levels of ozone increases the risk of asthma attacks. I would say dozens, perhaps even hundreds of studies show that when ozone goes up, people who have asthma get sicker."
Some critics of EPA's scientific analysis argue, though, that there's also more uncertainty in the science linking asthma exacerbation and ozone than EPA is portraying.
"I don't think EPA fully takes into account uncertainties and other explanations for asthma exacerbations," said Julie Goodman, a principal at the consulting firm Gradient who has done ozone research for Texas and API. "Several things trigger asthma attacks, and it's very difficult to tease out what causes them in an epidemiology study."
Goodman is working on a paper that she said will prove the weight of evidence suggests the tighter standard won't have an impact on the number of asthma attacks.
"At certain exposure levels, ozone can exacerbate asthma. The question isn't whether it can," Goodman said. "The question is at what exposure level this happens and will lowering the standard have any additional health benefit. ... We conclude that the current standard is sufficient to protect public health."
'Something that resonates with anyone with a heart'
One area of agreement: Asthma is a powerful way to sell a new ozone standard, given how many Americans are affected by the disease.
Although ozone pollution has also been linked to premature death, Rice said focusing on asthma is a more real way to portray the dangers of ozone to humans.
"I think that as the risk of death goes up, it's harder for people to get their heads around than an asthma attack," Rice said.
EPA has also used asthma to attempt to coalesce support for its Clean Power Plan to reduce carbon dioxide emissions from existing power plants.
"We can all think of children with asthma and just how hopeless we feel. You see a child struggling and you want to help the child," IER's Simmons said. "So asthma is something that resonates with anyone with a heart."