Scott Pruitt’s proposed “secret science” rule could be one of the most consequential actions taken by the EPA administrator since sweeping into the agency with a stunning agenda to deconstruct key safeguards on the environment, according to his critics and supporters.

The rule announced Tuesday could require agency officials to omit credible studies that scientists say justify limits on air pollution. As Pruitt’s adversaries gaped at what they described as an audacious attack on environmental rulemaking, some of his ardent supporters applauded the administrator for boldly addressing what they see as liberal bias in scientific circles.

Joseph Bast, CEO of the conservative Heartland Institute, which rejects mainstream climate science, called it the “most consequential decision made by EPA since the election of Donald Trump.”

The move is seen as a sweeping change in part because the studies being targeted tend to focus on the health impacts of conventional air pollution, like smog. Reducing those effects on people can amount to billions of dollars in avoided health costs, which helps justify EPA rules to clean up power plants in addressing climate change.

Major regulations, including the Clean Power Plan, rely on dozens of studies. Many of those include personal health information, which researchers are not willing or able to release. Pruitt’s rule focuses on the kind of research that relies on private databases.

Researchers say they’re not sure what specific studies could be affected by the rule because Pruitt’s proposal is indeterminate. It appears to give leeway to industry research, they said. It would also allow Pruitt or his successor to “exempt significant regulatory decisions on a case-by-case basis if he or she determines that compliance is impracticable because it is not feasible,” according to the proposed rule.

Some older studies that didn’t find a link between air pollution and human health may also be precluded, said Dan Greenbaum of the Health Effects Institute. An example is a recent EPA decision not to tighten air quality standards for nitrogen dioxide, a decision supported by research that didn’t find causation.

“Overall, this language is still pretty vague, and exactly what will and won’t be allowed is not clear,” Greenbaum said.

Researchers and legal experts who read the proposed rule closely say it’s hard to predict which research will be targeted. Nonetheless, here are some possible targets for exclusion.

Harvard ‘Six Cities’ study

This 1993 study has influenced federal air pollution regulations and laws. It’s also been attacked by industry and its allies ever since it was released.

It tracked more than 20,000 people in six American cities for two years and connected air pollution to serious health effects, including mortality. It found that people in dirtier cities died faster than those in clean cities. The study’s findings were independently verified, and it has been used as part of the Clean Air Act.

The Congressional Budget Office estimated benefits of $20 billion to $170 billion per year due to reduction of fine particulate matter, which the study first connected to mortality. Because the study uses private health data, which researchers have refused to make public, it might not be eligible for use in future EPA regulations under Pruitt’s plan. The study was instrumental in the crafting of the national ambient air quality standards in 1997, which added a category for fine particulate matter.

Pruitt’s proposed rule was crafted with the Harvard study in mind. Steve Milloy, a former coal executive and Trump EPA transition team member, was instrumental in pushing the proposed rule and has repeatedly criticized the Harvard study.

1995 American Cancer Society study

Another groundbreaking body of research, this study found a link between air pollution and cardiovascular disease, respiratory disease and lung cancer. It has been used in regulations over the years and has been attacked by industry. The American Cancer Society study has been backed up by dozens of independent studies that found similar results.

Arden Pope, an economics professor at Brigham Young University and co-author of the study, said researchers can’t disclose all of their data when human subjects are involved. Institutions typically require researchers to agree to an Institutional Review Board, or IRB, that guarantees data privacy in any study with medical records, where blood is drawn and where sensitive health information is recorded.

“You have an ethical and institutional obligation to maintain the confidentiality of that data,” Pope said. “And then some people might say, ’But ah, all you have to do is take off the names and de-identify it,’ but in most cases, your IRB won’t let you get away with this.”

He said the research has been replicated already and that it has been public for years.

“Look at where we publish these results. They’re all getting published in very high-quality, peer-reviewed journals; it’s hardly secret,” Pope said.

‘Air Pollution and Mortality in the Medicare Population’

This major study, published in 2017 found that levels of air pollution permitted by EPA killed thousands of people every year. African-Americans and the poor are disproportionately affected by air pollution, it found. Reducing fine particulate pollution, even slightly, would save the lives of 12,000 people annually, the study says.

“The study showed that black men and persons eligible to receive Medicaid had a much higher risk of death associated with exposure to air pollution than other subgroups,” the researchers wrote. “These findings suggest that lowering the annual NAAQS may produce important public health benefits overall, especially among self-identified racial minorities and people with low income.”

The groundbreaking study may or may not be blocked under the proposed rule, said Greenbaum of the Health Effects Institute, which funded the research. It relies on health data from 60 million Medicare patients from 2002 to 2012; the researchers are making their codes and methodology available.

Under Pruitt’s proposed rule, the study may not be used in the formation of future air pollution regulations, which have to be updated under the Clean Air Act every few years.

Reprinted from Climatewire with permission from E&E News. E&E provides daily coverage of essential energy and environmental news at