We don’t have the details of the new policy. But don’t be fooled by this talk of transparency. He and some conservative members of Congress are setting up a nonexistent problem in order to prevent the E.P.A. from using the best available science. These studies adhere to all professional standards and meet every expectation of the scientific community in terms of peer review and scientific integrity. In the case of the air pollution studies, a rigorous follow-up examination was done by the Health Effects Institute, a nonprofit research group that studies air pollution. The institute corroborated the findings.

In taking this action, Mr. Pruitt appears to be adopting the policies of the Honest and Open New E.P.A. Science Treatment Act, a bill aimed at the agency. Conservative lawmakers have tried to pass versions of this bill before to shackle the agency’s rule making. That law would prohibit the E.P.A. from taking any action “unless all scientific and technical information relied on to support” it is “specifically identified, and publicly available in a manner sufficient for independent analysis and substantial reproduction of research results.”

An analysis of a similar bill introduced in 2015 by the Congressional Budget Office estimated it would cost $250 million a year over the first few years to carry out because it would require new “data collection, correspondence and coordination with study authors, construction of a database to house necessary information, and public dissemination” of the information.

The analysis, which did not appear to take into account the cost of redacting details like trade secrets or personally identifiable medical information, also predicted the agency would reduce by half the number of studies it relies on in developing policies and regulations because of the cost of complying with the law.

“The quality of the agency’s work would be compromised if that work relies on a significantly smaller collection of scientific studies,” the analysis found.

This approach would undermine the nation’s scientific credibility. And should Mr. Pruitt reconsider regulations now in place, this new policy could be a catalyst for the unraveling of existing public health protections if the studies used to justify them could no longer be used by E.P.A.