Congressional Republicans are already pressing Environmental Protection Agency assistant administrator Gina McCarthy, President Obama’s pick for the agency’s new administrator, on the EPA’s use of secret data to formulate air quality rules.

“EPA has continually refused to make public the basic scientific data underlying virtually all of the Agency’s claimed benefits from new Clean Air Act (CAA) rules,” wrote Texas Republican Rep. Lamar Smith and Louisiana Republican Sen. David Vitter in a letter to McCarthy. “Everyone agrees on the importance of clean air, but EPA needs to release the secret data they use in formulating new rules.”

Smith and Vitter specifically pointed to the lack of transparency behind the EPA’s forthcoming review of National Ambient Air Quality Standards for ozone.