Scott Pruitt, President-elect Donald Trump's choice to lead the U.S. Environmental Protection Agency, questioned agency regulations governing exhaust emissions during a contentious Jan. 18 hearing before senators who will vote on his appointment.

Pruitt, Oklahoma's attorney general, said he disagrees with a waiver giving California the power to impose stricter standards than other states, and couldn't commit to keeping the decades-old waiver in place, reported the Los Angeles Times.

California regulators have used the waiver to cut greenhouse gas emissions by nearly a third since 2009, and more than a dozen other states have adopted the California standard to clean their own air.

Pruitt also said he would review the Jan. 13 decision by outgoing EPA Administrator Gina McCarthy to finalize fuel efficiency regulations through 2025, reported Automotive News.

The Obama administration set aggressive corporate average fuel economy standards as part of landmark 2012 legislation that gives the EPA until April of 2018 to decide whether to modify the 2022 to 2025 model year emission rules that would eventually require 50 miles per gallon across an automaker's fleet of models.