Today, the Environmental Protection Agency (EPA) announced it’s rescinding the 2009 “endangerment finding” that labeled carbon dioxide a pollutant harmful to human health. EPA Administrator Lee Zeldin broke the news on the Ruthless Podcast ahead of the formal announcement. 

Zeldin explained his agency’s rationale for the rule change like this: “The Obama administration said that carbon dioxide, when mixed with a bunch of other well-mixed gasses, greenhouse gasses, that it contributes to climate change. How much? They don’t say … they say that climate change engenders human health, so because of these different mental leaps … then there were all sorts of vehicle regulations that followed.” 

This announcement didn’t come out of thin air. Back in March 2025, the EPA announced it would formally reconsider the 16-year-old regulation. Zeldin added that undoing this regulation is akin to “basically driving a dagger into the heart of the climate change religion.” 

The EPA will first tackle the endangerment finding with respect to vehicular emissions stemming from the Massachusetts v. EPA (2007) decision. E&E News adds the rule change will specifically tackle legal arguments from the 2009 rule, not “the science of climate change.”

The 2009 endangerment finding was born out of the 2007 Supreme Court decision, Massachusetts v. EPA. The 2007 ruling found greenhouse gases, like carbon dioxide (CO2), to be pollutants that harm human health and welfare under Section 202(a) of the Clean Air Act. The decision influenced the 2009 Obama-era rule to regulate greenhouse gas emissions on gas-powered vehicles. It was then broadly applied by the Obama and Biden EPAs to regulate power plants and other industries deemed to be emitting harmful greenhouse gases. The original rule was published in December 2009 and defined the endangerment finding as follows: 

  • Endangerment Finding: The Administrator finds that the current and projected concentrations of the six key well-mixed greenhouse gases—carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6)—in the atmosphere threaten the public health and welfare of current and future generations.
  • Cause or Contribute Finding: The Administrator finds that the combined emissions of these well-mixed greenhouse gases from new motor vehicles and new motor vehicle engines contribute to the greenhouse gas pollution that threatens public health and welfare.

Since the endangerment finding is an agency rule and not a formal law adopted by Congress, it can be repealed by the Trump EPA. The agency will first initiate a formal reconsideration process, as it did in March 2025, to re-evaluate the rule by considering new scientific data and public comments. Alongside this, the agency will issue a “justification for reversal” explaining their policy change. The rule change is expected to be challenged in the courts by environmental groups who want this rule left in place.

Our Center for Energy and Conservation will continue to monitor updates on this rule change.