The 2009 Endangerment Finding by the EPA Administrator on December 7, 2009, included two main determinations. The first found that the current and projected concentrations of six key greenhouse gases, including carbon dioxide (CO2), in the atmosphere threaten the public health and welfare of current and future generations. The second, the “Cause or Contribute Finding,” determined that combined emissions of these gases from new motor vehicles and engines contribute to this threat EPA. “Air pollution” was defined as the collective mix of these six greenhouse gases. The term “public welfare” under the Clean Air Act was interpreted to include effects on various environmental factors. The finding was published in the Federal Register on December 15, 2009.
The finding was utterly dependent upon a political definition of welfare. It was unsound and was essentially junk science for a political cause. For human health directly the effects were plain wrong or grossly exaggerated.
A doubling of atmospheric CO2 levels from around 400 ppm to 1000 ppm, with oxygen content remaining unchanged, would likely have minimal direct acute health impacts on most healthy adults, as this concentration is commonly encountered in indoor environments without widespread reports of severe symptoms. Traditional occupational safety guidelines, such as those from OSHA, set permissible exposure limits at 5000 ppm for an 8-hour workday, indicating that 1000 ppm is well below thresholds for immediate toxicity or asphyxiation. At this level, some individuals might experience subtle effects like mild drowsiness or slight increases in heart rate and blood pressure, but these are not universal and often depend on factors such as duration of exposure, ventilation, and individual sensitivity.
On February 12, 2026, the EPA under the Trump administration finalized a rule to withdraw the 2009 Greenhouse Gas Endangerment Finding.
What was withdrawn: The 2009 “Endangerment Finding” (and related Cause or Contribute Finding), which concluded that the current and projected concentrations of six key greenhouse gases in the atmosphere threaten the public health and welfare of current and future generations.
Significance: This finding was the legal bedrock that allowed the EPA to regulate emissions
from motor vehicles, power plants, and other industrial sources.
Reason for Withdrawal: The EPA stated that the 2009 analysis was “flawed,” “too pessimistic,” and did not properly analyze the scientific record. The administration argued that greenhouse gases do not pose a direct threat to public health in the way conventional air pollutants (like smog) do.
Good riddance.
The k2p blog 