In the sixties, smog clouded many U.S. skylines. Since the Clean Air Act of 1970 was enacted, a lot of that smog has disappeared. But now invisible pollution is the more important threat.

Ten years ago, the EPA issued a finding on the impact of carbon dioxide, methane and four other heat-trapping greenhouse gases:

Field: “What the endangerment finding basically says is that these six greenhouse gases endanger the health and welfare of people in the United States and around the world. And those risks are important enough that the source needs to be addressed through the Clean Air Act.”

That’s Chris Field of the Stanford Woods Institute for the Environment. He says the EPA’s finding is the foundation for federal regulations requiring improved vehicle fuel efficiency and clean power.

The Trump administration is trying to roll back these standards, but the scientific finding they’re based on remains.

Field: “It is 100% clear that the endangerment finding was justified in 2009, and now the evidence is totally overwhelming that in fact these greenhouse gases, through their effects on climate change, do endanger public health and welfare.”

Reporting credit: Daisy Simmons/ChavoBart Digital Media.
Photo credit: Alexander Popov / Unsplash