EPA chief Zeldin announced plans to rescind the U.S.'s biggest tool to fight climate change in an Indy visit. Environmentalists call it a direct assault.

What is the agency actually proposing? In 2009, the EPA reached what is known as the “endangerment finding” — a determination that greenhouse gases are dangerous to human health because of their role in climate change, on which the agency’s efforts to regulate greenhouse gas emissions rests. Now, the EPA proposes rolling back that finding.

The endangerment finding underpins the EPA’s ability to regulate greenhouse gases. The Trump administration is trying to reverse it.