By Chris Adams

More than four decades after becoming law, the Clean Air Act has helped reduce smog and pollution in the skies over American cities. But now, given the policy preferences of GOP leaders who control the White House and Congress, the law and related regulations are being scaled back.

John Walke (bio, Twitter), director of the clean air program at the environmental advocacy organization Natural Resources Defense Council, led National Press Foundation fellows through an explanation of the Clean Air Act and related regulations.

Congress set the basic structure of the act in the 1970s and updated it in 1977 and 1990. It requires the U.S. Environmental Protection Agency to set national ambient air quality standards for common pollutants: particulate matter, ozone, sulfur dioxide, nitrogen dioxide, carbon monoxide and lead.

As of mid-2017, he said, there are multiple bills in Congress that would scale back one of the linchpins of the act: the fact that air quality regulations must be based on health science – not economic factors or other feasibility standards. (Whether those bills could clear a filibuster in the U.S. Senate is unclear.)

So far under President Donald Trump and EPA Administrator Scott Pruitt, Walke said the administration is looking to reverse several clean air regulations. In a previous blog post on the Trump administration’s EPA budget, he called the potential “the most extreme and reckless budget attack on the enforcement of clean air, clean water and environmental protections in the nation’s history.”