How wildfire smoke is erasing years of progress toward cleaning up America's air

Smoky haze from wildfires in Canada obscures New York City's Empire State Building this year. The air in the U.S. has improved over the past 50 years, but smoke pollution from growing wildfires erodes much of that progress. (David Dee Delgado/Getty Images)

Over the last few decades, air in the U.S. has undergone a remarkable transformation: pollution levels of health-damaging tiny particles have dropped by roughly 40% since 2000, primarily thanks to the country's decades-long effort to improve air quality through the Clean Air Act, a landmark environmental law.

Smoke from wildfires fueled by human-driven climate change, however, has erased roughly 25% of those air quality gains, according to a new study published Wednesday in Nature. "We've seen really remarkable improvements in air quality," says Marissa Childs, one of the authors of the study and a researcher at Harvard's Center for the Environment. "But wildfire smoke is undoing that progress in many states."