The University of Chicago says in a study that based on daily data from more than 200 monitors across China from 2013 to 2017, the analysis found that cities have cut levels of PM 2.5 - the tiny airborne particles considered most harmful to health - by an average of 32 percent in just four years.
PM 2.5 can play a role in heart disease, stroke, and lung ailments such as emphysema and cancer.
"We don't have a historical example of a country achieving such rapid reductions in air pollution. It's remarkable," said Michael Greenstone, the economist and director of the Energy Policy Institute at the University of Chicago, who conducted the studies.
By contrast, it took the United States 12 years and a severe recession to attain similar improvements in air quality after it enacted its 1970 Clean Air Act, he noted.
"China's not held up as a democratic regime, and yet here we have a clear example of the public demanding something and the government delivering it," said Greenstone.
Yet the war on smog has come with social costs. To clear the skies, authorities ordered thousands of polluting factories to leave urban centers, displacing hundreds of thousands of immigrants.