A reduction in air pollution since the early ’90s has saved the US at least $24 billion per year in costs associated with healthcare benefits for some Americans.

The study published in the American Economic Review last month looked at how efforts to reduce air pollution from 1993 to 2013 in the U.S. reduced the number of elderly deaths. This is the first study to examine the short-term impacts of particulate matter at this level.

The findings rely on about 40 billion data points, including daily pollution exposure for tens of millions of elderly people.