In the United States, annual average levels of fine particulate matter—PM2.5, a measure of solid particles and liquid droplets that are 2.5 micrometers or smaller found in the air—declined 24 percent from 2009 to 2016, then increased 5 percent between 2016 to 2018.
Click here for original story, Air quality has worsened since 2016, associated with more premature deaths in U.S.
Source: Phys.org