Of these, particles less than 2.5 micrometers in diameter, also known as fine particles or PM 2.5, pose the greatest risk to health. Fine particles are also the main cause of reduced visibility (haze) in parts of the United States, including many of our t
Particulate matter (PM) is one of the air pollutants regulated by the National Ambient Air Quality Standards (NAAQS). Reducing emissions of inhalable particles improves public health as well as visibility.