2024年6月20日 · Some particles less than 10 micrometers in diameter can get deep into your lungs and some may even get into your bloodstream. 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.

2023年7月11日 · PM is categorized based on its size, measured in micrometers (µm). The two most commonly discussed categories are PM2.5 and PM10. PM2.5 refers to particles with a diameter of 2.5 micrometers or smaller, while PM10 includes particles with a diameter of 10 micrometers or smaller.

PM2.5 refers to atmospheric particulate matter (PM) that have a diameter of less than 2.5 micrometers, which is about 3% the diameter of a human hair. Commonly written as PM 2.5, particles in this category are so small that they can only be seen with a microscope.

PM2.5 is used when describing pollutant levels both outdoor and indoor, where health impact from exposure considers amount of PM2.5 over a 24-hour period. Most studies indicate PM2.5 at or below 12 μg/m 3 is considered healthy with little to no risk from exposure.

2024年9月30日 · But PM 2.5, also known as fine particles, has the potential to penetrate deep into the lungs and contribute to health problems. PM 2.5 can enter indoor environments from outdoor sources such as vehicle emissions, industrial pollutants, and …

2024年7月16日 · Fine particles (PM 2.5) are the main cause of reduced visibility (haze) in parts of the United States, including many of our treasured national parks and wilderness areas. Learn more about visibility and haze. Particles can be carried over long distances by wind and then settle on ground or water.

2024年8月16日 · Using a nationwide network of monitoring sites, EPA has developed ambient air quality trends for particle pollution, also called Particulate Matter (PM). PM 2.5 describes fine inhalable particles, with diameters that are generally 2.5 micrometers and smaller.