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.

2025年3月20日 · EPA is setting the level of the primary (health-based) annual PM 2.5 standard at 9.0 micrograms per cubic meter to provide increased public health protection, consistent with the available health science.

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.

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.

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8月15日 · The EPA’s revision of the PM 2.5 standards is a crucial step in reducing these health risks. What Has Changed? As of February 2024, the EPA has strengthened the primary (health-based) annual PM 2.5 standard, lowering the …