PM2.5和其他类型的微粒是一个“热门话题”。从维基百科的微粒;大小、形状和溶解性物质)(https://en.wikipedia.org/wiki/Particulates大小,_shape_and_solubility_matter): > […]10-micrometer大小并不代表一个严格的呼吸道和non-respirable粒子之间的界限,但已经约定了空气颗粒物的监测监管机构。因为他们的体积小,* * 10微米或更小的粒子(粗颗粒物PM10) * *可以穿透的最深的部分肺细支气管或肺泡等;当哮喘患者暴露于这些条件就会引发支气管收缩。>同样,所谓的细颗粒物(PM2.5),往往渗透到肺的气体交换区域(肺泡),和非常小的粒子(超细颗粒物,PM0.1)可能会通过肺部影响其他器官。渗透的粒子不是完全依赖它们的大小;形状和化学成分也有一定作用。为了避免这种并发症,简单的术语是用来表示不同程度的点粒子的相对渗透到心血管系统。 Inhalable particles penetrate no further than the bronchi as they are filtered out by the cilia. Thoracic particles can penetrate right into terminal bronchioles whereas PM0.1, which can penetrate to alveoli, the gas exchange area, and hence the circulatory system are termed respirable particles. In analogy, the inhalable dust fraction is the fraction of dust entering nose and mouth which may be deposited anywhere in the respiratory tract. The thoracic fraction is the fraction that enters the thorax and is deposited within the lung's airways. The respirable fraction is what is deposited in the gas exchange regions (alveoli). >The smallest particles, less than 100 nanometers (nanoparticles), may be even more damaging to the cardiovascular system. Nanoparticles can pass through cell membranes and migrate into other organs, including the brain. Particles emitted from modern diesel engines (commonly referred to as Diesel Particulate Matter, or DPM) **are typically in the size range of 100 nanometers (0.1 micrometer).** [...] ---- From AirNow.gov's [Particle Pollution (PM)](https://airnow.gov/index.cfm?action=aqibasics.particle): > - **Coarse dust particles (PM10) are 2.5 to 10 micrometers in diameter**. Sources include crushing or grinding operations and dust stirred up by vehicles on roads. > - **Fine particles (PM2.5) are 2.5 micrometers in diameter or smaller**, and can only be seen with an electron microscope. Fine particles are produced from all types of combustion, including motor vehicles, power plants, residential wood burning, forest fires, agricultural burning, and some industrial processes However, EPA.gov's [Particulate Matter (PM) Basics; What is PM, and how does it get into the air?](https://www.epa.gov/pm-pollution/particulate-matter-pm-basics#PM) says: > - **PM10:** inhalable particles, with diameters that are **generally 10 micrometers and smaller**; and > - **PM2.5:** fine inhalable particles, with diameters that are **generally 2.5 micrometers and smaller.** When discussing "PM2.5", is there any standardized understanding of which particles are or are not included? Is it everything that's 2.5 microns and smaller? Or Everything *between* 2.5 and 0.1 microns? Likewise does PM10 include all of PM2.5? And by what method is "size" specified? Is this an aerodynamic size from some kind of inertial impactor configuration (virtual or real), or an optical size from scattering, or something else?