Particulate matter is one of the most complicated forms of air pollution. Unlike its air pollutant counterparts, particulate matter doesn’t come from a singular source, nor does it include a particular chemical or gas.
Rather, particulate matter is an amalgamation of different particles, both solid and liquid, that behave in similar ways and are of similar size. Particulate matter is further subdivided into different categories based on particle size.
But, what are the differences between these particle size categories? Why separate particle matter into these particle sizes? We wanted to address these questions in this article.
What Are the Different Categories of Particulate Matter?
Particulate matter is separated into three main groupings: coarse particles (PM10), fine dust (PM2.5), and ultrafine dust (PM0.1). These particle sizes, in general, differ in origin and health effects.
Coarse Particles (PM10)
Our first entry on this list is the largest particle size we will be discussing: PM10. Also known as coarse particles, PM10 is a grouping of particles with an average diameter of 10 μm or smaller. Some common examples of PM10 are:
- Mold spores
- Airborne viral particles
Because PM10 includes any particles smaller than 10 μm in diameter, PM10 also contains fine dust (PM2.5) and ultrafine dust (PM0.1), though we usually think of ‘coarse particles’ as the range of particle size between 2.5 and 10 μm. The last few examples from the list above are also included in PM2.5.
Coarse particles, while not as dangerous as fine or ultrafine dust, can still pose a significant health threat. These particles can penetrate into our lungs and irritate your airways, nose, throat, and eyes. PM10 is usually created directly, with sources like construction work, road dust, or natural dust storms, rather than secondary, atmospheric sources.
For a complete breakdown of PM10, we recommend you check out our article: PM10: How Do Coarse Particles Affect Air Quality?
Fine Dust (PM2.5)
The next grouping we will discuss in fine dust, arguably the most well-known type of particulate matter. PM2.5 is a grouping of particles with an average diameter of 2.5 μm or less, capable of penetrating deep into our lungs and even entering our bloodstream.
Fine dust can come from natural or human-made sources, like:
- Vehicle exhaust
- Power plant emissions
- Other combustion activities
Like PM10, PM2.5 also contains ultrafine dust (PM0.1), but when we refer to fine dust, we are usually talking about the range between 0.1 and 2.5 μm.
Ultrafine Dust (PM0.1)
The final type of particulate matter we will address is ultrafine dust. PM0.1 is even smaller than fine dust, with an average particle size of 0.1 μm or smaller, and originates from similar sources as PM2.5.
Less is known about PM0.1 than PM2.5, or even PM10, but there is a growing body of research indicating that ultrafine dust poses a worse threat than PM2.5, as the smaller particle size can infiltrate our bodies to an even greater extent. Recent studies show that PM0.1 displays enhanced cardiovascular toxicity and greater potential for oxidative stress. Ultrafine particles also represent the majority of airborne particulate matter indoors (up to 90%).
Overall, ultrafine dust is not to be taken likely, and additional research will shed light on the further differences between it and PM2.5.
As both an indoor and outdoor air pollutant, particulate matter, including PM10, PM2.5, and PM0.1, is a complex and significant health threat. To learn more about particulate matter, check out our comprehensive guide below: