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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 is it a single 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.
Wildfires, like the recent California wildfires, are a natural source of particulate matter.
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 particles (PM2.5), and ultrafine particles (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 defined as all particles with an aerodynamic diameter of 10 μm or smaller. Some common examples of PM10 are:
- Mold spores
- Bacteria
- Dust
- Smoke
- Airborne viral particles
Because PM10 includes any particles smaller than 10 μm in diameter, PM10 also contains fine particles (PM2.5) and ultrafine particles (PM0.1), though we usually think of a coarse range of particle sizes 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 Particles (PM2.5)
The next grouping we will discuss is fine particles, arguably the most well-known type of particulate matter. PM2.5 is a grouping of particles with an aerodynamic diameter of 2.5 μm or less, capable of penetrating deep into our lungs and even entering our bloodstream.
Fine particles can come from natural or human-made sources, like:
- Vehicle exhaust
- Wildfires
- Power plant emissions
- Other combustion activities
Ultrafine Particles (PM0.1)
The final type of particulate matter we will address is ultrafine dust. PM0.1 is even smaller than fine dust, with an aerodynamic 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 lightly, 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 and other common indoor air pollutants, download our free eBook, Indoor Air Quality 101 below. We’ll run through the key concepts you need to know to understand air quality, and how to start planning your monitoring and improvement strategy:
