What’s the Difference Between PM2.5 and PM10?

PM10 versus PM2.5 particle size

The difference between PM10 and PM2.5 is size. “PM” refers to particulate matter—particles in the air. Those particles are things like organic dust, airborne bacteria, construction dust, and coal particles from power plants (here’s what researchers in Shanghai found when they collected air pollution particles and found out what they were made of). 

Size Matters

Now on to size. The “10” and the “2.5” refer to microns (AKA micrometers). Microns are tiny. Here’s an idea of how small microns are compared to human hair:

Next there’s a hidden (unlabelled) detail in the terms “PM10” and “PM2.5.” That is the “smaller than” piece. Each pollutant type is defined as that size and below. So PM10 is particles 10 microns and below. PM2.5 is 2.5 microns and below. (That means PM10 includes PM2.5.)
Particle Sizes PM10 vs PM2.5 Pollution

 

What PM Is Not

Finally, it’s helpful to think of what PM is not. Particulate pollution does not include gas pollutants like ozone and NO2.

 

Related image

Learn More About PM2.5

  1. I describe how governments measure PM2.5 (including the trick of how they get rid of any particles in the air larger than 2.5 microns)
  2. Here I describe the latest science on what PM2.5 does to our bodies.
  3. In this answer, I detect PM2.5 in my home in Beijing and test whether a simple DIY air purifier I made can clean it up.

Bottom Line: What's the difference between PM2.5 and PM10?

PM10 is particles 10 microns and below. PM2.5 is 2.5 microns and below. (That means PM10 includes PM2.5.)

PM does not include gas pollutants like ozone and NO2.

Breathe safe!


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