PM2.5 and PM10 are the two types of air pollution that the WHO estimates affect “more people than any other pollutant,” but they are different. Here’s how the two contrast.
PM2.5 Meaning
PM2.5 (Particulate Matter 2.5): “PM” refers to particulate matter—particles in the air. PM2.5 are tiny airborne particles with a diameter of 2.5 micrometers or smaller. PM2.5 particles can stay suspended in the air for a long time and are small enough to be inhaled deep into your lungs. They can come from vehicle emissions, industrial processes, and even natural sources like dust and pollen.
PM10 Meaning
PM10 (Particulate Matter 10): These are slightly larger particles with a diameter of 10 micrometers or smaller. While larger than PM2.5, they are still very small and can also be inhaled into your lungs. PM10 particles come from sources similar to PM2.5, including dust, vehicle emissions, and industrial activities.
PM2.5 vs. PM10
The difference between PM10 and PM2.5 is size. Those particles are things like organic dust, airborne bacteria, construction dust, and coal particles from power plants.
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Does Size Matter?
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.)
WHO Air Quality Guidelines for PM2.5 and PM10 Safe Levels
| Particulate Matter | 24 hr limit (µg/m³) | Annual limit (µg/m³) |
| WHO PM2.5 (µg/m³)* | 15 | 5 |
| WHO PM10 (µg/m³) | 45 | 15 |
What PM10 and PM2.5 Are Not VOCs
Finally, it’s helpful to think of what PM is not. Particulate pollution does not include gas pollutants like ozone and NO2. It also doesn’t include gas pollutants that often come from inside our home, such as formaldehyde off-gassing from new furniture.
Bottom Line: Differences Between PM2.5 and PM10?
PM stands for ‘particulate matter’. PM10 is particles 10 microns and below. PM2.5 is 2.5 microns and below. PM does not include gas pollutants like ozone and NO2.
Breathe safe!
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