AirGradient Forum

Beyond the numbers: the uncomfortable complexity of PM<sub>2.5</sub>

AirGradient Blog
#1

We all know PM2.5 is a major contributor to air pollution causing severe health damage around the globe. But do you know what PM2.5 actually means? You would be surprised to learn that there is no clear numerical answer to the total mass of airborne particles smaller than a certain size, e.g. 2.5 micrometers.

This is a companion discussion topic for the original entry at https://www.airgradient.com/blog/the-complexity-of-pm25/
#2

Two questions we often get: “how long does PM2.5 stay inside your body”, and “can you body expell PM once inhaled, or does it stay inside your body forever”? Would you be able to shed some light on the long-term health impact of inhaling PM?

Thanks for the great work!

#3
#4

Thanks for the question. The answer depends on the type of particles.

1) Do particles stay in your body forever?

Some are removed quickly, others can stay for a long time.

2) What happens after you inhale PM?

Water-soluble particles (e.g. salt from the sea, or ammonium sulfate from farming)

  • Dissolve in the lungs within minutes
  • Enter the bloodstream
  • Treated like substances taken up via food or water
  • Once dissolved, these compounds can interact with our cells (in a good or bad way, based on what they are)

Water-insoluble particles (e.g. soot, dust, asbestos)

  • Do not dissolve easily
  • The body tries to remove them by:
    • mucocilliary escalator that pushes the particles upwards out of the lungs (see linked video in article above)
    • immune cells that “eat” particles
  • Removal depends a lot on PM type and size

Takeaway

Our bodies can remove many particles, but these defence mechanisms can be overwhelmed. When that happens, particles build up, leading to chronic inflammation and, over time, disease.

The risk of this happening depends on:

  • Toxicity (how harmful the particle is)
  • Size (smaller particles can reach deeper into the lungs)
  • Exposure (how many particles you breath in for how long)

Triangle of death: the more extreme any of these factors, the higher the chance of harm.

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