- Perspectives -

Beyond the numbers: the uncomfortable complexity of PM2.5

by Siriel Saladin on January 28, 2025

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.

Compared to CO2, temperature or humidity, the concept of PM2.5 is far more complex and involves inevitable limitations that go beyond measurement uncertainties. In other words, the error stated by a monitor (whether high or low-cost) might be much smaller than the “real” error caused by making the wrong assumptions about PM2.5 - not just regarding size!

Once we understood this, it led us to some interesting follow-up questions, for example: How accurately can the health risk from airborne particles be monitored? And how accurate does it need to be?

At AirGradient, we have decided to dig deeper and kick off a series of blog articles. It will explore hidden dilemmas, provide surprising insights, and ask uncomfortable questions. Issue 1 will be published alongside this issue and can be found here, sharing microscopic impressions and demonstrating how PM2.5 is an umbrella term for a large variety of particles.

Do you have questions in mind that you would like to learn about in prospective articles? Let us know!

Our current questions:

  • What is PM2.5?
  • Why PM2.5 and not, for example, PM3?
  • Why is PM2.5 a health issue?
  • Is PM2.5 always a health issue?
  • How scientifically founded is the PM2.5 guidance from WHO?
  • How accurately can we measure PM2.5 (even with the best technology)?
  • Is there a better metric than PM2.5?

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