While monitoring air quality, scientists traditionally relied on mass concentration to measure particulate matter (PM). This metric tells you the total mass of particles per unit volume of air. But for sub-micron particles – those less than one micrometer in diameter – mass concentration falls short. Here’s why measuring particle number by size distribution is a superior approach.
The Small Matter of Small Particles
Sub-micron particles are incredibly tiny. Imagine a human hair – typically around 70 microns thick. A sub-micron particle is hundreds to thousands of times smaller! Due to their miniscule mass, even large numbers of sub-micron particles can register a low mass concentration. This can be misleading, as the health risks they pose aren’t dependent solely on weight.
Penetrating Deep: Size Matters More
Sub-micron particles, especially those in the ultrafine range (less than 100 nanometers), are deeply concerning. Their small size allows them to bypass the body’s natural defenses and infiltrate deep into the lungs. These particles can even enter the bloodstream, potentially causing respiratory and cardiovascular problems.
See The Air 