Assume that a particle has a diameter of 10 µm: how much more mass does it bring to the airway than a 1 µm particle?
The volume of a globular particle is 4/3×π×r³, i.e. proportional to radius (r) cubed. Thus a 10 µm particle has a mass which is 1000 times as large as that of a 1 µm particle.