Definition:
These are tiny fragments of pollen that are dispersed into the air like an aerosol when larger intact pollen grains rupture.
For those with a severe allergy to pollen or with asthma that is triggered by pollen, sub-pollen particles (SPP's) should be of concern.
Whole pollen grains are only able to reach the upper
airways through the eyes, nose, and mouth, triggering the symptoms of "rhinitis" or hay fever. These particles are
usually filtered out in the form of coughing, sneezing, and
watery eyes.
SPP's, however, are respirable particles that can easily deposit in the lower airways, triggering allergic inflammation and attacks with those who suffer from severe pollen allergies and asthma.
Particle Size:
Average of 4 microns and below. Can be as small as .3 microns. The forget-me-not produces the smallest intact pollen grains that are extremely minute particles only .006 microns in size. SPP's from ragweed, one of the most widespread and common triggers for those with pollen allergies, typically range from .5 - 4 microns.