The effect of height on pollen concentration is not well documented and
little is known about the near-ground vertical profile of airborne
pollen. This is important as most measuring stations are on roofs, but
patient exposure is at ground level. Our study used a big data approach
to estimate the near-ground vertical profile of pollen concentrations
based on a global study of paired stations located at different heights.
We analyzed paired sampling stations located at different heights
between 1.5 and 50 m above ground level (AGL). This provided pollen data
from 59 Hirst-type volumetric traps from 25 different areas, mainly in
Europe, but also covering North America and Australia, resulting in
about 2,000,000 daily pollen concentrations analyzed. The daily ratio of
the amounts of pollen from different heights per location was used, and
the values of the lower station were divided by the higher station. The
lower station of paired traps recorded more pollen than the higher
trap. However, while the effect of height on pollen concentration was
clear, it was also limited (average ratio 1.3, range 0.7–2.2). The
standard deviation of the pollen ratio was highly variable when the
lower station was located close to the ground level (below 10 m AGL). We
show that pollen concentrations measured at >10 m are representative
for background near-ground levels.