Interpreting atmospheric pollen counts for use in clinical allergy: spatial variability.
BACKGROUND
Atmospheric pollen counts are ubiquitous data, however, few guidelines exist for interpreting them. A fundamental problem involves appreciating spatial variability in atmospheric pollen concentrations, for example, differences in pollen conditions between neighborhoods within a metropolitan area. The significance of this problem is perhaps most manifest in clinical allergy where pollen counts from a single rooftop pollen sampler are often applied to an entire city.


OBJECTIVE
This review will consider experimental data concerning spatial variability in atmospheric pollen concentrations. Several guidelines for interpreting pollen counts with respect to this spatial variability will be presented.


METHODS
This review will consider three independent bodies of literature concerning spatial variability in atmospheric pollen concentrations: (1) controlled-release experiments, (2) the paleoecology literature, and (3) atmospheric surveys.


RESULTS
Four principal results emerged. First, pollen concentrations in the atmosphere appear to be inherently heterogeneous. Differences in pollen recovery between adjacent points increase in a predictable manner as a function of distance. Second, spatial variability decreases as the distance between pollen sources and destination regions increases. Pollen recovery across a city is most similar when pollen is transported from distant source regions. Third, the size of the source area represented by a pollen sampler depends on the distance between the sampler and the nearest vegetation. Samplers located near vegetation reflect small source areas; source areas expand considerably when the distance to the nearest vegetation increases. Last, individual pollen types travel characteristic distances from their source. Heavy pollen types collected at a particular point reflect a smaller source areas than lighter types which represent much larger source areas.


CONCLUSIONS
These conclusions allow allergists to interpret their atmospheric pollen counts with greater sophistication than was previously possible. Mathematical equations presented in this review permit rough calculations concerning source areas.
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Multidata LLC, St. Louis Park, Minnesota 55416-5702, USA.
D000397:Air Pollution / Q000032:analysis*; D002452:Cell Count; D004739:England; D006801:Humans; D006967:Hypersensitivity / Q000517:prevention & control*; D008910:Minnesota; D009518:New York; D010162:Paleography; D011058:Pollen / Q000166:cytology*