Did Cryptic Invasion of North America by Common Reed Change Exposure to Pollen Allergens?

Abstract

Common reed, Phragmites australis (reed), is a very tall grass that spread greatly to occupy large areas near many eastern North American cities over the past century. Its aerially dispersed pollen is known to incite allergic reactions, and possibly asthma, in some persons, but is not distinguished from that of any other grass in routine pollen monitoring. We hypothesize that this regional expansion by reed has increased late-season exposure to grass-pollen allergens in parts of these metropolitan areas. The information available indicates that reed's geographic location, high abundance, small pollen size, release of pollen relatively far above ground, substantial pollen productivity, pollen allergen composition, and late season of pollen release all point to its potential importance for a large number of persons whose health may be degraded by grass pollen. If the other common late-flowering grasses in the same area have larger pollen grains, it may be possible to visually distinguish reed pollen captured by monitoring devices. If not, ratios of stable isotopes of carbon in the pollen may permit differentiation. Otherwise, analytical techniques based on molecular differences need further development in order to estimate local population exposure to allergens from reed. Some 90 million North Americans may live close enough to large tracts of reed to be exposed to substantial concentrations of its pollen, so much more attention to this situation seems warranted. If reed pollen were found to be a health hazard for a particular metropolitan area, removal of the pollen sources may be more feasible than is the case for many other species.