Spatial variability of airborne pollen across New York City

Background/Question/Methods

In the New York City (NYC) region, airborne pollen is abundant mainly from the beginning of March through the end of October. 15 years of daily air sampling using a volumetric Burkard Spore Trap have shown that each pollen taxon will typically appear, rise to a peak and then decline at a characteristic time each year. However, little is known about how the amount of pollen or its taxonomic composition varies across the region. The question is of public health interest since many of these pollen types are clinically significant allergens with known sensitization patterns. For the fall 2012 pollen season (August to October), we asked if there is spatial variation in the ragweed (Ambrosia sp.) pollen deposition at sites across 4 of NYC’s 5 boroughs. We deployed 10 modified Tauber Traps (non-volumetric passive samplers) on light poles at 2.5 meters above street level, a height relevant to human health, chosen from sites included in the NYC Community Air Survey. Five sites had land use features indicative of ragweed habitat; five more had characteristics inhospitable to ragweed. To compare methods, an additional Tauber Trap was deployed alongside the Burkard Trap located 15 meters above street level in midtown Manhattan.

Results/Conclusions

Among the 10 sites, ragweed pollen influx ranged from 51 to 484 grains per cm². In the latter case, both Ambrosia artemisiifolia and Ambrosia trifida were observed growing within 10meters, but there was otherwise no overall correlation between sites where ragweed was observed within 100meters and those where it was not. Whereas proximity of ragweed may still have a bearing on influx, determining this calls for more comprehensive sampling. Other factors may include wind direction, as well as the effects of air turbulence from street traffic and the built environment. There was a broad correlation between the cumulative pollen levels registered by the Burkard Trap at midtown and the pollen influx received by our modified Tauber Trap deployed alongside it. Both traps registered Artemisia as the most abundant followed by Poaceae then by Ambrosia. Both traps received 13 additional pollen types at levels ranging from 5.6% to less than 1%. Among these minor taxa there was less agreement, but both traps received Urticaceae, Chenopodaceae, Asteraceae, Ulmus, Pinus, Plantago, Quercus, Betula and Tilia. The light-pole mounted Tauber Traps register a real and substantial variability of allergenic pollen influx over NYC, a finding with possibly significant public health consequences.