LATE SUMMER/FALL GRASS POLLEN SEASON: RETROSPECTIVE ANALYSIS OVER A 6 YEAR PERIOD

Abstract

Introduction Retrospective analysis of cumulative grass pollen data was performed to confirm a grass pollen season in late summer/fall in metropolitan Philadelphia. Methods A review of pollen data collected over 6 years from Burkard air samplers was done at 2 sites. Qualitative and quantitative pollen analysis was performed according to National Allergy Bureau standards. Grass counts were reported in grains per cubic meter per 24 hours (gr/m3/24hr). Results In addition to spring grass pollination, a second grass pollen season was identified yearly at 2 locations, Philadelphia/urban and Mount Laurel, New Jersey/suburban. Combined station data revealed that the second grass season started mid-late August (range August 15th- 28th), peaked September 9th (range August 19th -September 15th) and ended mid September/early October (range September 17th to October 6th). The mean peak grass count was 28.93 gr/m3/24hr in Philadelphia/urban and 30.93 gr/m3/24hr in Mount Laurel/suburban. There was no statistically significant difference in mean peak counts (mean difference 2.0, CI -16.29 to 20.29). Conclusions Our results confirm a second, clinically relevant grass pollen season in both Philadelphia and southern New Jersey. This later season may reflect growth of warm season grasses (big bluestem and indian grass), native to Pennsylvania and southern New Jersey. Pollen levels were sufficient to provoke a significant allergic response in sensitive individuals. Knowledge of this late summer/fall grass season may help identify individuals who may benefit from grass immunotherapy for those with late summer/fall grass pollinosis. Figure. Composite average grass pollen values 2012–2017