Pollen Effects on Asthma, Allergic Rhinitis and Finger Wound Emergency Department Visits, Between 2000-2010, in Baltimore, Maryland

BACKGROUND: Asthma and allergic rhinitis are influenced by pollen and criteria air pollutants. Higher temperatures result in increased pollen and more ozone.  It is possible that pollen effects on respiratory emergency department (ED) visits decrease as the distance between the pollen counting station and where persons live increases.  This study used 11 years of pollen and ED data to evaluate the contribution of pollen levels and type on ED asthma and allergic rhinitis visits relative to a control disease, finger wounds, after controlling for PM_2.5 and O₃.   

METHODS: Data sources included daily pollen readings from the National Allergy Bureau (NAB) certified pollen counting station in Baltimore, and PM_2.5 and O₃ readings from the closest on-the-ground ambient air monitor.  Daily temperature readings were obtained from the Baltimore-Washington International (BWI) airport.  Asthma, allergic rhinitis and finger wound ED visits were obtained from the Maryland Health Services Cost Review Commission (HSCRC).  The electronic data files were aggregated to residential counties and successive months and then linked.  All statistical analyses were carried out using PC SAS version 9.3.  Alpha was set at p<0.05.

RESULTS: Significant Odds Ratios (ORs) confirmed that weed and ragweed contributed more than tree or grass pollen to asthma ED visits, while the opposite pollen type influence occurred for allergic rhinitis.  Relative to 2000, ORs from 2001 to 2010 were significantly larger for allergic rhinitis than for asthma, and protective for finger wounds.  ORs were also significantly larger for asthma and allergic rhinitis at a distance of 0-10 miles than at a distance of 11-20 miles.  Correlation analyses between pollen sources and temperature produced higher R² values in adjusted than in unadjusted analyses.  There were significant increases in temperature, pollen, asthma and allergic rhinitis visits in 2009-2010 relative to 2000-2001.      

CONCLUSIONS: By using 11 consecutive years of ED visits it was shown that pollen does contribute to asthma and allergic rhinitis visits in a way that was different from the pollen effects on finger wounds.  But, there was an inverse relationship between pollen monitor location and residence location of patients who were seen in the ED for asthma or allergic rhinitis.  Because temperature, pollen and respiratory ED visits were higher at the end than at the beginning of the decade, these results suggest that it may be possible to use an 11 year temporal window as a proxy for outcomes that have been previously attributed to climate change.