Long-term pollen trends and associations between pollen phenology and seasonal climate in Atlanta, Georgia (1992-2018)

Background: Previous research has revealed that airborne pollen concentrations and phenology in allergenic plants are changing. In addition, variations in seasonal climate are known to affect pollen phenology in trees, weeds, and grasses. Objective: To investigate localized trends in pollen concentrations and pollen phenology over time and the effect of seasonal climate variations. Methods: We used daily pollen count concentrations from a National Allergy Bureau pollen counting station located in metropolitan Atlanta, Georgia, for 13 allergenic taxa. To evaluate long-term trends over time, we developed linear regression models for 6 pollen measures. To evaluate the effect of seasonal climate on phenology, we developed regression models using seasonal climate measures as independent variables and pollen measures as dependent variables. Results: For several tree pollen taxa, pollen concentrations increased over time, including oak and juniper pollen. In multiple species, pollen seasons trended toward an earlier release throughout the 27-year period. Variations in seasonal climate did have an effect on pollen counts and the timing of pollen release but varied by taxa. Generally, warmer spring temperatures were associated with an earlier pollen release. In addition, increased precipitation from the preceding fall was associated with increased pollen concentration in the spring months. Conclusion: Allergenic pollen concentrations for several types of pollen are increasing and trending toward an earlier pollen release in Atlanta, Georgia. Warmer temperatures preceding the pollen season were associated with the earlier pollen release.