The impact of weather and climate on pollen concentrations in Denver, Colorado, 2010-2018.

BACKGROUND: Increasing evidence indicates that climate change is affecting the timing of pollen season and concentrations of allergenic pollens. To date, pollen trends and their associations with meteorological variables have not been studied in most of the United States. OBJECTIVE: The purpose of this study was to investigate the effects of weather and climate on pollen concentrations and pollen season timing in Denver, Colorado. METHODS: We retrospectively analyzed tree, grass, and weed pollen counts and meteorological variables from 2010-2018 using linear and Poisson regression models. RESULTS: Pollen season timing did not demonstrate uniform trends from 2010 to 2018. Certain species demonstrated earlier season start dates (linden, oak) or end dates (birch, maple), and others had later end dates (oak, grass). Only a few species demonstrated changes in season duration (linden, oak, maple, birch) and peak date (maple, birch). Pollen concentrations either remained stable or increased over the years. Temperature and carbon dioxide levels increased over the study period, with the exception of decreased temperature in August. Wind speed remained stable or decreased over the study period. CONCLUSION: This study illustrates the complex interactions between pollens and meteorology. Meteorological variables associated with climate change do appear to affect allergenic pollens, though the relationship is variable both amongst pollens and from year to year.