Temperature-related changes in airborne allergenic pollen abundance and seasonality across the northern hemisphere: a retrospective data analysis

Abstract

Background Ongoing climate change might, through rising temperatures, alter allergenic pollen biology across the northern hemisphere. We aimed to analyse trends in pollen seasonality and pollen load and to establish whether there are specific climate-related links to any observed changes.Methods For this retrospective data analysis, we did an extensive search for global datasets with 20 years or more of airborne pollen data that consistently recorded pollen season indices (eg, duration and intensity). 17 locations across three continents with long-term (approximately 26 years on average) quantitative records of seasonal concentrations of multiple pollen (aeroallergen) taxa met the selection criteria. These datasets were analysed in the context of recent annual changes in maximum temperature (T max ) and minimum temperature (T min ) associated with anthropogenic climate change. Seasonal regressions (slopes) of variation in pollen load and pollen season duration over time were compared to T max , cumulative degree day T max , T min , cumulative degree day T min , and frost-free days among all 17 locations to ascertain significant correlations.Findings 12 (71%) of the 17 locations showed significant increases in seasonal cumulative pollen or annual pollen load. Similarly, 11 (65%) of the 17 locations showed a significant increase in pollen season duration over time, increasing, on average, 0•9 days per year. Across the northern hemisphere locations analysed, annual cumulative increases in T max over time were significantly associated with percentage increases in seasonal pollen load (r=0•52, p=0•034) as were annual cumulative increases in T min (r=0•61, p=0•010). Similar results were observed for pollen season duration, but only for cumulative degree days (higher than the freezing point [0°C or 32°F]) for T max (r=0•53, p=0•030) and T min (r=0•48, p=0•05). Additionally, temporal increases in frost-free days per year were significantly correlated with increases in both pollen load (r=0•62, p=0•008) and pollen season duration (r=0•68, p=0•003) when averaged for all 17 locations.Interpretation Our findings reveal that the ongoing increase in temperature extremes (T min and T max ) might already be contributing to extended seasonal duration and increased pollen load for multiple aeroallergenic pollen taxa in diverse locations across the northern hemisphere. This study, done across multiple continents, highlights an important link between ongoing global warming and public health-one that could be exacerbated as temperatures continue to increase.

Estimating the Health‐Related Costs of 10 Climate‐Sensitive U.S. Events During 2012

“…Global Change Research Program, 2018). These case studies are consistent with the long-term projections for climate change impacts for extreme heat (Christidis et al, 2011;Hansen et al, 2006;Meehl et al, 2007;Vogel et al, 2019;Zwiers et al, 2011), hurricanes (Keellings & Hernández Ayala, 2019), harmful algal blooms (Hilborn et al, 2014;Poh et al, 2019) and other extreme weather (Nilsen et al, 2011;Papalexiou & Montanari, 2019); allergenic pollen (Anenberg et al, 2017;L. H. Ziska et al, 2019), ozone air pollution (Fann et al, 2015;Kinney, 2018), wildfires (Abatzoglou & Williams, 2016;Liu et al, 2016), West Nile virus (Belova et al, 2017;Paull et al, 2017), and Lyme disease (Monaghan et al, 2015).…”

“…Allergenic pollen levels are affected by climate, because warmer weather, higher humidity, and heightened levels of carbon dioxide in the atmosphere can stimulate the growth of certain plant species and can extend pollen production season (Neumann et al, ; Reid & Gamble, ; Sapkota et al, ; L. Ziska et al, ; L. H. Ziska et al, ). Higher pollen levels from specific trees, grasses, and weeds are associated with asthma exacerbations (Sun et al, ).…”

Climate Change and Childhood Respiratory Health: A Call to Action for Paediatricians

“…Recently, a retrospective analysis of global datasets, with 20 years or more of airborne pollen data in 17 locations in the Northern hemisphere, revealed the significant increase of the pollen load and pollen season duration over time in most analysed locations, in association with the annual cumulative increases in temperature over time. Since air pollen concentrations are supposed to reflect the spatial and temporal changes of plant species, these results suggest that CC, through high temperatures, is already affecting season timing and duration, thereby increasing pollen amounts in the Northern hemisphere [16]. Nonetheless, airborne pollen evolution depends also on pollen production, release and atmospheric dispersion changes.…”

Bioaerosol field measurements: Challenges and perspectives in outdoor studies

“…In addition, the allergen modeling community requires bioaerosol measurements in real time to support model assimilation. At the same time, however, new measurement approaches should be compatible with historical datasets in order to integrate with long-term climatological studies (Ziska et al 2019).…”