Artificial light at night extends pollen season and elevates allergen exposure
Brandt Geist1, Lin Meng1, Daniel S W Katz2
1Department of Earth and Environmental Sciences, Vanderbilt University, Nashville, TN 37235, USA.
PNAS Nexus
|January 22, 2026
Summary
Artificial light at night (ALAN) significantly extends pollen seasons, leading to increased allergy risks. This study shows ALAN advances pollen season start and delays its end, worsening allergen exposure.
Area of Science:
- Environmental Science
- Ecology
- Public Health
Background:
- Artificial light at night (ALAN) is an emerging environmental stressor in urban areas.
- ALAN disrupts natural light-dark cycles, affecting plant phenology.
- Its impact on pollen season timing and allergy risks is understudied.
Purpose of the Study:
- To investigate the influence of ALAN on airborne pollen season timing and duration.
- To assess the consequences of ALAN-driven allergenic pollen exposure.
- To explore the relationship between ALAN, climate, and pollen season metrics.
Main Methods:
- Utilized daily pollen data from the National Allergy Bureau (2012-2023).
- Incorporated ALAN data from the Visible Infrared Imaging Radiometer Suite.
- Employed gridded Daymet climate data to analyze pollen season start, end, and length.
Main Results:
- Higher ALAN exposure correlated with earlier pollen season start, later end, and longer duration.
- ALAN's effect on season end was more pronounced than on season start.
- ALAN-exposed sites had more days and higher severity of allergenic pollen exposure.
Conclusions:
- ALAN significantly alters pollen season dynamics, extending exposure duration.
- Increased allergenic pollen exposure due to ALAN may exacerbate allergy-related health issues.
- ALAN should be considered in urban planning and public health strategies for managing allergies.
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