Nighttime light is a well-known hazard for migrating birds and sea turtles. New research suggests it may also pose risks for human health.
The study finds that plants exposed to artificial light at night (ALAN) produce pollen for an extended period of time, which is “a major public health issue,” Andrew Richardson, an ecologist with Northern Arizona University, not involved with the study, told Mongabay in an email. “Seasonal allergies cost billions of dollars in healthcare costs as well as making life miserable for those who are highly sensitive. If you’re one of those people, then this research is clearly nothing to sneeze at!”
Two primary factors affect when plants begin flowering and producing pollen: temperature and light. Artificial light can’t replace sunlight for plants, but it does “kind of disturb their circadian rhythm and confuses plants,” Lin Meng, with Vanderbilt University and corresponding author of the study, told Mongabay in a video call.
To isolate the effects of nighttime lighting, researchers used modeling to control for variables including temperature and precipitation. They analyzed pollen count data along with satellite observations of nighttime and daily temperature and precipitation records. The study, from 2012 to 2023, focused on the northeastern United States, which includes urban areas like New York, Boston and Philadelphia.
The researchers found that higher ALAN exposure was associated with higher overall pollen levels in the air and a longer pollen season, roughly a week or two longer. Climate change, and warming temperatures are already known to extend pollen season. Meng said the study found that the impact of artificial light at night is comparable in magnitude to that of climate change. Together, warmer temperatures and nighttime lighting act as compounding factors, producing effects greater than either driver alone.
“This study is an important first step,” Brian Enquist an ecologist with the University of Arizona, not involved with the study, wrote to Mongabay in an email. However, Enquist pointed out that urban plants are often ornamentals, they have more access to water and less competition — all factors that could influence pollen production. “Future work will need to disentangle light effects from urban species composition, water availability, and tree structure more explicitly,” he said. Adding that urban ecosystems impact biological timing in many ways and that “artificial light may well be part of that broader suite of drivers.”
Meng said the public health impact of light pollution is a “blind spot” for urban planners. She plans to share this study with planners and urban stakeholders so they can “take this light pollution impact from pollen into consideration when they build our cities.”
Banner image: Aerial view of New York’s Central Park. Image by Wil540 Art via Wikimedia Commons (CC BY-SA 4.0).
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