Light Pollution’s Expanding Impact: Allergy Seasons and Human Health
Nighttime light, long recognized as a threat to migrating birds and sea turtles, is increasingly linked to risks for human health, including potentially worsening allergy seasons. Recent research suggests that artificial light at night (ALAN) can extend the period when plants produce pollen, a finding described as “a major public health issue.”
The study, focusing on the northeastern United States from 2012 to 2023 – including urban areas like New York, Boston, and Philadelphia – found a correlation between higher ALAN exposure and increased overall pollen levels, as well as a pollen season roughly one to two weeks longer. Researchers used modeling to control for variables like temperature and precipitation when isolating the effects of nighttime lighting.
While temperature and light are both primary factors influencing when plants flower and produce pollen, artificial light doesn’t replace sunlight. Instead, it “kind of disturbs their circadian rhythm and confuses plants,” explained Lin Meng, of Vanderbilt University and the study’s corresponding author.
The impact of artificial light at night on pollen season extension appears to be comparable in magnitude to that of climate change, according to the research. The two factors act as compounding forces, creating effects greater than either one alone.
Andrew Richardson, an ecologist with Northern Arizona University who was not involved in the study, highlighted the significant economic and quality-of-life consequences of prolonged allergy seasons. “Seasonal allergies cost billions of dollars in healthcare costs as well as making life miserable for those who are highly sensitive,” he said. “If you’re one of those people, then this research is clearly nothing to sneeze at!”
The increasing use of artificial light at night is a relatively modern environmental issue, but one that is rapidly growing. The proliferation of improperly installed lighting contributes to what researchers and policymakers define as “light pollution,” described as excessive or obtrusive artificial light.
A systematic review and meta-analysis published in February 2024 examined the influence of light at night on allergic diseases. The research explored associations between ALAN exposure and the odds of different types of allergic conditions, considering factors like chronotype and shift work.
Beyond allergies, studies indicate that ALAN can have detrimental effects on both humans and wildlife, impacting reproductive and metabolic systems, increasing cancer risk, and affecting mental health. The invention of light-emitting diodes (LEDs) has further complicated the issue, as many contemporary LED lights emit more blue light, which can disrupt biological systems and the human circadian rhythm – the body’s natural internal clock.
