Jun 20, 2023 - Science

Light pollution raises human health concerns

Illustration: Annelise Capossela/Axios

Light pollution is increasingly brightening night skies, raising concerns about possible mental and physical health issues caused by disrupted sleep patterns and altered circadian rhythms.

Why it matters: Light pollution at night increased by 7%–10% each year from 2012 to 2022, according to a study published earlier this year, and it will likely continue to climb.

  • The growing glow from artificial light at night is wreaking havoc on astronomy, disrupting animal migration and contributing to climate change.
  • But the stakes are high for human health, too.
  • News reports tend to focus on light pollution's impact on astronomy and stargazing, but the problems are "more immediately relevant to the average person through broader adverse effects," Martin Morgan-Taylor, of De Montfort University, wrote in a study published last week in the journal Science.

What's happening: A growing body of research suggests that nighttime light exposure can impair sleep and disrupt circadian rhythms.

  • "Demographic shifts toward increasingly urban living mean that most humans are exposed to higher levels of light at night," according to another study in the special issue of Science that highlighted the ways light pollution is changing the environment, astronomy and the human body.
  • Studies focusing on night workers have shown exposure to light at night can disrupt circadian rhythms and increase the risk of cancer, heart disease, hypertension, depression, Type 2 diabetes and other health issues.

The intrigue: It's also possible that light pollution's effect on circadian rhythms and sleep could increase the risk of bipolar disorder and other mental health conditions.

  • "Over the last several years, we've learned a lot about bipolar disorder particularly, but also general mood disorder and how light is one of the biggest risk factors," Kathleen Merikangas, a researcher at the National Institute of Mental Health, tells Axios. "Their reaction to light, and their circadian rhythms look like that's the core disturbance in this disorder."
  • A study published in 2020 in JAMA Psychiatry suggests more light pollution could be associated with a higher prevalence of anxiety and mood disorders in adolescents.

Yes, but: Scientists focusing on these issues stress there isn't enough research to determine exactly how light pollution could be harming people today.

  • "We need an aggregate view of environmental exposures if we're going to try to think about these issues and human health. Our field of human health mainly looks from the level of the individual," Merikangas said.
  • Research on the health impacts of light pollution is also complicated because some individuals are more sensitive to light, affecting their sleep patterns and circadian rhythms differently.
  • It's also difficult to connect overall light pollution outdoors to an individual's experience of that light indoors. Curtains, for example, could block out much of the light at night.

What to watch: Some experts are now calling for more stringent government regulations to rein in light pollution.

  • "Education can describe how addressing light pollution is a readily achievable balance between the competing interests of the need to light against the adverse consequences, not simply a call to turn off all the lights to look at the night sky," Morgan-Taylor writes.
  • Researchers also stress the need for a full accounting of the economic costs of light pollution, possibly revealing how wasteful high levels of artificial light at night could be financially.
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