Light Pollution

What is light pollution?

Light pollution is the introduction of artificial light, either directly or indirectly, into the natural environment. Our focus is on light that goes where it should not, such as up into the sky, when it is meant to illuminate the ground.

There are two forms of light pollution:

  • Sky glow (also known as artificial sky glow, light domes, or fugitive light) is the brightening of the night sky from human-caused light scattered in the atmosphere
  • Glare is the direct shining of light.
Skyglow- McDonald Observatory-Bill Wren
Skyglow example at McDonald Observatory. Photo Credit: Bill Wren

How is light pollution harmful?

Human health: Light pollution can affect the production of melatonin in the brain, a hormone which is used for sleeping. Decreased melatonin production has been linked to increased rates of diabetes, obesity, breast and prostate cancer. This can also disrupt human circadian rhythms or “sleep cycle,” and increase exhaustion and irritability. Prolonged exposure to intense light glares can damage human vision and contribute to sight loss, especially for the elderly.

Energy: Light can emit too much or shine up into the atmosphere, causing light pollution, and wasting energy and electricity. Over consumption of energy can have dangerous environmental consequences.

Photo Credit: International Dark-Sky Assocation

Wildlife: Many animals respond to light-based cues. Exposure to artificial light disrupts these cues and their related cycles.


  • Most birds migrate or hunt by moonlight. Light pollution can divert these birds to a city, where they are in more danger of being hit by cars or flying in to buildings.
  • When sea turtles hatch, they instinctively crawl from the beach toward the lighter horizon, which leads them into the ocean. Light pollution can confuse these turtles and lead them further into land, where they will likely die, out of their natural ocean habitat.
  • Many animals, especially predators, are colored to blend in with the darkness, camouflaging them and making it easier to hunt under cover of darkness. Light pollution makes them more visible, and makes hunting more difficult. This can disrupt the natural and essential balance of an ecosystem.
  • Thousands of species, both predator and prey, are nocturnal. Exposure to light pollution disrupts their natural circadian rhythms.

Night Skies: Light pollution decreases night sky visibility, and therefore makes taking necessary measurements for wave and signals technology difficult. This can affect the accuracy of many modern conveniences, including cell phones, GPS technology, television, radios, and other wave-based technology. Light pollution also impedes our ability to enjoy the natural beauty of the night sky.

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Photo Credit: Dan Duriscoe