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Outdoor Lighting and Light Pollution: What You Need to Know

Many of us take the luxury of lighting for granted. We casually flip on switches to sit outside at night and enjoy a bowl of ice cream. We set our smart home automation systems to turn our lights on at night automatically, and more often than not, those lights are on for longer than we're actively using them.

Your outdoor lighting may include your neighborhood streetlights, decorative lamps lining your front entryway, festive string lighting, safety lights, and even light emanating from inside your home. Outdoor lighting makes us feel safer when night falls, improves visibility, and makes it possible to enjoy evening entertainment, including swimming and grilling. But almost every luxury comes at a price. What is the cost of our enjoyment of outdoor lighting for our health and our environment?

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By Laura Bourland, Rise Writer

Apr 13, 2025 · 6 min read

What is Light Pollution?

The International Dark-Sky Association (IDA), based in Arizona, defines light pollution as "the inappropriate or excessive use of artificial light." Artificial light "refers to any light source that is produced by electrical means."

Light pollution has four distinct categories:

What Is Glare Light Pollution?

Light pollution glare refers to excessive brightness. You may associate glare with squinting, and other visual discomfort felt when in the presence of artificial light, such as bright street lamps.

What Is Skyglow Light Pollution?

Skyglow light pollution is easily seen from satellites, airplanes, and even the International Space Station. Skyglow is the brighter night sky seen over areas where people live (and use lights at night).

What Is Light Trespass?

Light trespass refers to stray light that falls outside of its intended area. You can witness this yourself by moving out from under a streetlamp and walking away until it becomes hard to see again.

What Is Clutter Light Pollution?

Clutter type light pollution is prevalent in urban areas where multiple lights may overlap, creating an overly bright and confusing light environment.

While light pollution may not seem like a big deal, it is, in fact, a huge deal for our health. National Geographic published an article about how light pollution contributes to chronic environmental and health problems for every affected person, animal, and plant.

Facts About Light Pollution

Simply knowing the facts about light pollution can go a long way toward making the necessary changes in your lifestyle to contribute to decreasing the effects of light pollution. The problem is, most people don't know how significant our luxurious lighting addiction is!

If you live in a populated area (most people do), you can probably go outside at night and still see in front of you, but can you see the stars above? The Suomi NPP satellite has studied light pollution at length. It has concluded that one-third of all humans worldwide cannot see the Milky Way. Similarly, the World Atlas of Artificial Night Sky Brightness conducted a study in 2016 that found that a whopping 80% of the entire population on Earth lives with skyglow.

For most of our human history, we've lived without light pollution - relying on fire, candles, and fuel-powered lamps. Philosophers, astronomers, physicians, and farmers embraced the darkness. They used the night sky to learn, track weather patterns, and count time by the moon's phases and the position of the stars and planets. But as the population grew and artificial light became more accessible, light pollution has increased astronomically. A 2017 study found that overall light pollution increased by about 2% just between 2012 and 2016.

Light trespass can be observed as much as 40 miles outside a brightly lit city center, like Las Vegas. Whole cities with dense human populations like Singapore and San Marino are visible with the naked eye from outer space.

What are the Main Causes of Light Pollution?

Every artificial light contributes to light pollution, but some have a more significant impact than others.

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When you go out tonight, pay attention to the lighting around you. You'll notice your car's headlights, streetlamps, lighted signs for the various businesses in your neighborhood, porch lights, patio lights, and maybe even spotlights and searchlights. If you live in an urban area, you may also witness light pollution clutter as one light crosses and blends with another, creating an unnecessarily bright space.

LED lighting is growing in popularity for its energy efficiency. Still, while it has decreased overall energy consumption, LEDs haven't moved the dial on light pollution. Because they are more environmentally friendly, many people and businesses tend to overuse LED lighting. While LED lights may appear white, they do contain wavelengths of blue light. Scientists are actively studying blue lights for their impact on human health. The IDA recommends installing safer, cooler outdoor light bulbs of no more than 3000 Kelvins.

How Does Light Pollution Affect Our Planet and Us?

Amanda Gormley, of the IDA, ties the night sky's disappearance to our ever more fast-paced world. She says that something essential, even a part of ourselves, is lost when access to the night sky is lost.

We lose that sense of stillness and awe that should be right over our heads every night.

The Effect on Humans

While extending our days and evenings outdoors may make our lives more productive and fun, human beings desperately need darkness to function at our best.

Numerous studies have been conducted on employees who work night shifts, including truck drivers, flight attendants, overnight construction crews, and police officers and dispatchers. A 2007 study by the World Health Organization "declared shift work a risk factor for cancer." A 2012 study by the American Medical Association warns that lighting the night can create potentially harmful health effects and hazardous situations.

Humans rely on ingrained biochemical rhythms, run by the natural environmental change from morning to night each day. While we can sleep during daylight hours, shift workers can vouch that sleeping at night is much easier and more refreshing. Natural sunlight photons hit the retina of the eye, regulating the pineal gland in the brain responsible for the production of melatonin. In a natural environment, where we wake with the sun, melatonin helps regulate sleep, body temperature, appetite, and metabolism.

Unfortunately, artificial light used when it's naturally dark outside, "interferes with the circadian rhythm by stunting the normal ebb and flow of melatonin." This unnatural disruption has been linked to obesity, heart disease, diabetes, depression, and cancer.

The Effect on Animals

Like humans, animals are also reliant on circadian rhythms that regulate their sleep, hunting, migration, and breeding. Unfortunately, animals are subjected to human light pollution through skyglow and light trespass that stretches much further than the area we intend to light.

For example, baby sea turtles use the moon to navigate underwater while they grow and learn. But in Florida, where large populations of sea turtles live just off the coast, light pollution creates "false moons." These false moons cause baby turtles to wander out of their natural environment and into populated neighborhoods and roads. David Godfrey of the Sea Turtle Conservancy explains, "There are tens of thousands of hatchling disorientations every year. Light pollution is one of the two highest sources of mortality for hatching sea turtles along our [Gainesville, Florida] coastlines."

Among the many animals impacted by light pollution, birds can easily be studied around the world. In Toronto, Canada, birds are often lured by artificial lighting, causing them to crash into buildings, falling to their death on the pavement far below. Unfortunately, most people aren't aware of this occurrence as larger, predatory animals often devour the deceased birds before humans hit the streets for their morning commute.

What Can You Do to Reduce Light Pollution at Home?

While light pollution is devastating, it's one form of pollution on which we can take immediate action to reverse its effects and truly make a difference! Christopher Kyba, from the German Research Center for Biosciences, explains that undoing the effects of light pollution can reduce energy use with virtually no loss to anyone. Here are some easy, low to no-cost actions you can take today:

Only turn on lights when you need them. Turn them off when not in use. This will save you money on your electric bill as well.
Switch out bright bulbs with warmer light bulbs.
Install dimmers, timers, and motion sensors.
Only use light fixtures that shield light from the top and sides. (The LEED rating system for commercial buildings provides points for outdoor lights shine directly downward and are shielded from the top and sides.)
Opt for lights that are closer to the ground.
Keep your blinds and curtains closed at night to prevent indoor light from needlessly shining outdoors.
Spend the hour before bed away from the blue light of the TV, your phone, computer, and tablet.
Avoid turning on the lights if you get up at night.
Buy Dark Sky Approved light bulbs and fixtures.

Perhaps more importantly, we can make light pollution a part of your everyday conversations with friends, family, neighbors, and coworkers. Many people simply don't know about the harmful impact of light pollution. The more people are aware, the more significant the impact we can have at reducing and reversing its effect.

Rise Writer

Expert. Practical. Sustainable.

Article by

Laura Bourland

Laura grew up in the California suburbs, far removed from environmentalism, but nature always has a way. She uprooted her life in 2015, moving to the countryside of Washington to live a more sustainable and simple life on 12 acres. She and her fiancee are learning on the job as they attempt everything from gardening and natural pest control to eco-friendly building and home improvement.

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