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Bright street lighting (symbolic image).
© YAY Images/Imago
LED lights are increasingly replacing conventional light bulbs.
That's a problem: they make the sky bright and can affect health.
At night, bright stars often cover the dark sky.
At least they used to.
As society developed, the stars on the horizon became less and less visible.
In a county in Washington state, the clarity of the night sky was marred by lights shining upward and obscuring the view.
This light pollution would only get worse.
An unexpected increase in pollution occurred after Chelan County switched to LED lights, which glow brightly and use less energy than traditional light bulbs.
A year after the change began, the additional glare obscured about half of the previously visible stars.
What happened there is not an isolated incident.
In recent years, cities and communities around the world have taken part in a radical revolution - the revolution of our light bulbs.
Traditional orange high pressure sodium lamps are being replaced with more energy efficient, whiter and brighter LED lamps (light emitting diodes).
But the advance of LEDs also poses new problems for our night sky and our health.
Scientists have found that the night sky has become nearly 10 percent brighter every year for the past decade because artificial lights, especially LEDs, emit too much glare.
Street lights are part of the problem, as are sources such as illuminated billboards and stadium lighting.
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Outdoor lights have a negative impact on health
The same outdoor lights also affect our health.
Common types of LED lights contain higher levels of blue wavelengths, which can affect people's nightlife.
They disrupt our circadian rhythms, reduce the effectiveness of our immune system and increase the incidence of certain diseases, including cancer.
“People need to understand that LED lights are being installed everywhere, not just in streetlights, but in all directions,” said Jim White, senior energy efficiency engineer for the Chelan County Public Utility District, who helped the district convert to LED lights helped.
But he added: "It's a form of pollution that we could solve."
Authorities and organizations such as the National Park Service and the American Medical Association have made recommendations on how to reduce light pollution and its harmful effects on life.
The changes start with what type of LED light you should buy in the first place.
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Bring light into the darkness of the problem
The problem has come to light in recent years with the advent of new LED technology.
LED lamps are the Olympic marathon runners among light bulbs: They use up to 90 percent less energy and last up to 25 times longer than conventional light bulbs.
Since it is the most energy efficient light bulb on the market, it is not surprising that so many people choose this technology.
The Department of Energy estimates that LEDs accounted for about 19 percent of all lighting installations in 2017 and saved about 1 percent of total energy consumption in the United States.
By 2035, 84 percent of lighting systems should be converted to LEDs.
Street, park, building exterior and area lighting - applications that typically have a high lumen value (a measure of brightness) - are expected to be almost entirely converted to LED lights by 2035.
White was excited to see Chelan County, which is in the middle of the state and has a population of about 80,000, joining the LED lighting revolution.
Beginning in 2014, the Chelan County Public Utility District began meeting with local governments, municipalities and agencies to discuss what would be needed to replace streetlights.
In 2018, a $1.9 million project, funded in part by a federal grant from the Washington State Department of Commerce, began to install nearly 3,700 high-pressure sodium street lamps (approximately 60 percent of street and area lighting). to be replaced by LEDs.
LED lights make the sky brighter - stars disappear
The energy savings were clearly noticeable.
After the switch, the new lights saved 2,612,491 kilowatt hours - enough to power about 120 all-electric homes in the district for a year.
But there were downsides: National Park Service researchers found that the LED lights washed out more stars, especially near the horizon.
"You can see that the illumination is getting bigger, so it reaches higher in the sky... the entire sky got brighter," said Li-Wei Hung, an astronomer with the National Park Service who is leading a study on the LED switch published in Chelan County.
“Just a few years ago, this was a really new insight for us.
Does switching to LEDs really reduce light pollution or increase it?
We [didn’t] know for sure.”
Camera data showed that the sky over local Burch Mountain was 60 percent brighter after the county completed the switch in 2019 than in 2018. The new artificial light was 3.69 times that of natural light after the switch;
Before the change, the artificial lights produced 2.30 times the natural light.
White said the increased pollution was "a total surprise" because the Public Utility District tried pointing the lights at the ground, but the light was still scattering.
Detailed data on individual cities' nighttime glow is difficult to come by, making the Chelan County switch an important case study in understanding both the good and bad effects of LED lights.
However, observations and anecdotes show that Chelan County is not alone.
From 2011 to 2022, reports from citizen scientists have found that the average night sky has become 9.6 percent brighter each year, which researchers attribute to the replacement of LED bulbs.
Some cities, such as
Some cities, such as Washington DC, have paused switching to LED lights after residents complained about the bright lights disrupting their sleep.
But why does the light from LED lamps appear more noticeable in the night sky than that of other types of lighting?
The answer lies in the blue light of the LED.
The problems with blue light
LED bulbs emit more blue light than regular light bulbs.
Blue light has a shorter wavelength (450 to 495 nanometers) and a higher frequency, causing air particles to vibrate faster and be scattered more widely in the atmosphere than other colors.
The blue light is redirected in different directions in the sky.
This is also the reason why our sky appears blue.
The human eye is also very sensitive to the wavelength of blue light.
You may remember two types of photoreceptors in our eyes, the rods and cones, which help us see colors and shades.
In recent decades, scientists have identified the function of another photoreceptor, the intrinsic light-sensitive retinal ganglion cell (ipRGC).
These photoreceptors are sensitive to shorter wavelengths and help keep people awake by suppressing a hormone called melatonin, which plays a role in our sleep.
“One of the hallmarks of our circadian clock is this timing of melatonin production.
Melatonin is associated with sleepiness,” says Manuel Spitschan, a neuroscientist at the Technical University of Munich and the Max Planck Institute for Biological Cybernetics.
“Exposing people to light at night or in the evening suppresses the production of melatonin.”
Spitschan explains that when blue light hits our eyes, the ipRGCs begin firing rapidly due to a light-sensitive molecule called melanopsin, which converts photons into an electrical signal to the brain to suppress melatonin production.
The more photons the ipRGC captures, the stronger the signal produced by the photoreceptor, resulting in suppression of melatonin production.
Without melatonin, which triggers sleepiness, people are more likely to stay awake longer.
Disturbances in our circadian rhythm have been linked to cancers such as:
B. Breast cancer, and classified by the World Health Organization as probably carcinogenic.
Other research has shown that disruptions to our circadian rhythm are linked to some heart problems.
“We react more sensitively to blue light at night than during the day,” says Chris Kyba, who quantifies artificial light in the nighttime environment at the GFZ German Research Center for Geosciences.
Solutions to limit light pollution in your environment
There is a world where there are more energy efficient LED lights that do not significantly impact nighttime landscapes or our health.
Light pollution "can be improved with LEDs, but you have to be very careful about the design," said Ashley Pipkin of the National Park Service, a biologist and co-author of the Chelan County light pollution study.
These solutions - from purchasing a specific type of LED light to making changes that reduce glare - can be implemented both on a city level and for individual homes.
Choosing the right light and brightness for your needs
The National Park Service says one way to reduce light pollution of the night sky is to consciously consider where to place the lighting: Is a light really necessary in that location?
And what brightness is appropriate for this light use?
Pipkin explained that when it comes to incandescent bulbs, we typically think of wattage, meaning how much energy the bulb uses, but with LEDs, our focus has to change.
LEDs use fewer watts than traditional light bulbs, and you should choose a bulb based on the number of lumens, often referred to as brightness.
Many people use much brighter LED bulbs than necessary, especially outdoors.
Ideally, you can purchase an LED bulb with a much lower wattage and still have the same brightness as an incandescent bulb.
A 30-watt LED light bulb has the same number of lumens as a 250-watt light bulb, according to the National Park Service.
However, Pipkin added that “the industry often does not provide enough low lumen options.”
Additionally, it may be unnecessary to replace every traditional light bulb with an LED bulb.
“You don’t need that many watts to light a street corner,” White said.
Use warmer LED lamps
Not all LED bulbs are the same.
When you go to the store, you may see some LED bulbs listed as 4,000 Kelvin, 3,000 Kelvin, or even 2,000 Kelvin.
These temperatures correspond to the appearance of light, which is either warm (more yellow) or cool (bluer).
Since our eyes are sensitive to blue light at night, doctors recommend purchasing LED bulbs with warmer colors, such as yellow or amber.
This means using LED bulbs with less than 4,000 Kelvin.
On average, LED lamps with 4,000 Kelvin have a blue content of around 29 percent.
At 3,000 Kelvin it is around 21 percent.
Nowadays there are LED lamps with only 2,000 Kelvin.
Warmer colors also scatter less in the atmosphere than the cool blue light.
But light manufacturers have been slow to switch to warmer hues, said Mario Motta, a retired cardiologist who co-wrote the AMA's recommendations for reducing light pollution.
When he wrote the recommendations more than five years ago, he recalled facing pushback from companies that had already purchased a surplus of the highest blue light bulbs.
White, of Chelan County, said there isn't enough demand yet for manufacturers to produce many lamps as low as 2,000 Kelvin.
“We need more people to ask and insist on it,” he said.
Block or limit light
In your home, blackout curtains can prevent streetlights from entering bedrooms, which can limit the impact on your sleep.
Motion detectors, timers, and dimmers can also help reduce the number of hours of unnecessary light while saving more energy.
Direct light rays downwards
Experts recommend pointing the light downwards outside the home or in public spaces.
Avoid uncovered or exposed lights that emit light upwards and horizontally.
The angle and height of the light can also affect the spread of the light beam.
Directing LED light beams downward can reduce, but not necessarily eliminate, light pollution - as was seen in Chelan County.
Bright light with a high blue content, Pipkin said, can bounce off the ground and be scattered into the night sky, further contributing to light pollution.
That's why it's important to purchase LEDs with warmer temperatures and lower lumen values.
Since switching Chelan County's street lighting to LEDs, White and his colleagues have not made any other changes.
They plan to make changes as more advanced commercial products become available, allowing, for example, lighting to be dimmed or brightened after a certain time at night as vehicles approach.
With better changes in the future, White hopes the stars will once again fill the sky at night.
“I love getting out my telescope and seeing the rings of Saturn, the stars and the moons of the other planets.
We tried everything we could to do this with the best technology available,” said White.
“It’s a common problem that everyone should be aware of.”
To the authors
Kasha Patel
writes the weekly Hidden Planet column, covering scientific topics surrounding Earth, from our inner core to space storms headed toward our planet.
She also reports on weather, climate and environmental issues.
Emily Sabens
is a digital designer who creates content for The Washington Post select app and By The Way.
Kati Perry
has been working on the Washington Post's graphics team since 2022 and focuses on politics.
Daniel Wolfe
is a graphics reporter at The Washington Post covering the West Coast.
We are currently testing machine translations. This article was automatically translated from English into German.
This article was first published in English on June 23, 2023 at the “Washingtonpost.com” - as part of a cooperation, it is now also available in translation to readers of the IPPEN.MEDIA portals.