By Katherine Ellen Foley May 17, 2019
These headlines are alarming because, depending on the time of day and your phone or computer’s settings, your eyes are being exposed to blue light right now. LEDs, or light-emitting diodes, are hugely popular—they’re more energy-efficient than traditional lights, and 90% cheaper now than they were a decade ago. All screens have LEDs that emit blue light, as do many offices and homes.
The press release (in French) put out by the Agency for Food, Environment, Occupational Health, and Safety is dire. Authors of the report claim their work “confirms the toxicity of blue light on the retina” while also showing that blue light can seriously disturb sleep-related biological rhythms. Not only that, but it says that there are environmental risks to blue light from LED screens, too.
Oh boy. Danger is everywhere and eminent, it would seem. And yet, if you dig a little deeper, you’ll find you can take a sigh of relief. What the report gets right is that blue light from screens can affect our bodies and the environment. But the risks to typical screen-users eye health is seriously overstated, both by the agency’s own report and press release, and in the news headlines that followed. Let’s break it down.
What is blue light?
Blue light is a component of light present in the normal visible spectrum. It’s on the shorter end of wavelengths we can see, around 400 to 500 nanometers. For context, red light is about 635 to 700 nanometers. Like its name implies, when blue light is reflected off a surface, we see the color blue. White light is a combination of all the different wavelengths of light we can see, and is given off by lamps, screens, and the sun.
There are plenty of wavelengths we can’t see that can be dangerous. Ultra-violet (UV) rays, which the sun also emits, are shorter than the visible spectrum and have enough energy to degrade our DNA. Infrared light is light we can’t see because its wavelengths are too long, but we can feel them in the form of heat. They can also burn us, but they won’t harm our DNA in the same way as shorter wavelengths do.
LED lights, however, do not emit UV or infrared lights. They only emit visible light.
Do LED lights emit blue light?
Yes—but no more blue light (pdf) than other lightbulbs, provided they give off the same balance of shorter and longer light wavelengths. “Warmer” light has more of a yellow tone to it, while “cooler” light, which is similar to daylight, appears a little bluer.
Sunlight is 10 times brighter than typical indoor LED light or screen, which means we get much more blue light exposure from the outdoors.
Do LED lights hurt your eyes?
In the vast majority of cases, no.
The risks to eye health from light exposure come down to brightness. The retina of our eyes have cells called photoreceptors, which pick up light. Too much light can damage these cells.
All LED lighting is rated on its safety on a scale of 0 to 3 used by both the American National Standards Institute and the International Electrotechnical Commission to bring uniformity to LED light labeling. “0” means that the light poses no risk to your eyes, and doesn’t require any kind of warning label. The LED lights present in homes, offices, and your screens, have this kind of a low-risk rating.
The eye-health risks posed by lamps increase as the scale goes up; but notably, those that are high-risk, with a rating of 2 or 3, are usually only present in industrial settings. People who work with these types of lights are required to wear protective gear to filter out some of the blue light. Because blue light has the shortest wavelengths of visible light, there’s some concern that, like UV rays, they could also damage the retina.
Most of us will only ever experience blue light from the LEDs in screens and from ambient lighting—safer settings. Although there are some concerns that LED lighting could lead to vision problems later in life, the science behind these theories is weak. The risks to damaging our eye health from these sources are “negligible” compared to the risks to eye health from smoking, cardiovascular disease, or even regular aging, according to an article from Harvard Medical School.
Does that mean I can look directly into an LED lightbulb?
No! That’s a very bad idea!
When you look into any bright light, like those in headlights of a car or a camera flash, your retinas’ photoreceptors panic. “We call it a ‘blanching of the photoreceptors’,” says Raj Maturi, an ophthalmologist based in Carmel, Indiana, and spokesperson for the American Academy of Ophthalmology. Basically, these cells all fire at once, and need a second to recover afterward.
When exposure to a bright light is brief, it takes our photoreceptors only a second or so to recover before we can see clearly again. In older adults, particularly those with other eye conditions, the recovery period may be a little longer—a few seconds or so, which could create dangerous driving situations.
If you continue to look at a bright light (despite your eyes’ instinct telling you to stop), your photoreceptors will become so overwhelmed they release stress chemicals that can damage nearby tissue. It can take up to a year for this kind of damage to heal.
In addition to damaging your photoreceptors, staring into the sun can also damage the eye with the UV rays it emits. Do. Not. Do. It. No matter how cool you think it may look during an eclipse.
Okay, okay—so if I don’t look directly into an LED light, it’s totally safe?
The French regulatory agency was right in pointing out that blue light from LEDs can mess with our circadian rhythms. Circadian rhythms are our body’s natural hormone cycles that tell us when to be awake and when to be asleep.
When our photoreceptors pick up blue light, they interpret it as daylight, and therefore time to be awake. When they don’t perceive blue light—and blue light specifically—it’s a signal that it’s nighttime, and therefore time to produce melatonin, a hormone that helps us sleep.
Staring at screens late into the evening can trick our bodies into thinking that it’s still daytime, and delay melatonin production. The best way to keep sleep cycles on track is to put any screens on “night shift” mode, Maturi says. This setting filters out blue light (and makes the screen look a little more orange).
(Glasses that claim to filter out blue light rarely eliminate all of it, Maturi says. They won’t hurt you, but they’re probably only useful as a fashion statement.)
The French government report also points out the risks of LEDs to the environment. It’s not wrong: Light pollution is a serious problem. When LEDs light up the sky for our benefit, they mess with local fauna, from birds to turtles, who use light and darkness as signals for when certain activities are meant to take place.
And although this is not a point in the report, it’s worth noting that LED bulbs also contain heavy metals. In the bulb, these pose no threat to us. But when these lights break in a home or office setting, it’s important not to touch them as you clean up, although they can be safely sent to a landfill. If disposed LED lights make it into other settings, like a river, they could harm the animals living there.
But back to my eyes—if my LED screens are safe, why do my eyes hurt when I look at screens for a long time?
Assuming you have otherwise healthy eyeballs, muscle strain.
Eyeballs are restless, curious organs. Their preferred state is looking around to take in all kinds of information about your setting, both near and far. It’s hard for them to focus on one close point for long periods of time, like you may do while reading articles far longer than this one.
The pain you feel after looking at a screen is a simple strain on the muscles around and near the eye, explained Maturi. You can give these muscles a break by looking at something farther away for 20 seconds every 20 minutes or so.