Why Is Everyone Suddenly Talking About ‘Blue Light’? An Explainer


For most people, our days go a little something like this: wake up, check your phone, get ready for the day, check your phone, head to work, stare at your computer, take breaks to go to the bathroom where you check your phone, stare at the computer some more, head home, eat dinner, check your phone, watch television or Netflix, and check your phone before fading off to sleep. That sentence isn’t an exaggeration, it’s understating the case. You know how often you check your phone. You know how much time you spend on screens.

Day after day, hour after hour, most of us stare at screens, and those screens are more than likely blasting us with blue light. All that time exposed to this shorter-wavelength light has both scientists and laymen alike concerned about the consequences. Too much exposure can lead to headaches, eye damage, and more, we’re told. We’re now being warned to limit our exposure to blue light — and there are even products that claim to filter the potentially damaging light.

But is it blue light itself that is actually bad for you, or is this another technological bogeyman conspiracy theory? Why is everyone talking about blue light all of a sudden, and what should you know?

We break it down.

First things first: what is blue light?

If you paid attention in science class, you probably remember that visible light exists within a larger spectrum of light (also known as the spectrum of electromagnetic radiation). All light is radiation, and that electromagnetic spectrum ranges from gamma rays, x-rays, and ultraviolet (on the higher frequency, higher energy, shorter wavelength side) to infrared and radio waves (lower frequency, lower energy, longer wavelength).

Visible light is tucked right in between ultraviolet and infrared light, and just like the electromagnetic spectrum at large, the visible light spectrum ranges from high to low frequency, with blue light being high frequency, short wavelength light and red light being low frequency, long wavelength light.

Historically, our main source of light has come from the sun, which produces more yellow light than any other color, and our exposure to blue light has been quite limited, though humans have always been exposed to blue light in one way or another, and it is necessary for humans to function. Blue light helps regular mood, circadian rhythm (aka your sleep cycle), and boost your attention. There have even been studies that show that blue light therapy can help prevent skin cancer.

So, we’re already exposed to blue light. Why are people talking about it now?

Well, thanks to technological advances, we’re surrounded by more blue light than ever. Why? We can look, in part, to LED (light-emitting diode) technology, which produces quite a bit more blue light than traditional indoor lighting, for the answer:

  • LED lighting is more energy efficient.
  • It uses heat sinks to regulate temperature; cooler than traditional (incandescent or fluorescent) lights.
  • It has a longer lifetime than traditional (incandescent or fluorescent) lighting.

In other words: LED (and its newer, sophisticated cousin, OLED) is a net positive in terms of environmental benefits. But LED lighting is also everywhere now, and it’s the chief driver behind our increased exposure to blue light. You’ll find artificial blue light in the following ways:

  • Phones, laptops, tablets
  • Newer street lights
  • Car headlights
  • Energy efficient lightbulbs (and, hell, even traditional lighting, such as fluorescent bulbs)

Why are people worried about it?

The long and short of it: our exposure to blue light has never been higher. Computer screens, new street lights, smartphones, and more surround us 24/7. Practically speaking, because blue light is higher frequency, that also means it’s higher energy. Blue light’s shorter wavelengths penetrate the eye in a different way than longer wavelength light; blue light, like ultraviolet light, can pass through the cornea and lens and penetrate the retina, the sensitive innermost layer of the eye.

All of these technological advances have happened relatively recently (as in, in the last few decades), and we’ve made short work of surrounding ourselves with a high-energy light at almost all times of the day without really knowing what these levels of exposure will do to the human body.

Is it actually bad for you?

People have long warned that blue light could cause the following:

  • Disruptions to the sleep schedule
  • Headaches and fatigue
  • Digital eyestrain
  • Retinal damage and macular degeneration
  • Certain types of cancer

And research is starting to show that this may very well be true.

As early as 2015, studies from around the world have linked blue light and eye damage, along with sleep disruption. (The same reason that blue light helps increase attention is why late-night exposure can throw your sleep schedule into disarray.) One 2018 study by Chinese researchers explained how the shorter wavelengths of blue light harm our eyes: “Because of blue light’s short wavelength, the focus is not located in the center of the retina but rather in the front of the retina, so that the long exposure time to blue light causes a worsening of visual fatigue and nearsightedness.” Prolonged exposure can cause fatigue and even inflammation of both the cornea and the retina, causing permanent damage to your eyesight.

Most recently, a bombshell report released last week by the French Agency for Food, Environmental and Occupational Health & Safety, a French health authority, warns: blue light is damaging our sleep and our eyes. The agency released a statement along with their findings, in which they warned, “[E]xposure to an intense and powerful [LED] light is ‘photo-toxic’ and can lead to irreversible loss of retinal cells and diminished sharpness of vision.”

And as for concerns about cancer?

According to a study published by Environmental Health Perspectives, a highly regarded publication whose parent agency is the National Institute of Environmental Health Sciences, a study of 2,000 breast or prostate cancer patients and 2,000 controls found:

…those exposed to high levels of outdoor blue light at night had around a 1.5-fold higher risk of developing breast cancer and a twofold higher risk of developing prostate cancer, compared with those who were less exposed. Men exposed to high levels of indoor artificial light also had 2.8-fold higher risk of developing prostate cancer

While this is cause for concern, it’s important to remember that correlation does not equal causation, and this study is the first of its kind to not only look at night-time artificial light exposure, but to separate out the colors. In other words: while the findings are worrisome, this study doesn’t mean that blue light is carcinogenic.

In other words: blue light is absolutely bad for your sleep and your eyesight, but the jury is still out on more serious accusations.

Okay, what should I do if I want to avoid blue light?

There are myriad products out there that claim to filter blue light, including apps for your phone, filters for your laptops and tablets, and even glasses. That said, the science behind these blue light filtering apps is dubious, at best. And as for the blue light filtering glasses? Several studies have shown that those who use blue light glasses, “three hours before bedtime reported better sleep quality and mood than those who didn’t.”

Additionally, consumer tech companies like Dell are aware of these health concerns and working hard on creating screens that have “better color gamuts” and limit blue light exposure. But that’s somewhere in the future.

“With screen time exceeding 10 hours per day, we are taking in amounts of high-energy blue light like never before. Devices are becoming brighter and brighter and new research is identifying concerns around cumulative chronic exposure to devices,” said Justin Barrett, developer of Eyesafe — a new display technology being rolled out by Dell. “Overall, we believe safe-use measures are where the display industry is heading and you will see companies onboarding this type of technology.”

As of now, the best thing you can do to limit your exposure to blue light is to limit your screen time, especially before bed. That means less time in front of your laptops, phones, and televisions — three of the biggest sources of artificial blue light in every day life. Try to seriously limit or stop using screens at least 3-4 hours before bed. And if you must use artificial light at night, try to make sure you choose a warmer light for any light you’ll have on close to bed-time.