There’s been a subtle, yet unmistakable change in lighting over the past few years. And it isn’t entirely by choice. For nearly two decades, government policies around the globe have been slowly phasing out the classic incandescent light bulb we’ve known since Thomas Edison’s time and pushing a new source of illumination called LEDs.
In just a few years, LED bulbs have become our most prominent source of indoor and outdoor light. You’ll find them in homes, schools, offices, and street lights—virtually anywhere that incandescents once reigned. But the technology’s popularity has little if anything to do with the quality of the light they shine. LEDs beam a much colder light than their comparatively warm incandescent cousins, and they fetch a higher price wherever you buy your bulbs.
The primary driver behind LED’s rise to the top is energy savings. U.S. efficiency standards starting in 2007 helped extinguish many incandescent bulbs from the market, giving a lot of room for LEDs to shine. In most places, a few incandescent options still remain. However, states with stronger standards have more restrictions.
Shining a light in the dark has always been a matter of energy. A couple centuries ago, some form of fire was the only option once the sun went down. Whether it was wood or wicks, something had to be burning to light the dark.
Electric light bulbs changed the game. Incandescent bulbs still radiate heat—they shine by a hot filament found at their core. But compared to fire, incandescent bulbs burn far brighter for much longer. Just imagine how many candles you would need to match a 60-watt bulb.
LED light boasts an even better light-to-energy ratio, producing the same level of lumens (brightness) at a fraction of incandescent wattage. That’s because 90 percent of the energy an incandescent bulb burns goes to heat. LEDs illuminate not by heat (although they do get warm) but rather they work via a special semiconductor that gives off light when an electric current flows through it. LED stands for light emitting diode.
Although LEDs cost more upfront, they promise to cost less over the life of the bulb, because it uses less energy and lasts longer than incandescent.
Still, not everyone is a fan. Despite all the advantages LEDs offer, people can be turned off by the cold quality of light they emit. Although manufacturers have managed to give LEDs a warmer glow as the technology has improved, they still pale in comparison to the familiar, sun-like warmth of incandescent bulbs.
Some researchers are concerned that LED light may also have downsides beyond aesthetics. For example, studies have shown that exposure to LED light may be linked to mental illness, sleep disturbance, hormonal imbalance, and even cancer.
Scientists who explore this area of research say what’s fueling these conditions is the kind of colder light LED bulbs emit—something called blue light. According to a study published in a 2018 edition of the journal Environmental Health Perspectives, exposure to outdoor light at night in the blue light spectrum was associated with breast and prostate cancer.
An Energizing Light
Blue light is nothing new. In fact, it’s been around forever. The sun shines some blue as part of its full spectrum of color illumination. On a clear, sunny day, blue will be the predominant light color thanks to a bright blue sky.
What makes blue light so problematic is the time that we’re exposed to it. Consider that blue is an energizing color. This isn’t a subjective observation, but a scientific fact. Light is composed of particles that travel in waves, and blue light has a short wavelength compared to colors at the warmer end of the spectrum (think red and orange). This means that waves of blue light meet our eyes with greater frequency than the waveforms of other colors.
This energizing feature of blue light is an advantage throughout the morning when the sun is up, your day has just begun, and there’s a lot that you still want to accomplish. However, after the sun sets, and particularly in the last few hours before we go to bed, blue light can influence us in ways that go against the delicate balance of our well-being.
Beyond the Visual
Melatonin is at the heart of why scientists believe blue light exposure at the wrong time of day can lead to health problems. Studies have shown that blue light inhibits the body’s production of melatonin. A disruption in this hormone is known to upset biological processes such as sleep, menstrual cycles, mental health, and immunity. Melatonin is also a powerful antioxidant.
How much melatonin the body produces and when it produces it can impact the entire body. However, when it comes to light’s influence, the process primarily starts in the eyes. The short, rapid wavelength of blue light has been shown to stimulate an ocular pigment called melanopsin, which signals the production or suppression of melatonin.
We often switch on a light or step outside so we can see better, but different kinds of light can influence our bodies in ways we can’t see. For example, our skin can only produce vitamin D when it comes into contact with UV rays, which are plentiful in the sunshine, scant in most incandescent bulbs, and practically nonexistent in LED light.
But even if we’re just talking about the light that meets our eyes, the influence goes deeper than our visual perception.
How this works has only been recently understood. In the past, scientists believed that the human retina only had two types of photoreceptors: rods and cones. Both of these retinal structures helped us understand how we see, but mysteries remained. For example, why did blind patients have a sleep-wake pattern that followed the cycle of a sun they couldn’t see?
In the past few decades, scientists have discovered another structure in the eye, something called intrinsically photosensitive retinal ganglion cells (ipRGCs). These cells are found at the back of our retina, and blue stimulates them. These ipRGCs may be a part of our eyes, but they don’t aid in sight. Instead, they work exclusively to regulate your sleep-wake pattern—also known as the circadian rhythm.
We get most of our blue light exposure from the tablets, phones, and computer monitors we stare at all day and often late into the night. Some of these devices use an LED screen, but most use an LCD (liquid crystal display), which is backlit for illumination.
Whichever screen type you choose, it seems you can’t do without blue. Since blue is a primary color, its light is an essential ingredient in creating the enormous range of colors in photos, videos, and graphics that illuminate your screen. Even a bright white screen requires that indispensable blue light.
A review published in the December 2019 edition of the Journal of Biophotonics explains that chronic exposure to blue light directly before bedtime “may have serious implications on sleep quality, circadian phase and cycle durations.”
“This rises inevitably the need for solutions to improve wellbeing, alertness, and cognitive performance in today’s modern society where exposure to blue light emitting devices is ever increasing,” the review reads.
As people around the world have increased their amount of screen time, awareness of the effects of blue light has grown. Today, some health experts recommend that people, especially those with hormonal imbalances, sleep problems, or vision issues, lay off the screens at least a half hour or so before bed.
If you can’t part with your device, you can buy special orange-tinted glasses designed to block out the blue. Most devices also offer night light settings to minimize blue and mitigate the problems associated with viewing this light too close to bedtime.
And don’t forget to shut off or turn down the LED bulbs that illuminate your evening environment. Consider night lighting with bulbs that have a lower lumen count or try a red bulb. Red has the longest wavelength of all the colors and is therefore least likely to upset your circadian rhythm.
Light at Night
LEDs were first invented in the 1960s, and the first example wasn’t blue, but red. Over the next few decades, engineers from Texas Instruments, General Electric, and Monsanto created other LED colors, but a blue diode didn’t make it onto the scene until the 1990s.
The discovery marked a major turning point for applied LED technology. Blue was deemed necessary to create a light bulb bright enough to match or exceed the once-prevailing incandescent bulb. Government subsidies inspired a bulb with a price low enough for consumers to purchase them. And the price per LED bulb has continued to drop ever since.
As technology marches on, more advancements in lighting are sure to follow. But how will they affect us long term? Lighting isn’t just a convenience. It has become a way of life for generations. It would be hard to cope if we were suddenly forced to revert back to candles and oil lamps.
Electric light has granted humans a level of nighttime activity and illumination that our ancestors could never have fathomed. Whereas the boundaries of the day for people of the past were closely tied to the cycles of the sun, our days now last indefinitely, until we’re finally ready to switch them off.
But like so many other advantages of modernity, artificial light at night (ALAN) comes at a price. Even before the ubiquity of blue light, studies found ALAN to be implicated in the emergence of several diseases, such as metabolic syndrome, obesity, depression, and cancer. In every case, the imbalance of circadian rhythms was to blame.
A 2018 review published in the Journal of Experimental Biology highlights the hormonal influence of ALAN on both humans and animals.
This review doesn’t compare our predominantly incandescent ALAN past to all the blue light we’re now bathed in thanks to smartphone screens and LED bulbs. But researchers suggest that it’s something to consider.
“As governments and agencies begin to switch to LEDs for economic reasons, do we know enough about these alternative light sources to justify policy change?” researchers wrote.