Increasing exposure to blue light undermining health of workers
Blue light from digital screens, overhead lighting can cause insomnia
When the City of Ottawa launched a project to replace its old orange streetlights with 58,000 new LED lamps, it quickly heard some criticism. Experts pointed to research showing a connection between LED (light-emitting diode) lights and health problems.
Mixing yellow and blue light creates the intense white of LEDs.
“Unfortunately, the blue affects our circadian rhythm,” Robert Dick, a physics professor at the University of Ottawa, said in an interview with CBC last year.
In the late 1990s, he added, a study found nurses had a 60 per cent higher incidence of breast cancer. After investigating all possible causes, researchers narrowed in on the blue component in light used in the corridors after dark.
“It’s that blue light that prevents your body from recognizing that it is nighttime. At nighttime, you have a lot of restorative hormones that course through your body that fight disease, infection and that reduce stress and anxiety. They even fight incipient cancer cells,” he said. “Those are inhibited when you have blue light shining in your eyes.”
The amount of blue light we are all exposed to has greatly increased in recent years. The screens on digital devices — smartphones, tablets, laptops and televisions — emit large amounts of blue light. There is also now more blue light in overhead lighting.
For many workers, this is a particular problem. Digital devices have become necessary tools in most occupations today. After using them all day, workers go home and continue using them through the evening. The blue light they see at night hinders sleep and can lead to serious insomnia-related problems. Moreover, blue light may cause eye damage over time. But the amount of blue light in the workplace can be reduced, allowing workers to continue using digital devices without the harmful effects.
Visible light is emitted across a spectrum of colours. Blue light is light in the blue region, the high-energy end of the spectrum. Measured in wavelengths, blue wavelengths range from about 400 to 500 nanometres (nm).
“Within that range, the shorter wavelengths — about 400 to 450 nm — are the ones that can cause retina damage,” says Kirsten North, policy specialist with the Ottawa-based Canadian Association of Optometrists and a practising optometrist.
While we have always been exposed to blue light, mostly from the sun, the amount of blue light we see has greatly increased in the last few decades, North says. Lighting technology has improved in energy-efficiency and longevity, but each new type of light produces more light in the blue spectrum. Fluorescent tubes and compact fluorescent lamps emit more blue light than the incandescent bulbs they replaced. Fluorescent lighting is popular in overhead fixtures, especially in warehouses.
The latest technology, LEDs, emits more blue light than fluorescent lights.
LEDs are used in many electronics with screens and are starting to be used more frequently in overhead lighting.
BLUE LIGHT AT NIGHT
Light, in general, inhibits the production of the “sleep hormone” melatonin, and blue light does this to a greater extent than other types of light. During the day, blue light promotes alertness, but at night, exposure to blue light disrupts the circadian rhythm, the body’s 24-hour clock, interfering with a person’s normal sleep habits.
“The eye detects the light and signals to the brain it’s still daytime, and then your brain says, ‘Prepare this person as if they were going out during the day.’ So, all the physiological things that your body does during the day to keep you awake — raising body temperature, increasing cortisol (a stress hormone), lowering melatonin — it will do at night, when it should be doing the opposite,” says Amol Rao, founder of Somnitude in Toronto.
Short-term lack of sleep impairs cognitive function. But if persistent, insomnia can eventually contribute to serious physical and mental health problems, such as breast and prostate cancer, diabetes, obesity, cardiovascular disease and depression.
People working regularly on a night shift are most likely to be affected by blue light.
“We know that blue light alters the sleep cycle. So if you’re exposed to blue light — fluorescent bulbs, LEDs, screens — during your nighttime and then when you leave it’s light outside, you never get that total darkness. There have been studies linking that to all kinds of diseases, including breast cancer,” North says.
Blue light also creates worse nighttime glare than conventional lighting, one of the reasons for concern about LED street lamps. Blue light produces glare in the eyes and so increases safety risks on the road, North says.
“Blue light is harder to focus than other colours. If most of the light coming from LED street lights is blue, then it’s harder to focus. It will slow down your reaction time.”
Over time, blue light may also cause damage to the eye. The short wavelengths penetrate to the back of the eye, harming the retina cells. Long-term, that damage can lead to macular degeneration, a condition in which a person loses his or her central vision (peripheral vision is unaffected) and can no longer see fine details. People looking at computer screens all day are most potentially at risk for eye damage, says Keith Gordon, vice-president of research at the Toronto-based CNIB.
“Typically, there’s not a lot of concern because of the light itself, but people spend hours looking at these screens, so there is a concern that if you spend your day looking at a computer monitor, with that amount of light, you could have long-term damage in the eye,” he says.
It is important to note, however, that the direct connection between long-term exposure to blue light and retinal damage in humans has not been absolutely proven, Gordon stresses.
“I don’t think it has ever been definitively said that long-term exposure to blue light can in fact damage the retina. But there’s an association, and there are animal studies that show that blue light can be toxic to retina cells,” he says.
In addition to retina damage, prolonged exposure to blue light can lead to earlier cataract formation and, most commonly, to eye strain, North says. Hours of looking at a computer screen can produce slightly blurred vision. Many studies have shown that computer eye strain can decrease productivity by 20 per cent, she adds. Eye strain can become a chronic problem if it is not addressed.
Safety mangers can reduce worker exposure to blue light by putting screens that block out some blue light over the computer monitors, North says. Workers should also be allowed to take regular breaks to give their eyes a rest from the blue light. It’s also a good idea, she adds, to have workers see an optometrist regularly, have an eye exam and wear the correct glasses for proper vision.
In addition, it is possible to use software to reduce blue-light exposure, Gordon says. Filter apps, such as the f.lux, which is free, can be installed in computers and mobile devices to adjust light emitted to the time of day: very bright during the day and subdued at night. Moreover, many devices now come with a blue-light reduction mode, a setting the user turns on to reduce the backlight. Like the app, it automatically adjusts light and colour at sunrise and sunset.
“These are two practical things one can do that are fairly easy,” Gordon says.
Workers can adjust the level of blue light emitted from their screens by simply decreasing the brightness of the screen or by altering the contrast by switching to white-on-black.
Safety managers can limit the amount of blue light produced by overhead lighting, Gordon says. Avoid cool white or blue-white fluorescent tubes and instead install ones that are coated, so they produce less blue light and emit a warm white light. Also, replace flickering fluorescent tubes quickly because faulty tubes emit more blue light.
Gordon says it may also be a good idea to stay away from white desks. The effect of the white surface is similar to that created for skiers by a bright sun on snow.
“White desks reflect anything coming out of the computer, so you’re getting a double whammy. If you’re sitting at a white desk and you have a fluorescent light, then it is going to reflect off the desk into your eyes. I would recommend people have dark-coloured desks,” he says.
Glasses that block blue light work by filtering out the shorter wavelengths of visual light that would otherwise activate light receptors in the eye and send a signal to the region of the brain that controls the production of melatonin. These glasses, which have orange-coloured lenses, also come in a “fit-over” size, designed to be worn over prescription glasses.
“What you want to do is cut out the blue light in the two to three hours before you go to bed,” Rao says. “A handful of studies have shown your body actually responds to cutting out blue light in the same way it would if it were nighttime.”
One advantage of the eyewear is that people don’t have to try to give up looking at electronic screens at night, Rao says. The glasses affect colour perception, however, so some kinds of work cannot be done while wearing them.
Workers on night shifts who are concerned about their exposure to blue light should consult their safety manager before getting a pair of glasses that block blue light, Rao says. Blue-blocking glasses reduce alertness so this may not be appropriate at work. Experts are divided, he adds, about whether workers should wear the glasses at night: Some believe night-shift workers need a lot of light to stay alert, while others say disruption to the circadian rhythm should be minimized as much as possible and blue-blocking glasses would help achieve that.
“Shift work is trickier. It requires more careful consideration,” Rao says. “I wouldn’t recommend that (everyone) who works a night shift should wear the glasses. It has to be decided on a case-by-case basis.”
The CSA currently has no standard regarding blue light in its occupational health and safety program. However, there are international standards, Gordon says. One study that tested light-emitting devices found the devices tend to emit levels of blue light well below the safety limits set by the international standards.
“The study looked at all types of light bulbs, computer screens and laptops and they were all in the range of 10 to 20 per cent of the exposure limit of the standard,” he says. “Manufacturers of these devices have to make sure the amount of blue light they emit is significantly less than the standard that is set.”
As the City of Ottawa prepared to roll out its new LED street lamps, Dick told CBC that city managers could reduce some of the adverse affects of the blue light simply by dimming the lights. But it’s a practice most big cities do not follow.
“Life has evolved on Earth for four billion years with the light and dark contrast. It’s literally in our DNA,” he said. “And once you disrupt that light, once you add light in the nighttime — that throws off our biochemistry. There are no winners in that.”
Linda Johnson is a freelance journalist based in Toronto. She can be reached at firstname.lastname@example.org.
5 ways to decrease exposure to blue light