The Health Aspect of Light
– Light from a Biochemical Approach.
By Garry Hannah
Until the advent of artificial lighting, the sun was the major source of lighting, and people spent their evenings in (relative) darkness. Now, in much of the world, evenings are illuminated, and we take our easy access to all those lumens pretty much for granted.
But we may be paying a price for basking in all that light. At night, light throws the body’s biological clock—the circadian rhythm—out of whack by supressing the body’s natural night time release of melatonin, an antioxidant compound that has been shown to protect biological molecules such as DNA. With this, sleep suffers. Worse still, melatonin suppression has far worse consequences than simply poor sleep outcomes: it has also been shown to increase the risk of cancer, impair immune system function, and possibly lead to cardiometabolic consequences such as type 2 diabetes, metabolic syndrome, obesity, and heart disease.
Recent studies have shown that shifts in the body clock can have devastating health effects because it controls not only our wakefulness but also individual clocks that dictate function in the body’s organs. In other words, stressors that affect our circadian clocks, such as blue-light exposure, can have much more serious consequences than originally thought.
While organizations such as the International Dark-Sky Association urge caution on using white LEDs for outdoor night time lighting, some scientists are already calling for regulations to totally ban the outdoor use of blue-rich light.
Where do LEDs come in?
You come into contact every day with light-emitting diodes (LEDs) — they illuminate alarm clocks, new televisions, traffic lights, and smartphone displays. Increasingly, you will see white-light versions of LEDs becoming available for energy-efficient home lighting, car headlights, streetlamps, and other urban lighting. You see, every LED light ever made produces light in a royal blue colour when switched on. Yes, ordinary incandescent lights also produce some blue light, however this is less than most fluorescent light bulbs and far less than LEDs. In order to change a blue LED to white, yellow, red, green, etc it is covered with a layer of phosphor. The thickness and tint of the phosphor creates the desired visible colour and reduces the blue-rich colour released into the atmosphere. Modulating the amount of blue rich light we produce helps people to relax or be alert, go to sleep or stay awake. It also enhances the aesthetic environment.
So blue-rich lights—which are beneficial during daylight hours because they boost attention, reaction times, and mood—are also the most disruptive at night. And the proliferation of electronics with screens, as well as 3000k and above LED lighting, is increasing our exposure to blue wavelengths, especially after sundown.
Although we are not 100% clear on all the effects on night time lighting, we do now know for certain that exposure to blue-rich light suppresses the secretion of melatonin, a hormone that influences circadian rhythms, and there’s more evidence being released every day that lower melatonin levels have a strong association with cancer.
While light of any kind can suppress the secretion of melatonin, blue light does so more powerfully. Harvard researchers and their colleagues conducted an experiment comparing the effects of 6.5 hours of exposure to blue light to exposure to green light of comparable brightness. The blue light suppressed melatonin for about twice as long as the green light and shifted circadian rhythms by twice as much (3 hours vs. 1.5 hours). This shows not only the long term concerns of reduced melatonin, but also the immediate short term influence on circadian rhythm and the body clock.
With serious consequences like these, preventing melatonin suppression should be a top priority in anyone’s healthy lifestyle.
Recent studies have shown that shifts in this clock can have devastating health effects because it controls not only our wakefulness but also individual clocks that dictate function in the body’s organs. In other words, stressors that affect our circadian clocks, such as blue-light exposure, can have much more serious consequences than originally thought.
Thomas Jefferson University neuroscientist George Brainard, was among the first researchers to investigate how different wavelengths of light affect the release of melatonin, and Harvard University neuroscientist Anne-Marie Chang, recently discovered that the effects of light-emitting devices on circadian systems extend way beyond evening and into the following morning.
This can lead to drowsiness, lack of concentration and inability to function safely. A long day, followed by a few hours of blue-rich light in the evening can have an adverse effect the following day. The negative effects of sleep deprivation are serious: short, interrupted, and/or unsettled sleep is associated with cardiovascular disease and diabetes risk factors, depression, automobile and workplace accidents, learning and memory problems, and an overall increase in mortality.
In another study of blue-rich light, researchers at the University of Toronto compared the melatonin levels of people exposed to cool (above 3000k) indoor light who were wearing blue-light–blocking goggles to people exposed to below 3000k light without wearing goggles. The fact that the levels of the hormone were about the same in the two groups strengthens the hypothesis that blue light is a potent suppressor of melatonin. It also suggests that shift workers, especially in a hospital environment, or similar, where 4000k lighting and above is typical are very exposed, and could perhaps protect themselves if they wore eyewear that blocks blue light, or if an alternative in lighting can be offered. Hospitals, and similar environments, need to take this into account when looking at lighting selection.
The ultimate design in that environment is colour temperature changing systems of light that are also dimmable and positioned only where it is actually needed. This allows 4000k lighting when required, but can be reverted back to 3000k or below, when only ambient lighting is required.
In an outdoor area, light facing up is never for the benefit of people, it is a waste of both intended purpose of illumination, as well as power, all while having a damaging effect on the environment. Light facing down, shielded correctly and brought down to a height where it is most beneficial, will reduce skyglow (environment impact), power consumption (financial impact), glare (safety) and aid trafficability with smoother facilitation.
What you can do
Use dim red or green lights for night lights. Red light has the least power to shift circadian rhythm and suppress melatonin.
Avoid looking at bright screens beginning two to three hours before bed.
If you work a night shift or use a lot of electronic devices at night, consider wearing blue-blocking glasses. Other options may include adaptive controls like dimmers, timers, and motion sensors.
Always choose fully shielded fixtures that emit no light upward
Use “warm-white” or filtered LEDs (CCT < 3,000 K; S/P ratio < 1.2) to minimize blue emission
Consider dimming or turning off the lights during overnight hours
Avoid the temptation to overlight because of the increased luminous efficiency of LEDs
Only light the exact space and in the amount required for particular tasks
Expose yourself to lots of bright light during the day, which will boost your ability to sleep at night, as well as your mood and alertness during daylight.
Until the 21st century, scientists only knew of two types of light-sensitive cells in the eye: rods and cones. But in 2001, David Berson from Brown University established that the eyes of mammals contain a third type of cell for absorbing light.
A 2005 study by chronobiologists in Basel, Switzerland showed that human volunteers exposed for two hours to 460 nm light at night experienced greater reductions in melatonin, a hormone regulated by the body’s circadian system, than when they were exposed to a roughly yellow-green light with a higher-wavelength of 550 nm. Melatonin, in addition to helping the body maintain a regular 24-hour rhythm of wakefulness and sleep, is an antioxidant compound that has been shown to protect biological molecules such as DNA.
In the Oct. 2011 issue of the Journal of Environmental Management, Haim of the University of Haifa and his co-authors calculate that white LED light can reduce melatonin levels five times more than the older low-pressure sodium lamps, which produced yellow-orange coloured lights often seen in parking lots. Haim and his co-authors call for a “total ban of the outdoor emission of light at wavelengths shorter than 540 nm to reduce the effects of decreased melatonin production and circadian rhythm disruption in humans and animals.” This is achievable with LED provided the colour temp is 3000k or below. They also call for increased consumer awareness and for bulb producers to state the wavelengths of light produced by their bulbs.