An international team of opthalmologists, neurologists and biologists warn that the blue light in LED bulbs and screens presents an untold risk to human health… LEDs are far more disruptive to circadian rhythms than incandescent, halogen, and even fluorescent lights, study finds
The invention of the incandescent light bulb in the late 19th century, followed by halogen and fluorescent lamps in the 20th century, changed the human lifestyle, the authors of a recent study write. Easy access to light, even at nighttime, made us more productive, educated and industrious.
But the invention was not without its downsides, the scientists say. Exposure to light at night disrupts our circadian rhythms, potentially leading to a host of health problems, ranging from “depression to diabetes, hypertension, obesity, and cancer.”
The problem has been exacerbated since the nobel prize winning invention of the blue light-emitting diode (LED) of the 21st century, the authors of the report say, as blue light is the highest intensity light on the color spectrum and therefore, the most disruptive to our circadian rhythms.
Almost all LED lamps currently on the market use a combination of a blue LED with a yellow fluorescent coating to produce whitish-looking light. LEDs have a far higher ratio of short-wavelength (460 nm) blue light than incandescent, halogen, and even fluorescent bulbs, they say.
Unfortunately, the blue LED is the only LED economically practical at this time. The more balanced, multi-colored LEDs are too expensive for general use. And, because they are more energy efficent than the old heat-generating bulbs, most countries around the world have essentially mandated their use.
Not only have they been our main source of overhead lighting for the last decade or two, LEDs are used to illuminate flat screen TVs, computer screens, smartphones, and tablets — the latter two inventions having a human history of less than 10 years.
“The blue component of light is known to have merits on health when used at appropriate timing and intensity,” write the main authors of the report, Kazuo Tsubota and Megumi Hatori, both opthamologists, who worked with a team of a dozen other scientists of various specialties, including neurology, biology and physics.
Because the blue component of sunlight peaks at midday, the extensive use of LEDs, particularly into the evenings, throws off our internal clock, they say.
“Disruptions of the circadian rhythms in shift workers are known risk factors for psychiatric disorders, gastrointestinal alterations, sleep and cognitive impairments, and breast cancer,” write Tsubota and Hatori.
According to a recent study, using a tablet (e-reader) at night induces circadian phase delay and melatonin suppression, alters sleep quality, and reduces cognitive performance the subsequent morning.
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).
Because blue light has the highest photon energy, it readily penetrates through the cornea and the lens to the retina, potentially resulting in retinal damage, the ophthalmologists say.
A recent study showed blocking blue light protects mice from retinal damage. Another study found prolonged exposure to blue light with a wavelength between 400–470 nanometers can “induce severe damage to the retina,” including “total blindness.”
“The studies described above strongly suggest that light of non-natural spectrum or timing may have profound and unintended effects on … human physiology,” the authors write. “We believe it is important that our colleagues, politicians, scientists, manufacturers, and, of course, citizens realize the potential risks of excessive blue light at night on human health.”
RELATED: The Dark Side of LED Lighting