2013-07-17
LED Lighting Poses No Blue Light Hazard
The US Department of Energy has issued a fact sheet laying out the basis for proclaiming that LED light is no more inherently dangerous than light from other sources.
A couple of months back, we discussed and largely debunked research from a Spanish team claiming to demonstrate that LED light damages human retinal cells in vitro. Now the DoE has produced a four-page fact sheet going into detail on LED light production and blue light hazard. The fact sheet does stress that all forms of lighting should meet standards for photobiological safety, but it concludes that LED light sources pose no more danger than any other lighting technology.
This conclusion will come as no surprise to anyone in the lighting industry. We can only hope that it will be more widely reported in the general press -- which, unfortunately, was quick to pick up and amplify the alarming reports of the Spanish research.
The specific hazard the DoE paper directly addresses is photoretinitis, or photochemical damage to the retina. The effect is real enough, but white-light LEDs don't trigger it in any realistic use scenario. As Soraa CTO Mike Krames pointed out in a company blog post, the exposure used by the Spanish researchers to demonstrate damage to retinal cells in a Petri dish "corresponds to staring directly into a 100-Watt-equivalent light bulb from about four inches away, for twelve hours."
As the DoE fact sheet points out, natural defense mechanisms such as looking away and blinking come into play on timescales far shorter than 12 hours.
White-light LEDs do produce some light at wavelengths corresponding to the blue part of the spectrum -- and so does every other source of white light that renders colors in an acceptable way. Phosphor-converted white LEDs start out with a blue or violet light source, but phosphors absorb and reradiate much of that light at lower frequencies. The fact sheet clarifies that LED lighting at a given color temperature, generally speaking, has no more energy in the blue spectrum than light of the same CCT generated in other ways.
Blue light, alertness, and sleep
The fact sheet does not directly address the effects of blue light (at much lower levels than what would threaten the retina) on circadian rhythms, which govern the human sleep/wake cycle, appetite, body temperature fluctuations, and more. It is well known that a blue component in light suppresses the production of melatonin -- an effect that can promote alertness in the daytime but delay the onset of sleep at night.
The developers of f.lux have compiled a great deal of accessible research on this topic on their website. This utility program adjusts the color temperature of the light produced from the screens of computers running the Macintosh or Windows operating systems. As of a recent beta release, f.lux also supports Philips Hue -- which should allow those who own this controllable lighting system to dial down the color temperature of ambient lighting, as well as the computer screen, as the evening progresses.
LED lighting won't make us go blind. But it could contribute to disrupted sleep patterns if we don't take color temperature into account. The inherent color flexibility that LED technology makes possible gives us this option.
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— Keith Dawson 
, Editor-in-Chief, All LED Lighting