Several times per year, an article—typically based on a research study—is published warning consumers about the potential health risks of exposure to blue light produced by LED lighting. The International Commission on Illumination (CIE) responded with reassurance that people are normally not at risk from general white-light sources, including LEDs. Because customers may ask electrical contractors about the so-called “blue light hazard,” ECs should be aware of the issue.
On the electromagnetic spectrum, optical radiation resides between ultraviolet and infrared radiation, with wavelengths ranging from 200 to 3,000 nanometers (nm). In turn, the visible light spectrum comprises bands of wavelengths often associated with color perception across the rainbow. “Blue,” for example, resides at around 400–500 nm, peaking at 435–440 nm. Electric white-light sources emit a combination of wavelengths at varying intensities and almost always contain some blue content, which is necessary for visual appearance and color rendering. The amount of blue content in the spectral emission is a determinant in the light source’s correlated color temperature (CCT), a metric used to describe the visual appearance of a light source and its emission.
The International Commission on Non-Ionizing Radiation Protection defines “blue light hazard” as damage to the eye’s retina caused by staring into bright light sources, such as the sun and welding arcs. The phenomenon was discovered in the 1970s. This term has more recently been appropriated to describe retinal damage and the influence on general well-being resulting from use of lighting, notably LEDs.
Why LED? The majority of white-light LED sources feature blue LEDs coated with a phosphor that converts the emission into white light. The blue pump causes a spike in light energy produced at short wavelengths, which—as one would expect—is pronounced with lamps with a higher CCT.
A number of studies have connected adverse effects with white-light sources. Most of these studies were based on unusual conditions, however, such as a very high CCT or long-term exposure to the light. For a white-light source to emit blue light at levels high enough to approach the blue light hazard exposure limit, it would have to be extremely bright—bright enough to cause discomfort glare, which triggers a natural avoidance response in people; they simply blink or turn away from it. Additionally, the portion of blue spectral content in the LED light emission is not significantly higher than traditional light sources at the same CCT, according to the U.S. Department of Energy (DOE). As for claims that blue light exposure may be linked to the risk of age-related macular degeneration, CIE called them unsupported and speculative.
According to an April 2019 position statement from CIE: “Practical assessments [of lamps] have shown that the blue light hazard exposure limits are not exceeded under all reasonably foreseeable use conditions. Furthermore, the exposure levels are often lower than experienced from viewing a blue sky.”
In a June 2013 fact sheet, DOE similarly concluded: “LED products are no more hazardous than other lighting technologies that have the same CCT. Furthermore, white-light products used in general lighting service applications are not considered a risk for blue light hazard according to current international standards.”
However, CIE cautioned against long-term, continuous exposure to optical radiation levels that approach the blue light hazard limit. While this level of exposure is unlikely with white-light general lighting, it may be possible with light sources that primarily produce blue light. An example is bright blue indicator lights in children’s toys, which should be avoided.
Though there is a relationship between blue light and circadian response, the term “blue light hazard” does not apply to it. Concerns about blue light have led the American Medical Association to recommend warmer CCTs for street lighting. These concerns also stimulated the development of new products. Some manufacturers are developing 3,000K CCT sources with suppressed spectral emission between 475 and 495 nm (“cyan gap”). One line of troffers feature a chip that switches from a blue to a violet pump at night. UL is now certifying lamps and luminaires that offer less than 2% blue content. Research by the Lighting Research Center, however, suggests that blue light has less of an impact on circadian rhythms than quantity and duration of light exposure.
Based on the CIE statement, LED lighting does not majorly contribute to blue light hazard, though circadian response to short-wavelength light will continue to be investigated, characterized and the source of evolving guidelines.