Are LED Streetlights Causing You Problems?
Walking around at night, are your eyes more easily bothered by the streetlights? There’s a reason for that.
LED streetlights have recently become more popular across the U.S. These are more efficient, last longer, and save municipalities money when compared to older bulbs, but they also have their negatives. This influx has prompted the American Medical Association, or AMA, to release an official statement, unanimously approved by the group’s members, with guidelines on how to mitigate the potential for harm to both human health and the environment.
The main problem with them is their color temperature (CT), a numerical rating of the color hue of a light source. Higher values indicate more blue content and “cooler” lights while lower values indicate a “warmer” light with more red content. The AMA advises that outdoor night lighting should not have a CT over 3,000 Kelvin; a white LED light, popular in cities like Seattle and New York, can have a CT of 4,000-5,000K. For reference, a typical incandescent bulb is about 2,700K and a candle or small fire is around 1,800K. These LEDs do not just affect circadian rhythms but may also harm the human retina if viewed for a long enough period of time. Driving at night could soon become much more difficult due to this effect.
Another issue is that while CT is a useful metric, it has its limitations, namely, it does not factor in human color perception. Correlated color temperature (CCT) is another method that accounts for how human vision is sensitive to colors. Going by this method, two LEDs with a CT of 3,000K may look vastly different from each other. One light may have more blue content than the other which would cause a shift in their hue. While the AMA’s statement is a start, this example shows that CT or CCT measurements alone are inadequate and additional metrics are needed.
How can an organization or city be sure that their LEDs are not damaging? Konica Minolta Sensing Americas has a wide array of light measuring tools that can help. Both the CL-200A and the CL-70F can measure color temperature along with other metrics like duv or spectral power distribution (SPD) that help determine your streetlights are emitting blue content within a safe range.
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