LED street lighting won’t give you the blues – unless you want it to

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Contemporary life is flooded with artificial light. It’s been an inescapable fact since we moved from an agrarian way of life – where most people literally called it a night at dark – to when the industrial revolution started lighting up our cities for hours after sundown. As populations expand in urban areas and LEDs started to widely replace traditional lighting sources, some experts are questioning the impact of these changes on our health – particularly when it comes to the amount of light that light sources emit in the blue wavelengths of the visible light spectrum. Recently, LED light has been singled out as especially problematic, even though blue light is found everywhere nowadays.

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Although LED light is perfectly safe, a June 2016 report by the American Medical Association (AMA) asserts that “white LED street lighting patterns . . . could contribute to the risk of chronic disease in the populations of cities in which they have been installed.” [1] Experts at the AMA recommend “minimizing and controlling blue-rich environmental lighting by using the lowest emission of blue light possible” [2] in order to reduce potential negative effects on human health.

At the core of these assertions is the concern that some white LED street lighting emits an excessive amount of light at the blue end of the spectrum. Although glare usually results from excessive light intensity and bad optic controls, the report suggests that an excess of blue light can cause problems with glare, especially in older people. Glare can contribute to accidents, disrupt healthy sleep patterns, and possibly play a role in the development or aggravation of certain diseases such as cancer, diabetes, cardiovascular disease, and obesity. There’s also speculation that excessive light in the blue wavelengths, emitted by poorly designed luminaires, might impact animal behavior, such as the migratory instinct of certain bird species.

The AMA therefore recommends that outdoor lighting, particularly street lighting, should have a color temperature of no greater than 3000 K. Correlated color temperature (CCT) is a standard for measuring the hue of white light from a source. In general, the higher the CCT, the bluer the light. For example, outdoor light on an overcast day would be around 6500 K, while the yellow-orange hue of candlelight comes in at about 1850 K.

Despite its definitive tone, the report’s warning on the dangers of LED street lighting has sparked some controversy among lighting experts. Groups such as the National Electrical Manufacturers Association (NEMA) have gone on record with dissenting opinions. NEMA points out that the recommendation to use 3000 K or lower light only in street lighting applications “may compromise the ability of the lighting system to meet all critical design criteria for each unique application.” [3] As reported by the U.S. Department of Energy (DoE), CCT alone does not account for the potential nonvisual effects of light, which also depend on the intensity and duration of exposure: “The DoE further clarifies that an LED light source with the same CCT as a non-LED source has about the same amount of blue spectral content.” [4] The NEMA report concludes that the “recommendation for 3000 K or lower is not an appropriate solution for all applications, nor is it is supported by the current body of research.” [5]

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The Lighting Research Center (LRC) at Rensselaer Polytechnic Institute also takes issue with the report’s usage of CCT as an indicator for human health. “The CCT metric ignores nearly all of the important factors associated with light exposure (amount, duration, timing) and is only relevant to a single biological response (perceived tint of illumination),” the LRC states. “Therefore, CCT should never be used to characterize light as a stimulus for, say, blue light hazard.” The LRC believes that “it is erroneous and misleading to use a metric developed for one purpose and then apply it to another purpose, particularly with regard to the impact of light on human health.” [6]

In addition to experts’ concerns about the accuracy of the report, several media outlets paraphrased the AMA’s recommendations in a way that made the report seem inherently anti-LED. The Office of Energy Efficiency and Renewable Energy (OEERC) attempted to clarify this misconception: “Some media coverage of concerns about blue light, light at night, and dark-sky issues can give the impression that LEDs are the enemy, when in fact they’re a critical part of the solution . . . It’s important to remember that these issues have been around for decades, long before the emergence of LED technology.” [7]

An emerging focus in the lighting world today – both in industry and at research institutions – is human-centric lighting, not just in indoor spaces but also on our streets. Human-centric lighting poses several questions. How can lighting go beyond simply illuminating our spaces to concretely enhancing our lives? What effect can it have on emotional states or even our physical health? How can the right lighting boost work performance or reduce stress? 

The aim to light for human well-being and health presupposes the proper use of LED lighting technology. While the first generations of early LED replacement light modules possibly emitted more light in the blue spectrum, LED luminaires, including street lights, can be engineered to produce any color temperature or spectral profile. If a city were to choose to use only warm yellow light in residential areas, LED technology would make that choice entirely possible. 

In addition to the ability to produce any color or shade of white light, LED lighting offers additional advantages. The light beam can be easily directed and controlled so that there’s no spill light. Shields on the luminaires curtail the light even more by minimizing uplight, sidelight, and glare. For instance, it’s possible for a street to be clearly illuminated with white light while neighboring homes are kept in the shadows. This control is particularly important for supporting dark sky initiatives and to avoid unwanted light in windows. LEDs are also highly energy-efficient, particularly when combined with control systems that allow the lights to snap on only when needed – again helping to reduce light pollution.  

While most people can’t entirely escape the glow of modern life – and all the possible influences that artificial light may have on our bodies – LEDs offer an effective strategy for human health and welfare. They can be any color we wish them to be, turned off automatically when not needed, and directed to shine only where illumination is necessary. There’s no need to leave the comforts of your city dwelling to get a good night’s rest. Now, turn off your (blue light!) smartphones, laptops, and TV monitors and get some sleep!

REFERENCES

1. Human and Environmental Effects of Light Emitting Diode (LED) Community Lighting, CSAPH Report 2-A-16. Council on Science and Public Health, American Medical Association. 2016: p. 4.

2. Ibid., p. 6.

3. “NEMA Comments on American Medical Association Community Guidance: Advocating and Support for Light Pollution Control Efforts and Glare Reduction for Both Public Safety and Energy Savings.” NEMA website, 24 June 2016: https://www.nema.org/news/Pages/NEMA-Comments-on-American-Medical-Association-Community-Guidance-Advocating-and-Support-for-Light-Pollution-Control-Efforts.aspx

4. Ibid.

5. Ibid.

6. Response to the 2016 AMA Report on LED Lighting. Lighting Research Center. 30 June 2016: p. 5.

7. “Get the Facts: LED Street Lighting.” Office of Energy Efficiency & Renewable Energy website. 21 June 2016: https://energy.gov/eere/ssl/articles/get-facts-led-street-lighting

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