When the American Medical Association released its report on human and environmental effects of LED streetlighting this past summer, it sparked some alarmist headlines: “Doctors issue warning about LED streetlights” and “Are streetlights damaging YOUR health?” Immediately, concerned citizens began asking questions of their utilities, municipalities and outdoor lighting manufacturers.
The AMA has shone a light on streetlighting: an industry in flux. And some municipalities are halting and re-examining their relighting initiatives. “Despite the longstanding nature of these issues – they’ve been around since electric lighting was invented – there seems to be this association formed in the public mind that these are inherent in LEDs. It’s because of the timing, I think, the fact that we’re learning all about these issues at the same time that LEDs are really taking over,” said Bruce Kinzey, director of the US Department of Energy Municipal Solid‑State Street Lighting Consortium. “We’re going to work to try to convince people that LEDs are not the source of the problem, that they are part of the solution.”
The lighting industry was quick to react, attempting to calm fears by touting the advantages of LED streetlighting and calling into question both the conclusions and recommendations of the report. The complete AMA report does cover the panoply of LED’s advantages in outdoor lighting: cutoff, efficacy, controllability, longevity. But the report emphasizes the health effects of the “excessive blue spectrum,” and offers a one‑size-fits‑all recommendation for warm color temperatures.
The AMA supports streetlight conversion, but recommends 3000K or lower LED lighting (with about 21 percent [or lower] of emissions in the blue wavelengths) over 4000K LEDs (at about 29 percent). A third recommendation – given short shrift in the press – points out the importance of cutoff and dimming.
The National Electrical Manufacturers Association (NEMA) emphasized this third recommendation to support LED. LED exceeds the ability of any other light source to put light where you want it, when you want it, in the amount you want. The tiny size and digital nature of LED offer unparalleled advantages in light distribution and cutoff, plus dimmability combined with timers. Spectrum can be adjusted, somewhat, by carefully selecting phosphors. Real‑time spectral tuning, using lighting controls, is not yet cost‑effective.
The AMA report includes glare in its indictment of excessive blue spectrum. Both disability glare (a veiling luminance that interferes with seeing) and discomfort glare (which causes an uncomfortable or even painful sensation in the eyes) have the potential to increase risks for motorists and pedestrians. Disability glare is not affected by different white‑light spectra; though discomfort glare is exacerbated by bluer wavelengths. But controlling the amount and distribution of light are more impactful in both types of glare, according to the Lighting Research Center’s highly technical response.
In the conversion from predominantly HPS streetlighting to white‑light LED, dark sky advocates have criticized high‑CCT LEDs. Indeed, bluer wavelengths do scatter more in the atmosphere, exacerbating skyglow. Some wildlife, particularly insects, are more disrupted by shorter wavelengths.
Because LED sources are very luminous and very tiny, they can present glare. But this tiny profile also allows precise beampatterns and sharp cutoff in well designed luminaires and installations. Good design can limit both kinds of glare plus light pollution – i.e., upward light that can scatter and create widespread skyglow – and light trespass – i.e., lighting shining into residential windows or wildlife areas where it is unwanted. Some newer products can be made to order with computer-generated distributions for a custom light footprint and cutoff.
LED has greater potential for more subtle lighting strategies using unobtrusive lighting instruments. Beyond energy and maintenance savings, streetlighting upgrades present opportunities for improving lighting quality, which can enhance enjoyment of public spaces and public safety.
Few complaints in Seattle
Edward Smalley oversees Emerging Technology Services for the Customer Energy Solutions (CES) division of Seattle City Light. Seattle is about three‑quarters through converting 85,000 streetlights to LED. “We were able to address lighting trespass with adjustments, very specific adjustments in how the luminaire is manufactured. Because City of Seattle was one of the earlier adopters, we were able to work directly with the manufacturers on how they distributed light.
“HPS lighting throughout the city was always, for the past 25‑30 years, washing the sides of houses. When we put in the same distribution pattern with LED, as an example, we found that that bluer color temperature was not welcome.” Numerous pilot tests led the city to a much narrower beam pattern that focuses lighting along the streets. Where odd configurations, like hills, lead to trespass, a house‑side shield is added to the offending luminaire.
Many years ago Smalley participated in Seattle’s conversion from mercury vapor to HPS. That experience led the department to expect about 20 percent of the new lights would elicit a customer complaint: that’s 10,000 complaints expected. He said that number is under 4 percent so far. He attributes the project’s success to work on mock‑ups and customer surveys, which he recommends for cities large and small. Seattle streetlights are about 4100K.
White-light LEDs also allowed Seattle to drastically reduce light levels. “Not only did we reduce the uplight [with full‑cutoff luminaires], we also purchased luminaires that produce quite a percentage less illumination in general.” The white‑light solution appears brighter and it’s likely that the improved color and color rendering aid in detecting contrasts, of pedestrians and other obstacles.
“With LED we could choose quality lighting, we could choose better maintenance and we could choose putting the light exactly where we needed to. Previously, we just could not do all of those three primary things,” Smalley said.
Layering dimming controls can cut lumens, and therefore blue content, even further. In a presentation to the Illuminating Engineering Society’s 2016 Street and Area Lighting Conference, Kinzey cited the LED streetlighting conversion in Cambridge, MA, where installed lumens, across the city, dropped 41 percent. At 4000K the white‑light LED system installed did increase “blue” lumens tremendously, compared to HPS. But because the system dims down to 70 percent output at dusk and later down to 35 percent, blue lumens are actually reduced 34 percent (compared to HPS) from midnight until morning. “LEDs have the ability to address these issues like no other product that’s come before,” he said.
Why are they picking on LED?
The DOE’s initial response questioned why AMA is picking on LED streetlighting. Blue light is blue light, whether it’s coming from the halogen lamp in your hallway, your television or cellphone, or a streetlight across the yard. The implications for health effects apply to all light sources. Yes, it’s true that for all light sources, blue light content increases as CCT increases.
Most research on the nonvisual effects of electric lighting (besides thermal effects, photosensitivity and retinal damage) has focused on melanopic content, that is the potential for light to suppress melatonin production and therefore disrupt circadian patterns of sleep and wakefulness. “LEDs are the same as any other light source at relatively the same color temperature. They have the same kinds of melanopic content in them,” said Kinzey. Again, the AMA report recommends 3000K LED lighting, with about 21 percent of emissions in the blue wavelengths, over 4000K LEDs, at about 29 percent. Kinzey cites the blue content of 4000K fluorescent and metal halide at 30 to 35 percent.
The Lighting Research Center critiqued the science of the AMA conclusions and recommendations. In addition to spectral content, human biological systems respond to the intensity of illumination and duration of exposure. (Timing of exposure is also important, but we’ll just consider nighttime exposure here.) And it’s not just the wavelengths where white‑light LEDs tend to spike that are photobiologically activating. LRC called for further research on the effects of long-wavelength light on circadian disruption, beyond just melatonin suppression. In addition, LRC criticized the use of CCT as a “short‑hand metric” to predict health effects.
“If it turns out that this is a serious issue and we need to address it, then we need to understand what the contributions are for these other sources as well.” Kinzey considers lighting at home, TVs and personal electronics, interior and exterior commercial lighting, vehicular lighting, even the luminance of the book we read at bedtime. “We know that there’s lots of other interior sources. So where does the streetlighting – that little trickle of light coming in from the bedroom window – how does that compare in the overall context?” These questions add to the current uncertainties around circadian effects.
The lighting industry has not questioned the right or the responsibility of the AMA to raise the issues of blue light, circadian disruption and health. But the research is still emerging on both what characteristics of light and exposure might have potential health effects and what exactly those health effects might be. Many industry players, from the IES to Eaton, have expressed interest in working with the AMA on future recommendations that emphasize careful design. A few have welcomed the attention on how good lighting can be, and just how bad most streetlighting strategies currently are.
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