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The LED Blues

Oct. 20, 2016
American Medical Association report stirs up growing debate over whether blue-heavy LED street lighting is a bright move. Is 3,000K part of the answer?

A summer of white-hot debate over the advisability of relying on the prevailing technology for bright white, high-intensity LED street lighting has merged into an autumn of a cold standoff. In one corner, the American Medical Association (AMA) has yet to formally respond to critiques of its controversial report (issued in June), linking the growing prevalence of established LED lighting solutions to heightened risks to human well-being and the integrity of the natural environment.

The American Medical Association has called for “proper attention to optimal design and engineering features...that minimize detrimental health and environmental effects (Joe Christensen/iStock/Thinkstock).

Its new stance, stated in the report, is that “communities considering conversion to energy-efficient LED street lighting use lower CCT lights that will minimize potential health effects,” and, focus on “minimizing and controlling blue-rich environmental lighting by using the lowest emission of blue light possible to reduce glare.” Furthermore, all such lighting “should be properly shielded to minimize glare and detrimental human and environmental effects,” and “consideration should be given to utilize the ability of LED lighting to be dimmed for off-peak time periods.”

On the other side of the debate, those who quickly challenged the report and its characterization in the media have continued to sharpen their attacks as the report influences decision-making. They insist the core of its conclusions and recommendations is wrong, or, at best, ripe for costly and distracting misinterpretation. (EC&M attempted to reach AMA for comment; it was unsuccessful.)

Caught in the middle are those evaluating options for LED street lighting conversion projects (see AMA Report Lands Amidst Reviews, Reconsideration of LED Lighting).

The report, from AMA’s Council on Science and Public Health, pumped fresh life into a long-simmering debate — whether blue wavelength light does, at some threshold in the environment, trigger bodily responses such as suppression of the hormone melatonin and disruption of circadian rhythms.

Studies have linked decreased melatonin to sleep deprivation, obesity, and other maladies, including cardiovascular disease and cancer. Citing numerous reports and studies, some from a decade ago, it recaps the potential health dangers that excessive nighttime blue light exposure carries, as well as more benign implications for night sky viewing, singling out more prolific LED outdoor lighting as a leading culprit. But it also expresses support for switching to LED technology to realize savings in energy costs and decreased reliance on fossil fuels, but only if the conversion is “proper.”

Defining the cure

Where the report comes in for criticism is mainly in its prescription; essentially it’s characterization of “proper.” Generally, AMA is now recommending that more care be taken to select white LED outdoor lighting solutions that minimize the production, scatter, and glare of blue light. The most direct way to achieve that, it says, is to install “warmer” LED lighting than is currently the standard, specifically that with a correlated color temperature (CCT) index of 3,000K or lower — a Kelvin rating that produces a lower, presumably more acceptable, level of blue light that may also minimize melatonin suppression. Additionally, the report recommends that all LED lighting should be shielded to reduce glare and also be dimmed when possible.

In a press release accompanying the report, AMA said the aim was to provide guidance for the growing number of
communities considering options for converting street and area lighting to LED. AMA board member Maya Babu was quoted as saying the report was crafted to encourage “proper attention to optimal design and engineering features when converting to LED that minimize detrimental health and environmental effects.”

In communities where LED streetlight conversion plans are well underway, the American Medical Association report casts a shadow on future work (Copyright Ethan Miller, Getty Images).

Critics, though, say AMA has strayed from its area of expertise, proposing simplistic solutions that fail to grasp the nuances of light and the many variables that determine its sensory impact. In training its focus on CCT grades, the report takes a decidedly narrow approach and also overlooks other sources of blue light in the environment. Moreover, they contend it doesn’t sufficiently acknowledge the offsetting and unique qualities that LED technology offers in the area of controlling light’s intensity, direction, pattern, timing, and even color spectrum — all of which directly affect and determine retinal light exposure.

The report’s prescription for 3,000K or lower LED lighting lands in critics’ crosshairs, partly because it’s not the current industry standard of 4,000K. The consensus from an array of experts evaluating the recommendation is that CCT values are only one way of assessing how much blue light a light source will emit. They point out that it’s only useful as a relative measure of the spectral content of a light source and shouldn’t be used in isolation to rate blue light exposure.

Fixating on CCT

“The recommendation to go to 3,000K is utter nonsense,” says Mark Rea, director of the Lighting Research Center at Rensselaer Polytechnic Institute, Troy, N.Y., who co-authored a swift and pointed response to the report for the LRC. “It demonstrates a lack of understanding of the science of light, and ignores other factors that come into play, such as the amount, duration, and timing of exposure. Taking a narrow view of one design criterion at the expense of others doesn’t sound like a completely good response to the issue.”

In the RPI paper, Rea and co-author Mariana Figueiro emphasize that CCT is useful only as a measure of the perceived tint of light along a spectrum. It’s only one component of the spectral power distribution (SPD) of light, a broader measure that accounts for other metrics that predict a potential stimulus response. “CCT should never be used to characterize light as a stimulus for, say, blue light hazard,” they write.

Because the body’s response to blue light depends on other factors independent of its relative color temperature, the paper notes that 3,000K isn’t a magical number in evaluating LED lighting options. Factoring in a light source’s full SPD can mean that a 3,500K light source could conceivably produce greater melatonin suppression than a 5,000K source.

In recommending 3,000K, the AMA study also links a lower CCT to other sensory considerations. Stating that 3,000K light has about 21% of its emission in the “blue-appearing” part of the spectrum, lower than the 29% for widely installed 4,000K, AMA says the difference translates to the former being notably less harsh. With 3,000K lighting, the report says discomfort and “disability glare” linked to the point-source nature of LED lighting could be proportionately reduced. “This emission is still very blue for the nighttime environment, but a significant improvement over 4,000K.”

Critics, though, argue the difference is not enough on its own to justify a wholesale and potentially costly shift to 3,000K. One such critic, Bruce Kinzey, director of the U.S. Department of Energy’s (DOE) Municipal Solid State Street Lighting Consortium (MSSLC), and senior research engineer at Pacific Northwest National Laboratory, cites statistics that show a large overlap in melanopic contents of 3,000K and 4,000K LED lights. With respect to glare, Rea and others note that it’s not a function of spectral content as much as it is of optics and the amount of light entering the eye. Switching to lower CCT lighting on the basis of color temperature alone is misguided — even more so when there’s no clear difference in impact on either score, says Kinzey.

“Sales of 3,000K LEDs are still pretty small; not all suppliers even offer it,” he says. “These products often carry a higher price tag, and they might use more energy, so total operating costs might be higher.”

Understanding trade-offs

Even if a move to warmer LED lighting to reduce blue content could be justified and done economically, doing so could reduce the substantial visibility benefits that LED lighting offers. A consequence of ratcheting down from 4,000K, lighting experts say, is that the security and safety benefits stemming from sharper clarity of illuminated objects could be compromised. That could dilute one of the justifications for steadily replacing traditional high-pressure sodium (HPS) lights and their yellower cast with white LED lighting.

Proper design technologies can effectively address glare and harshness complaints that may arise with LED streetlighting conversion projects (Apriori1/iStock/Thinkstock).

AMA’s report says LED lighting designers should consider the public safety factor, but points out that poor designs that fail to properly shield and direct LED light can negate the sought-after benefits of brighter light by increasing glare and decreasing visual acuity. “This leads to worse vision than if the light never existed at all, defeating the purpose of the lighting fixture.”

But in a published response to AMA, Jim Brodrick, DOE’s manager of solid-state lighting technology in the Office of Energy Efficiency and Renewable Energy, suggested moving back in the direction of low CCT products like the 2,200K of HPS lighting would be a mistake.

“For security and other visibility reasons, you want light where colors can be seen better,” he says. “Low CCTs may be beneficial for reducing non-visual impacts, but they may also reduce the effectiveness of lighting.”

White LED lighting in the widely deployed 4,000K range may not be able to compete with the warmth and minimal blue content of HPS lighting, but neither can 3,000K lighting, lighting experts say. More importantly, and what the AMA report may not acknowledge with its reference to “poor designs,” is that LED technology and fixture architecture extend much more control to lighting, enabling it to be finely shaped, directed, shielded, and dimmed — potentially even on demand. That can effectively address many of the glare, harshness, and blue light-exposure issues that may come with bright-white LED lighting products, positioning LED as the answer to a host of lighting challenges rather than the cause.

“We don’t feel like they’re (AMA) reflecting the situation accurately,” says Kinzey. “Our position is that LEDs offer flexibility in that light can be directed and shaped to the target, and routinely do so using half or fewer lumens than the original lamps. Despite great skill in reshaping the light output of conventional lamps using reflectors and optics, it’s never perfect, and stray light and more lumens than needed are the result. These demonstrably improved capabilities mean that LEDS aren’t the problem; they’re part of the solution. I don’t think the AMA would disagree with this perspective, but it’s a message that is getting lost in the current media coverage.”

Adaptability in action

A recent Cambridge, Mass., conversion is offered as a textbook case for how LED lighting can be managed. In the MSSLC response paper, Kinzey explains how dimming controls included in the city’s 4,000K LED street lighting conversion in 2013 reduce energy usage and light output. The wireless dimming system turns on the lights at 70% of maximum output at dusk, and then at 10 p.m. dims them down further to 35% of maximum. The dimmed lights, in turn, lower the overall amount of blue light radiated, offsetting the higher melanopic content of the 4,000K lighting system, pegged at around 3.4 times that of the HPS system it replaced.

Glenn Heinmiller, principal at Lam Partners, a Cambridge company that designed the system, says its dimming feature was selected to address light pollution and energy usage, and that blue light mitigation might be a side benefit. And it illustrates the point that blue light doesn’t have a fixed value in real-world LED applications, he adds. The takeaway should be that CCT values are a relatively minor concern.

“All of the focus on wavelength and color temperature distracts from things people should be doing, like dimming for later at night, saving energy, and reducing light trespass,” he says, adding that a close read of the AMA’s report shows it reveals little new information about blue light or LED technology and that the media misconstrued its conclusions. “There’s no magic bullet for reducing blue light, and it’s not necessarily a bullet at all to go from 4,000K to 3,000K.”

But aside from offering prescriptions critics say are suspect, the AMA report’s characterization of the blue light problem — and LED’s overall contribution — draws some fire. Reviewers say there’s still lively debate about how blue light is biologically processed and its true environmental impact, and that it’s nevertheless unreasonable to single out street lights in a world filled with blue-light emitting screens and other interior sources, often at much higher intensity. On balance, many say, properly designed LED lighting is a net positive in a world dependent upon night lighting, but also increasingly and rightly sensitive to its mix of potential side effects.

Kinzey, pointing to the recent discovery of non-visual receptors in the human eye that may process blue light, says our understanding of blue light is evolving. Given that fact — and the knowledge that LED is accepted technology that can actually be tailored to minimize blue light — he says declarations as pointed as the AMA’s are probably not warranted.

“We’re not saying there’s nothing to the AMA report, just that there’s a lot of it that remains to be established,” he says. “And this is not a problem unique to LED lighting; all broad-spectrum lighting sources produce some blue light.

 “The AMA report and ensuing recommendations are based on a lot of speculation and incomplete research findings. We are engaged in current efforts to better quantify some of the relevant underlying numbers and thereby improve the quality of information available to both the research community and the general public,” he says.   

Zind is a freelance writer based in Lee’s Summit, Mo. He can be reached at [email protected].

SIDEBAR: AMA Report Lands Amidst Reviews, Reconsideration of LED Lighting

Its conclusions are being challenged, but the American Medical Association’s (AMA’s) prescription to install warmer LED street lighting with less blue content is nevertheless influencing consideration of plans to convert to LED lighting.

In some communities where conversion plans are in various stages of initial development or even reassessment, the June AMA report on the impact of LED blue light on health has been injected into a debate that was already lively.

“We’ve gotten some inquiries, questions about lighting systems that have been installed, that were in design and were out for pre-bid, wanting to discuss whether they should make a switch,” says Paul Lutkevich, technical director and lighting specialist at WSP/Parsons Brinckerhoff, a Boston-based international engineering firm that has designed LED lighting systems for communities.

In Washington, Steve Gorcester, director of the state Transportation Improvement Board that is working to help more than 200 cities fund transition to LED street lighting, says AMA’s recommendations are a fresh consideration. “After the AMA report, we’ve had more questions about color temperature, a few more instances where people who’ve been researching LED and pulling up information on ‘dark sky’ recommendations now have seen the AMA report,” he says. “Some communities are asking more questions about what’s getting installed.”

That was happening well before AMA issued its report; complaints about the brightness of LED lighting, its impact on night sky visibility, and well-documented concerns about blue light contributed to reviews of plans and, in some cases, changes. Some cities in Florida, California, Massachusetts, and Arizona changed course and decided to install less intense LED street lighting after hearing complaints and reviewing research. Others, including New York and Seattle, considered backpedaling on LED brightness, but ultimately didn’t. Some, like Phoenix, are in limbo, seeking new bids on less-intense lighting after weighing concerns, testing various alternatives, and soliciting feedback from citizens.

But the AMA report, coming from a respected authority, could change the debate’s dynamics. Reiterating the potential dangers of blue light exposure and specifying 3,000K-range lighting with less blue content, the report might have a “doctor’s orders” feel to it that could influence some decision makers.

Yet lighting experts and others advising communities on LED conversion programs counsel a big-picture approach. Lutkevich says he’s reminding concerned clients that blue light dangers are not fully understood, a direct link between LED street lighting and overall blue light in the environment is tenuous, and that a change in spectral content can mean a reduction in visibility.

“Some who’ve said they’re inclined to switch the CCT level are doing so without knowing what the real impact will be,” he says. “We’re telling them we wouldn’t reduce it because it could create roadway visibility issues. It’s not changing our recommendation to stick with standard 4,000K lighting — and to use adaptive lighting controls and stringent optical controls to reduce light trespass and sky glow.”

On the heels of the AMA report, Gorcester says his group is not taking a stance on it, but is advising communities to factor in AMA’s recommendations along with relevant information about LED lighting options. That’s leading to a few more cities testing various options and some to specify 3,000K or lower lighting.

“Our formal position is we want them to be aware of the AMA recommendations and the dark sky issues and then to make an informed decision about what color temperature to use,” he says. “But the other factor to consider is that manufacturer conversion to warmer temperature LED lighting is just now occurring, so the state of that transition and availability comes into play.”

About the Author

Tom Zind | Freelance Writer

Zind is a freelance writer based in Lee’s Summit, Mo. He can be reached at [email protected].

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