This post was written by Keith Dawson for UBM Tech’s community Web site All LED Lighting, sponsored by Philips Lumileds. It is archived here for informational purposes only because the All LED Lighting site may go dark at any time. This material is Copyright 2013-2015 by UBM Americas.


Focus on Light & Health

As if to underscore a point made by Dennis McCarthy in his piece here on Human-Centric Lighting, the news has been full of stories touching on lighting and health.

Dennis noted that most of the attention that HCL has garnered from wider circles has been about light's effects on human biology, particularly on the regulation of melatonin and the daily sleep-wake cycle. There was plenty of that in evidence this week.

DOE fact sheet
We'll start with the two-page fact sheet published by the DOE's Energy Efficiency and Renewable Energy group: Lighting for Health: LEDs in the New Age of Illumination. It is based on a recent paper in "Trends in Neurosciences," authored by "a diverse group of fourteen leading researchers" (in the DOE's words). The paper is "Measuring and Using Light in the Melanopsin Age"; both web and PDF versions of the full text are available.

The fact sheet sounds a cautionary note. While it is certain that light interacts with biology, the full contours and parameters of that interaction are not known, and can differ from person to person, and from subsystem to subsystem within the same person. quotes from a letter written by the DOE's Jim Brodrick on the fact sheet's release:

Recent research has greatly advanced our understanding that light not only enables vision, but is also a critical signal to our biological systems, affecting circadian rhythms, pupillary response, alertness, and more. However, applying early research findings to widespread lighting practices must be done with great caution, if it's ready to be done at all.

Computer devices and sleep
The Guardian ran a piece by Richard Wiseman (author of Night School): "Log off before you nod off: why a good sleep is vital for a long life." It summarizes some of the research suggesting that the blue light from computer screens, smartphones, and tablets is behind "a sleeplessness epidemic linked to diabetes, heart disease -- and an early death," in the perhaps overly dramatic words of the Guardian. Wiseman recommends wearing amber-tinted glasses if using electronic devices in the hours before sleep.

High-CCT street lights
A campaigner in the UK, Simon Nicholas, has succeeded in getting the local council to postpone installing high-CCT LED replacement street lights. Nicholas points to research indicating that the 4000K or 5700K light from the sorts of LED-based fixtures most often installed can disrupt sleep and bring on health issues. He contends that in the scramble to save energy and money, cities are installing lights with too much blue in them. The BBC hosts a video Nicholas made, along with a somewhat acrimonious debate staged with an elected official and a dark-sky campaigner.

I looked online for low-CCT choices for street lighting, and did not find much. For example, Cree's street lighting products are all 4000K or 5700K. The city of Los Angeles specified 4000K in their recent replacement of 140,000 street lights. In 2011, researchers at CMU did a study ahead of the city of Pittsburgh's street light replacement project, and recommended a CCT of 3500K, with the lights adjustable down to a CCT of 2700K. As far as I can learn online, the city seems to have asked for bids on lights at 4700K and 5200K.

One-trick bulb
There has been a fair amount of coverage of the Drift Light, a bulb from a Utah company called Saffron. It dims over 37 minutes to provide a simulation of descending nightfall. It is controlled by an ordinary light switch: one click to turn it on normally, two to initiate the dimming sequence, and three to stop the dimming at a low level of illumination as a night light. The bulb has a CCT of 2700K that does not change as it dims. It costs $29 from the company's website.

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