hank
Flashlight Enthusiast
We use several of these LED desk lights with 12v batteries for winter camping -- all now are filtered using a Rosco color filter to block the blue end, for eye protection. There's only one LED available that I know of that doesn't emit levels of blue light that (1) may damage the eye longerm, and (2) definitely reset the human body clock, which is not a smart thing to mess with.
Young folks -- read up on this. It's like your hearing, in normal living you slowly damage your eyes if you don't protect them, and you won't know what you've lost til it's gone.
Here's a source for simple plastic sheet filter material:
http://www.rosco.com/us/filters/roscolux.asp#Colors
We use these on our older LED and fluorescent lights:
http://www.rosco.com/images/filters/roscolux/310.gif
Look at the LEDmuseum spectra --- all but one 'white' LED he's checked, including the so-called warm white, have a big emissions spike in the 400-480 nm range.
For example:
http://ledmuseum.candlepower.us/sixth/v16.gif
With what I've learned recently about blue light risks, this one looks good:
Zexstar L5WWE1 # warm white
http://ledmuseum.candlepower.us/sixth/l5wwe1.gif
I'm putting them into my various older LED reading lights. I'd be very, very interested in buying new lights made with these.
Now --for those of you who haven't just turned your headphones up to 11 and quit reading (grin) -- here's why:
This blue light -- short wavelength, highest energy photons -- is associated with macular deterioration over time -- the commonest cause of blindness in older people, because the damage adds up over the years.
"whether blue light (400 to 500 nm), or all visible light (400 to 700 nm) was associated with AMD. ...established cases (AMD-4), but not milder cases, had significantly higher exposure to both blue and visible light over the preceding 20 years (Wilcoxon sign rank test, P = 0.027). There was no difference in exposure at younger ages. These data suggest that high levels of exposure to blue and visible light late in life may be important in causing AMD."
470-500 nm is the narrow band that affects the melatonin photoreceptors, that sets your circadian clock -- and that you want to block starting about five hours before you want to fall asleep.
http://www.springerlink.com/content/w57m0451647x5444/
Blue Light Special—Treating Circadian Rhythm Sleep Disorders
....subjects exposed to blue light had significantly ...
www.neuropsychiatryreviews.com/sep06/blue.html
" identifies 446-477 nm as the most potent wavelength region providing circadian input for regulating melatonin secretion. "
J Neurosci. 2001 Aug 15;21(16):6405-12.
Action spectrum for melatonin regulation in humans: evidence for a novel circadian photoreceptor.
Brainard GC, et al.
================================
"Environmental lighting powerfully suppresses the physiologic release of melatonin, which typically peaks in the middle of the night. This decreased melatonin production has been hypothesized to increase the risk of cancer. ...There is also fairly consistent indirect evidence from observational studies for an association between melatonin suppression, using night work as a surrogate, and breast cancer risk."
Photochem Photobiol. 2004 Apr;79(4):316-8.
Light at night and cancer risk.
Schernhammer E, Schulmeister K.
---------------------------------
Med Hypotheses. 2004;63(4):588-96.
Lighting for the human circadian clock: recent research indicates that lighting has become a public health issue.
Pauley SM.
"The hypothesis that the suppression of melatonin (MLT) by exposure to light at night (LAN) may be one reason for the higher rates of breast and colorectal cancers in the developed world deserves more attention. ... as a growing public health issue. Evidence now exists that indirectly links exposures to LAN to human breast and colorectal cancers in shift workers. ....
"Lighting fixtures should be designed to minimize interference with normal circadian rhythms in plants and animals ..... blue-light-sensitive retinal ganglion cell light receptors that control the circadian clock ...."
Young folks -- read up on this. It's like your hearing, in normal living you slowly damage your eyes if you don't protect them, and you won't know what you've lost til it's gone.
Here's a source for simple plastic sheet filter material:
http://www.rosco.com/us/filters/roscolux.asp#Colors
We use these on our older LED and fluorescent lights:
http://www.rosco.com/images/filters/roscolux/310.gif
Look at the LEDmuseum spectra --- all but one 'white' LED he's checked, including the so-called warm white, have a big emissions spike in the 400-480 nm range.
For example:
http://ledmuseum.candlepower.us/sixth/v16.gif
With what I've learned recently about blue light risks, this one looks good:
Zexstar L5WWE1 # warm white
http://ledmuseum.candlepower.us/sixth/l5wwe1.gif
I'm putting them into my various older LED reading lights. I'd be very, very interested in buying new lights made with these.
Now --for those of you who haven't just turned your headphones up to 11 and quit reading (grin) -- here's why:
This blue light -- short wavelength, highest energy photons -- is associated with macular deterioration over time -- the commonest cause of blindness in older people, because the damage adds up over the years.
"whether blue light (400 to 500 nm), or all visible light (400 to 700 nm) was associated with AMD. ...established cases (AMD-4), but not milder cases, had significantly higher exposure to both blue and visible light over the preceding 20 years (Wilcoxon sign rank test, P = 0.027). There was no difference in exposure at younger ages. These data suggest that high levels of exposure to blue and visible light late in life may be important in causing AMD."
470-500 nm is the narrow band that affects the melatonin photoreceptors, that sets your circadian clock -- and that you want to block starting about five hours before you want to fall asleep.
http://www.springerlink.com/content/w57m0451647x5444/
Blue Light Special—Treating Circadian Rhythm Sleep Disorders
....subjects exposed to blue light had significantly ...
www.neuropsychiatryreviews.com/sep06/blue.html
" identifies 446-477 nm as the most potent wavelength region providing circadian input for regulating melatonin secretion. "
J Neurosci. 2001 Aug 15;21(16):6405-12.
Action spectrum for melatonin regulation in humans: evidence for a novel circadian photoreceptor.
Brainard GC, et al.
================================
"Environmental lighting powerfully suppresses the physiologic release of melatonin, which typically peaks in the middle of the night. This decreased melatonin production has been hypothesized to increase the risk of cancer. ...There is also fairly consistent indirect evidence from observational studies for an association between melatonin suppression, using night work as a surrogate, and breast cancer risk."
Photochem Photobiol. 2004 Apr;79(4):316-8.
Light at night and cancer risk.
Schernhammer E, Schulmeister K.
---------------------------------
Med Hypotheses. 2004;63(4):588-96.
Lighting for the human circadian clock: recent research indicates that lighting has become a public health issue.
Pauley SM.
"The hypothesis that the suppression of melatonin (MLT) by exposure to light at night (LAN) may be one reason for the higher rates of breast and colorectal cancers in the developed world deserves more attention. ... as a growing public health issue. Evidence now exists that indirectly links exposures to LAN to human breast and colorectal cancers in shift workers. ....
"Lighting fixtures should be designed to minimize interference with normal circadian rhythms in plants and animals ..... blue-light-sensitive retinal ganglion cell light receptors that control the circadian clock ...."
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