Dark Sky Initiative

A Bright Solution to Light Pollution

LEDs: Not the Answer to Eye and Environmentally Friendly Lighting

The following is a post provided by a fellow amateur astronomer, Francis Parnell, an uncompromising, true-blue, light-blight fighter.

While LEDs (Light Emitting Diodes) are quickly becoming the way to light the 21st century, research has shown that there’s a “dark side” to this new type of lighting.

Due to their present design, the popular 3000K to 6500K (Kelvin) LEDs that are being installed all across the country are causing many problems because this White Light (Blue-Rich White Light) is loaded with short wavelength blue and green light, which have much higher environmental impacts.  These short wavelengths are detrimental to us, nocturnal mammals, reptiles, insects, amphibians, and the nighttime environment as a whole.

Our eyes perceive this blue component as being 3 to 5 times more intense and glary than the yellow-orange High Pressure Sodium (HPS) lights that we’re used to seeing at night.  It scatters more in our eyes crating a “veiling” effect making it more difficult to see our surroundings at night.  For older drivers and those with impaired vision this can be a dangerous situation.  Our visual system responds well to white light in the daytime, but not at night!

Our dark-adapted (nighttime) eyes are much more sensitive to the shorter (bluer) wavelengths than light adapted (daytime) eyes. Light sources producing more blue light will appear many times brighter (more glary) to our dark-adapted eyes.

Even without changing the amount of light or shielding, switching a lighting installation from High Pressure Sodium to 4100K LEDs will increase sky glow as if the amount of HPS lighting had been increased by 170%, or nearly tripled.  And research in Australia has shown that compared to other types of lights at night such as High Pressure Sodium and Low Pressure Sodium, LEDs attract 48% more insects — LEDs are an insect death trap — that suck the insects completely out of the environment.  Even our old familiar incandescent bulbs weren’t this bad!  For both humans and all nocturnal creatures, the one thing we shouldn’t do when it comes to light at night is to turn it into a “White-Light” night.

The best type of lamp to use for outdoor lighting at night is HPS, as it causes the least environmental impact.  Compared to “blue-rich” LEDs, the glare in our eyes will have lots less impact, too!

Correlated Color Temperature (CCT) is a number used by lighting companies to identify the “perceived color” given off by light sources and is measured in degrees Kelvin (K).  But it is not an accurate way to determine the actual amount of blue and green from any light bulb (lamp) or LED.  CCT is a very crude way to describe how “warm” or “cool” a light appears to the human visual system.  Lower temperature CCT tends to look “warmer” and more eye friendly while higher temperature CCT numbers appear “colder” and harsher to our eyes.

There’s a saying that “The world runs on perception an not on reality.”  Across the country city / county leaders are rushing to install LEDs without any knowledge of outdoor lighting — LED lighting especially — and the complaints from citizens have been very vocal.

With all of the extensive research done in Europe and the U. S. in the last few years, it’s imperative community leaders find out about this new type of lighting before making decisions that will last for 30 years or more and cost lots of money!  Community leaders need to go with the research and not the “sales pitch” from the local utility — whose only real purpose is to sell more and brighter light — and instead go with the facts and what peoples’ eyes tell them, not irrational perceptions.  Turning our cities and towns into Perpetual Daylight would be the worst decision leaders could ever make.

The complaints from citizens in some cities where blue-rich LED lights have been installed have been heard by the local Powers-That-Be.  Some lighting companies are beginning to address the “blue-rich” problem.  But the best thing for leaders to do is wait until the lighting companies get the problem corrected and solved before spending huge sums of taxpayer money.

In December of 2014, General Electric published a White Paper on the problems with “Blue-rich” LED lighting.  And at the American Medial Association (AMA) meeting in June of 2016, the delegates voted unanimously to support “getting the blue” out of LEDs.

Best for light pollution reduction:  (1) Narrow-Band Amber LEDs (NBALED) with a narrow-spectrum yellow-orange, which are almost equal to LPS in light pollution reduction.   (2) Phosphor-Converted Amber, which is similar to HPS lights.  (3) LEDs at 2400K, a warm white LED with little blue included, which so far has not seen wide use.  (4) FLED Filtered LEDs, which remove wavelengths of light less than 500nm (nanometers).

For the latest research on the problems with LEDs go to Flagstaff Dark Skies Coalition and their Facebook page; and the Illinois Coalition for Responsible Outdoor Lighting (ICROL) and their Facebook page.


  1. Francis,
    I liked the post. Our company is the one that deployed the FLED systems in Hawaii. We have made some progress on the non filtered LEDs also with our first 2000K (again, non filtered) engines. Let me know if you would like any of the data on our technology.


  2. The International Dark-Sky Association (IDA) published a press release in 2009 and a white paper in 2010 warning against the blue-rich LED lighting. Other than the American Medical Association (AMA), who listened and supported IDA’s findings, the lighting industry and the US Department of Energy ignored the concerns and hastily proceeded to force blue-rich LED’s into the marketplace. Among the few companies who listened were Eric’s – but now, thanks to the AMA, everyone is listening and offering products. The International Astronomical Union (IAU) recommends first, FULLY SHIELDED LIGHTING. Second, reduce the total light in the environment. Third, use a better spectrum, as discussed here. Do all three, and a far better result will be had.

  3. LEDs will certainly save energy but the present generation of luminaires being deployed around the world are awful. The only way to rectify this problem is to use low colour temperature amber LEDs that will cast a glow similar to the old SOX lighting. All lighting should be 45 degree full cut-off to minimise light intrusion onto properties. I would further contend that rural areas should never be lit up unless there is an absolute need due to a serious, recognised hazard. In addition, in residential and suburban areas, the lights should be motion operated and subject to an 11p.m. till dawn curfew. There is no point in keeping lights on when no-one is around. Dimming is not an option. Why dim lights when they can be switched off altogether? Yet they won’t bite the bullet and implement these recommendations, which are the most sensible and obvious way forward. The financial savings and environmental benefits will then be enormous. As things stand at the moment the standards implemented by the lighting community are all wrong and this needs to be rectified to include recommendations outlined above. They should also respect householders who don’t want lighting affecting their properties. If a municipality is told to remove obtrusive lighting from outside a property they should not prevaricate with arguments about spacing, etc., but simply send an engineer down to the property and get rid of it.

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