Just as we are head towards the dark months of the year, this article from the Washington Post provides background on the American Medical Association’s warning that streetlights — such as those in Seattle, Los Angeles, New York, Houston and elsewhere — emit unseen blue light that can disturb sleep rhythms and possibly increase the risk of serious health conditions, including cancer and cardiovascular disease. The AMA also cautioned that those light-emitting-diode lights can impair nighttime driving vision.
Everyone is on the LED bandwagon, including the street lighting in many metro municipalities. The City of Surrey is spending 11 million dollars on upgrading street lighting to LED, with an expected energy savings of 1 million dollars a year. Surrey will be one of the first municipalities to be completely converted to this new light technology.
Know to be cost efficient these lights last 15 to 20 years, not two to five like the previous high-pressure sodium street lamps, and the light is spread more evenly. New York City has responded by using a bulb with less intensity for street lighting intensity bulb that the AMA considers safe.
There was an early Federal push in the USA to adapt to and use LED lighting, and it appears the higher intensity of these earlier lights are the problem. Lighting is measured by color temperature, which is expressed in “kelvin,” or “K.” The original LED streetlights had temperatures of at least 4000K, which produces a bright white light with a high content of unseen blue light.
Now, LEDs are available with lower kelvin ratings and roughly the same energy efficiency as those with higher ratings. They don’t emit as much potentially harmful blue light, and they produce a softer amber hue.
Researchers have indicated that blue-rich outdoor lights may decrease the hormone melatonin which balances sleep and regulated the body’s circadian rhythm of the sleep and awake cycle. Researchers note that the real challenge may be that humans have not evolved to see light at night. The AMA also expressed concern on the impact of this light on wildlife, animals and birds.
It’s an example of the early adoption and embracing of a new technological improvement without rigorous testing of potential health impacts on human as well as other animal and bird life.
intensity =/= kelvin
“it appears the higher intensity of these earlier lights are the problem”
these would be appropriate terms:
higher frequency
higher color temperature
higher energy photons
higher intensity simply means brighter light, which for an incandescent would mean a higher color temperature, but for LED means simply a brighter light, as there is no appreciable shift in color temperature as intensity changes.
I think it all depends on the particular light fixture and how well it was designed and manufactured.
White LEDs work by actually being a blue and ultraviolet LED shining onto a phosphor, (much like fluorescent lights) and that phosphor shines white light. There needs to be a UV filter to prevent UV from shining out. This UV is what’s bad. If a fixture is well made there’s no problem. If you go cheap then there might be manufacturing (or design) problems allowing it to leak out.
For the most part streets with LED lighting tend to be nicer to be on. You have to make sure you get well made ones though.
This isn’t a case of “early adoption without adequate testing.” LEDs are very well understood. Here’s some basic background information.
First, the negative effects of any type of light is always a function of exposure, and our exposure to street lighting is very very low by comparison to lights at home, many of which are now LED as well (4 lux under a streetlight vs 60 lux under a potlight at home, to give a rough idea.) Street lights only look bright because we see them against a dark background. In addition, the length of our exposure to street lights is very low, even if we drive a lot, because street lighting is intermittent, even if it looks even to us (in fact, street light brightness is only 4 lux or above when you’re near the light and everything in between is extremely lowly lit.) So exposure to LED streetlights is a tiny issue.
Second, colour is a big issue but not because some lights are on the blue end of the spectrum and dangerous to our eyes / brains. Roads are safer when people see better. Any street light with an extreme colour cast (like the blue of a mercury vapour lamp or the orange of a sodium vapour lamp) makes it more difficult to see colour well so it’s harder for people to register what they are seeing, particularly small things like people crossing the street. If you look at the picture in this article, the LED side of the picture is obviously better for that. Also, the better the colour range of the light, the less light you need to see as well, so eventually we can expect that LED street lights with what is called a “high Color Rendering Index” will be able to be even less bright than conventional street lights are today, which will help us with other things we’re trying to get, like “darker skies.”
It is true that the white LEDs are great visibility, but only in the directly lit areas. If you look at the yellow side, you see areas by the side of the road much better where people or animals might be hiding as well as the road itself. If the lights were farther apart, you would see the darker areas between the lights better with a warmer light color. This is because blue light stops down the pupils to the max and the strong contrast and scattering create glare which obscures darker areas. Aside from the health problems, this is why a compromise color of warm white, about half way between the old lights and the new, is the best of all worlds: excellent visibility, good enough color rendition, and much better comfort for drivers and homeowners.
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Reblogged this on Sandy James Planner.
Because they aren’t. Some early ones put out too much blue. That’s been fixed.