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How Color Temperature Affects Light Pollution

How Color Temperature Affects Light Pollution

Jackson at Night

Recently, there’s been a popular move in many cities and towns to retrofit their lighting with LEDs. With cheaper energy use, it seems like a no brainer. What most local governments don’t realize, however, is that there are some serious drawbacks to LED lighting if the options are not properly researched.

A Quick Overview on Color Temperature

First, let’s take a quick look at how our eyes perceive color. Our eyes are made up of rods and cones. Cones are what perceive color in daylight, and rods are our night vision, mostly transmitting information in shades of black and white. (On a separate tangent, most people in urban areas never use their rod vision anymore, a side-effect that has disastrous health consequences.) Daylight on the other hand yields the entire visible spectrum to us. The visible spectrum itself is made up of longer and shorter wavelengths that our rods and cones decipher as different colors as light hits our retinas. All the colors blended together are interpreted as white. Longer wavelengths appear warmer (reds, oranges, yellows), but confusingly, have a lower value on the Kelvin scale, the standard for measuring color temperature (1500K, 2700K, etc.). Conversely, shorter wavelengths appear cooler to the eye (greens, blues, purples). These have a higher value on the Kelvin scale, ranging from 6,500K (which would be considered a warmer-looking HD screen) to 27,000K, a clear blue sky.

White LED Streetlight

Blue is the easiest to scatter not only in the atmosphere (hence blue skies and water), but also in our eyes. It’s therefore a bit harder to make out details in blue-rich light than it is in warmer-colored lights, which is where things get interesting.

The White LED

Due to the way LEDs (and fluorescent lights for that matter) are created, white is never actually an even blend of all the colors. In fact, to create a white-appearing light, it’s required to dramatically increase the shorter-wavelengths (i.e., blue). In normal daytime use, this isn’t much of a problem. Our eyes are already adjusted to the brightness of our surroundings, so the "white" appears perfectly natural. Once day gives way to night, however, a Pandora’s box is opened up by the white LED.

  • Uphill Battle Against Evolution

    During the millions of years of our evolution, there was never prolonged white, or especially blue, light after the sun went down. Having this bright blue light glaring down on citizens throughout the night can have serious consequences on the human body (among most other animals). There’s an increasing amount of evidence confirming this that comes out practically every year. As it was described to me by Dr. Travis Longcore, we’re conducting a massive public health experiment on huge portions of our population without any kind of research or safety precautions being implemented.

  • Increased Brightness

    What many people don’t realize is that at the same wattage, white is significantly brighter than a warmer-appearing color. In fact, at the same wattage output, a white LED light will put out more than eight times more brightness (and thus, light pollution) than a warmer-looking counterpart. The side effects of this are an increase in overall light pollution (even if pointed down), adverse effects to human and wildlife health, and a huge jump in light trespass.

  • Light Trespass

    Report, after report, after report confirms that residents don’t like having daylight at night. It’s not just having daylight overpowering the night. It’s also that this light is so powerful, that it spills into bedrooms and living rooms like never before. This leads to more disturbed sleep and general dissatisfaction with the neighborhood itself. One community was kind enough to listen to its citizens’ complaints and replace the white lights with warmer ones, something we’re working with the Town of Jackson on fixing.

  • Increased Glare

    The LED streetlights are designed in such a way that you can stand underneath them and not think it’s too bright. That’s because the lights are designed to emit light horizontally rather than downward. As a result, the light actually increases glare on the roads, and thus, distracts drivers by making it harder to see the road itself, along with anything else on the road. In addition to making the streets less safe for the general public, the elderly experience glare even worse since light scatters more easily in their eyes.

Solutions to White LEDs

Help is with our Fundraiser

Shielded Lighting

Wyoming Stargazing currently has an ongoing fundraiser to help spread this kind of education and awareness. Since we’re currently working with the town and county, a donation will also have an impact in deciding how they light public areas from this point forward. We need your help though in making sure we have the funding to continue our efforts. Head to this link to help us make our streets safer by applying a more night-friendly lighting.

Warmer-Appearing LED Streetlights

LED manufacturers have also been watching these scenarios play out. Thankfully, there are now streetlights that are 3000K, much safer and healthier than the blue-intensive 6000K lights that are being installed across the country. I personally wouldn’t mind seeing them go even lower on the Kelvin scale. Flagstaff, Arizona makes great use of both warm-colored LEDs, as well as low-pressure sodium. The Flagstaff Dark Skies Coalition has an excellent series of charts showing the impact each type of light has on the sky. Based on their evidence, low pressure sodium is still the ideal choice for a streetlight, but is also a harder sell given the low-cost advantages of LED.

Shielding Lights

Adding a protective shield to ensure the light goes downward and not outward is often an easy fix. This helps the reduce the amount of light that is spreading outward, and thus, upward. Shielding also dramatically reduces glare making streets much safer for pedestrians and wildlife.

What Can You Do?

If you’re in the Jackson area, you can help us out in our fundraiser, or signup for our newsletter at the bottom of the site to get updates on our progress, as well as when we could use volunteers. Those of you elsewhere can write your local politicians letting them know your concerns for LED streetlights, while also offering them the alternatives with the reasons why they’re more appropriate. As mentioned, some places will listen to their citizens’ concerns. Plus, the more people that communicate with their local governments about the issue, the more education they’ll have, and the more pressure they’ll have to act appropriately.