Lighting Issues–Technical Details

White Light LEDs are Problematic for Human Circadian Systems

Human circadian sensitivity to wavelengths compared to wavelengths of white-light LEDs

Human photopic and circadian sensitivity curves displayed against a typical blue-rich LED light source spectrum.

I am normally first in line to argue and work for improved energy efficiencies. However, efficient pollution is still pollution. The new white-light LEDs that are grabbing an ever-increasing market share of the lighting business are a prime example: Because their blue light output component is so strong, and because our atmosphere most efficiently scatters blue light (called Rayleigh scattering hence the reason the sky is blue), the increasing use of LEDs for exterior lights would increase the amount of blue light about at night and so increase the problems that blue light causes for humans and animals.

LEDs have been around for some time now. So if energy efficiency was the only thing driving this change, then low-pressure sodium lights would have been replaced by yellow LEDs some time ago. But because of our preference to see the world in only daytime lighting levels and full daytime color, we seem to be rushing to embrace something that is not entirely the best for us. The International Dark-Sky Association has put out a white paper about these new lights and their analysis of them. The graph above demonstrates how well the new blue-rich LED lights would interfere with our circadian system and our ability to get a good night’s sleep.

Thus, care should be taken ensure that we are not harmed by our rush to progress. To help people make better lighting choices, to improve all of our sleep, the environment, and any viewing conditions of the heavens, just remember this simple thought about your night-time light:

BLUE BE BAD.

See What’s Lit, Not the Light.

You can light the same place more safely and more effectively by making a lighting plan beforehand. Compare these two parking lots:

Two parking lots with different glare lighting results.
Image Credits: International Dark-Sky Association

The parking lot on the left exemplifies shielded lighting. Note how few lights are needed to illuminate the area and how it is done without glare.

Next, the photo on the right shows lights shining into the sky and creating painful glare. Just what is the business owner trying to achieve with this overly-lit lot — blinded customers?? There are so many poorly aimed lights being used that they almost seem to be trying to out-compete each other rather than illuminate the lot.

Which lot do you think people will feel is more comfortable, more welcoming, and less oppressive to drive into?


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