What’s So Bad About Blue Light?

Many white light sources contain a significant amount of blue light. Image: Evan Smogor

Too long; didn’t read

• Most LED lights are not dangerous to normal, healthy eyes*.
• LEDs can negatively impact your sleep and daytime energy if used inappropriately.
• But you can use blue light to your advantage. It’s all about timing.

I promise this article will be really fun and informative if you actually read it.

Fluorescent Incandescent

Yeah, I just threw dance music into a serious article. Light emitting diodes aren’t going to have such a catchy track written about them any time soon.

I digress. Incandescent and fluorescent are old news. You can’t even buy most incandescents anymore.

Incandescents have had an incredible run, but, regrettably, there’s no room for such energy-sucking lamps in the modern world.

—Los Angeles Times

Sayonara, energy suckers. We’re here to talk LED.

Blue (Da Ba Dee)

Why is everyone freaking out about blue LEDs? That LED bulb I just got is white, not blue. Just like an old energy sucker.

Here’s why: those light bulb factories in China are employing magic to make that thing look white. Underneath, it’s all blue.

I’ll make it easy for a mere muggle to understand. The thing that initially lights up in an LED is blue and blue only. We’ll call it a blue pump.

It’s so blue, it hurts to look at. Not even joking. You shouldn’t try it.

On top of the blue pump, those LED factory wizards apply this yellow thing. It’s called a phosphor.

The phosphor takes the light from the blue pump and spreads it out into white light. Kind of like a prism, but in reverse. Kind of not really.

Phosphor color conversion actually involves photons, which are pretty mystical. I haven’t thought of a good analogy for this process yet. You can research how it works on your own.

Let’s keep this on the topic of blue light.

Remember from science class, all the colors of light add up to white? Including blue.

The phosphor doesn’t get rid of blue light. It’s still there in the white light output.

But as long as you’re not staring directly at the light, most LED lights are not dangerous to normal, healthy eyes*. LEDs are no more hazardous than other light sources, including incandescent.

Just don’t stare at lights. And use shades when lights are too bright.

All of the Lights

So if most LEDs are not dangerous to most healthy people, what’s the big deal?

You see, these new-fangled lights are everywhere, all the time.

In Paleolithic times, day was day and night was night. Nighttime illumination came from only two sources: fire and moonlight.

Our bodies evolved a sensing mechanism just to detect when it was daylight and when it was not. Like it or not, we still have those daylight sensors in our eyes and they still work.

Those eye sensors are only triggered when there is blue light. Let’s lay the inputs out clearly:

• Daylight: Lots of bright, blue light
• Moonlight: Dim light with some, but much less, blue
• Firelight: Dim to bright light, but little to no blue
• Modern artificial lights and electronic screens: Dim to bright light with significant blue

When there is significant blue light, the sensors send a message to the body clock that it is daytime.

The body clock regulates when we feel tired and when we feel awake. And it plays a major role in many other important body processes.

I’m no luddite, and I wouldn’t want to return to any earlier time than right now. I think people should use technology more, not less.

But we must realize that all these lights and displays are telling our bodies that it is daytime all the time.

It’s like perpetual jet lag. Or working a different shift every day. And it’s suboptimal for our health.

Slave to the Rhythm

What are we supposed to do, then?

It turns out we can use blue light to our advantage.

Remember, the body block tells us when to be awake and when to feel sleepy. It’s critical for a number of other functions crucial to our health. Everybody has one.

Another name for the body clock? The circadian rhythm.

Rhythm. Can you sense a theme here?

The circadian rhythm works best when it gets a lot of blue light in the early-to-mid part of the day. It also works best when there is little or no blue light at night.

What are sources of significant blue light?

• Old-fashioned daylight
• Bright LED lighting
• Cool white LED and fluorescent lighting
• Electronic displays without color filters

And what are some ways to minimize blue light?

• Dimming or turning off lights
• Using night lights or accent lights instead of the regular lights
• Color filter apps like f.lux and Night Shift
• Blue-light blocking glasses
• Blackout window shades
• Sleep masks

Use the sources of significant blue light earlier in the day. Transition toward the methods of reducing blue light in the evening.

It’s that simple.

You’ll feel better, and your circadian rhythm will thank you.

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*If you have an ocular medical condition, you may need to take additional precautions around light. This statement applies to all light sources, natural and artificial. Consult your doctor. I am not a doctor and don’t play one on the internet.