Despite claims by some websites to the contrary, LED bulbs don’t put out inordinate amounts of blue light.

Leland Teschler, Executive Editor
Take a look at some of the websites devoted to alternative medicine and you’ll likely come across headlines like, “The Dangers of LED & Blue Lights Will Blow Your Mind!” or, “LEDs: The Blue Light Risk,” or “Artificial lighting and the blue light hazard.”

These all stem from the belief that light in the blue part of the spectrum causes medical problems, everything from insomnia to promoting macular degeneration. And LEDs are supposedly a major source of blue light. Here’s what one of the websites cited above says on the subject: …..the most efficient LED bulbs of the day are almost exclusively emitters of predominantly blue light, though there are some exceptional products that mix all colors of the spectrum—but not many are available or affordable for house use.

Scary. And wrong, at least as far as we can determine. These pronouncements come from a website that aligns itself with the herbalism. We tend to be skeptical of the alternative medicine crowd. So when we came across passages such as the one quoted above, we decided to run our own tests of LEDs.

It’s not difficult to check claims about the wavelengths of LED output. To do so, we obtained a light meter designed for use by architects and room-lighting specialists who need to set light levels. To this we added an optical bandpass filter which only passes light in the blue-wavelength range, about 450 to 490 nm.

Our light meter was an LT45 made by Extech. It’s normally used for measuring and optimizing environmental light levels in places like office buildings, manufacturing plants and schools. Light meters like this one are used to verify regulatory compliance with local public safety codes and OSHA workplace lighting dictates.

Our blue bandpass filter (BP470-30.5) came form Midwest Optical Systems Inc. Its spectral range is 425 to 495 nm with a ± 10 nm tolerance.

To decide what LED bulbs to check, we went to Consumer Reports. As with other product categories, they rank LED bulbs. So for samples, we used five 60-W-equivalent LED bulbs that Consumer Reports puts at the top of its rankings. They included bulbs from Sylvania, Philips, EcoSmart, and by Feit. We also got hold of two incandescent 60-W bulbs, one with frosted glass, the other without.

For testing, we put each bulb in a completely dark room and measured its illuminance using the light meter. The light meter sat one-foot away for measurements with and without the blue band-pass filter. These measurements let us calculate the percentage of blue light in output from each of the bulbs.

We’ll cut to the chase. All of the 60-W equivalent LED bulbs we measured had less than 2% of their output in the blue light range. The average blue light output for the bulbs we tested was 1.4%. That’s a long way from being “emitters of predominantly blue light.” Moreover, both incandescent lights also had under 2% of their output in the blue wavelength range. And lest you think we tested super-pricey bulbs that few people can afford, one of our Sylvania bulbs cost a little over a dollar on Amazon.

To give the alternative medicine crowd the benefit of the doubt, we also tested an old LED bulb that came out before the DoE held its “L Prize” event in 2011. The L Prize is credited with kicking LED bulb development into high gear. So, we reasoned, perhaps bulbs made before then had the problematic blue light output. But the results were the same. We had one pre-2011 LED bulb on hand for testing (from EcoSmart). This dimmer bulb, too, emitted less than 2% of its output in the blue wavelengths.

We aren’t done testing. The five bulbs at the top of the Consumer Reports list all put out relatively warm light. There are others whose light is colder, in the 3100 to 4500 K range. Eventually we’ll check a few of those as well. But so far, it looks as though you’re no worse off lighting your rooms with LEDs than with ordinary incandescent bulbs.

It’s best to take all those scary scenarios painted by alternative medicine websites with a grain of salt.