Short Wave - LED Lights Make You Sick? We Found Out What Causes It

Episode Date: December 22, 2023

LED light bulbs are the future. They're better for the environment and the pocket book. But for some people, certain LEDs lights — particularly holiday lights—are also a problem. They flicker in a way that causes headaches, nausea and other discomfort. Today, we visit the "Flicker Queen" to learn why LEDs flicker — and what you can do about it.Wondering about other quirks of lighting and engineering? Email us at [e-mail] – we might cover it on a future episode! See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. Since I was a kid, one of my favorite things to do this time of year is to stroll around neighborhoods looking at all the holiday lights. They're just so romantic and full of irrepressible twinkling cheer. But then something happened around a decade ago that made that twinkling a little less cheerful, at least for me. I can still remember it clearly. the first time I found myself staring at Christmas lights with LED light bulbs.

There was just something about the light that made my head spin. Like the whole world was jittery and off. Turns out it's a phenomenon called Flickr, and I wanted to understand how it works, so I went to meet the Flickr Queen. You know, I'd rather be known as the Flickr Goddess. But I didn't name myself, so I'm stuck with Flickr Queen. Naomi Miller is a lighting scientist and designer at the Pacific Northwest National Laboratory.

She's been studying LEDs for nearly 20 years, and she says flicker is a real problem for some people. It may cause headaches or migraines. Other people report nausea. And we do know that people who have had traumatic brain injury in the past seem to be more susceptible to problems from flickering LEDs. It's unclear just how many people. people are bothered by Flickr. But this is potentially a big problem because LED lights are the future. The U.S. government has been working for more than a decade to require that light bulbs become more and more efficient. And it culminated in a regulation earlier this year that in effect

banned the sale of most incandescent light bulbs because they are hugely inefficient. This transition to LEDs is a big win for the environment. They use about a fifth of the energy that incandescent used to use? The Department of Energy predicts LED lights will cut carbon emissions by more than 200 million metric tons over the next 30 years. Not to mention help people save nearly $3 billion per year on their utility bills. Plus, they just last a very, very long time. Instead of replacing them every two years, for example, you may replace them every 10 years, or you may will them to your children. I don't know. And to be clear, LED technology has come a very long ways,

and many LED lights have solved the flicker problem. But if you're like me, and you've ever noticed those bright car tail lights that leave tracers across your vision, or those holiday lights that twinkle all wrong, then today's show is for you. We're heading to the Pacific Northwest National Laboratory to learn how LED lights work, and why some of them drive some of us up the way.

wall. I'm Aaron Scott, and you're listening to Shortwave, the science podcast from NPR. This is where the magic happens? Pretty much. When I show up in the lab, Naomi has set out three strands of white holiday lights on a table in a dark room. And in front of each is a sheet of paper with a graph showing the wavelength of its light. Can you kind of take us through these and why you chose these particular lights? Well, every year I go to the big box stores and I look for holiday light strings that don't flicker. And every year I'm disappointed.

So sometimes I go and I say, oh, my goodness, there's one that doesn't flicker. And then I'll look closely and it's still incandescent. So the one you see on the right, this is an incandescent holiday light string, still available, maybe not available next year. Beautiful, smooth, light output. It oscillates in light output about 120 times per second, but it doesn't go from full on to full off. It goes from full on to maybe 85% of on

and then back up to full and then down to 85%. But it varies in a sinusoidal pattern. A pattern that on her graph looks like a wave. And evidently our eye brain system accommodates that pretty, well. And I look at it, I mean, it's a warm kind of golden glow. Yeah. Well, I'm kind of a sucker for old incandescent holiday lights myself. But it was probably 20 years ago that we saw the introduction of LED products. That brings us to the middle string of lights. At first glance, it looks the same as the incandescent string. Both are white cords with small white lights. But these LED lights, but these LED

lights would make Rudolph crash. So you can see in the little pattern that I've drawn here, that it's on for a little bit of time and then it's off. And it's the fact that it's going from full on to full off for a chunk of time that makes you see it as flicker. It drives me nuts. I look at it and it looks like they're kind of vibrating or shimmering. And like that almost kind of makes it feel like the whole world is like just shaking a little bit. Exactly. Now, this one's an especially bad one. This one operates at 60 hertz, which means it's going on and off 60 times a second.

To understand why LEDs are turning fully on and off over and over, as opposed to incandescent light bulbs, which ebb and flow from full on to mostly on in a way that we don't see, we need a little LED 101. LED stands for light emitting diode. The LED is mostly a silicon chip that when it receives current, it gives off light. And when the current is no longer delivered to the LED, it stops giving off light. So it's a very direct light source dependent on the electronics that is driving the LED. In LEDs, the electronics are everything.

determine how often the LED turns on and off and the shape of its waveform. One way to control LEDs, and especially to dim LEDs, is to turn it on and off rapidly, which according to your eye, your eye integrates over time, and you may turn that LED on, 50% of the time, off 50% of the time repeatedly. And your eye will see that as being dimmed down to 50%. However, some people may see that on-off operation as being distracting or disturbing. And so only certain people's eyes register that, though, or is it only that it bothers certain people? It may be a combination of both. We don't really have all the human factors explanations yet. But we know that this doesn't occur for most LED products, because most LED products have better quality electronics.

built into them that maintain the light output over time. And those products people don't object to. And that brings us to the third and final string of lights on the left. This one is a green cord with those larger egg-shaped bulbs. Notice how it says flicker-free bulbs. Okay, so companies are trying to make it a selling point. Right, but it's a lie. Oh, no. Because they flicker. I don't know what standard they have for flicker-free, but it doesn't work. They are better than the middle lights, because according to Naomi's graph, they're actually turning fully on and off twice as fast, 120 times per second instead of 60 times. If I look straight at them, I don't notice the flicker that much.

But if they're on the edge of my vision, it's unmissable. So the 120 hertz frequency is generally a little better tolerated, but it still drives some people bananas. it may still drive you bananas. It certainly is distracting for me. Yeah, I'm not registering it the same way. I'm with this other set of LED lights where I look at it and it, yeah, it just kind of makes me question existence a little bit. It's all jittery.

And I can explain that. That's what we call low frequency flicker. It happens when lighting modulates or changes between 3 and 80 times per second or 3 and 80 hertz. So low frequency is the stuff. that we don't see very often, and it would make me really nervous if it did, because there is a possibility that people who are affected by epilepsy, photosensitive epilepsy, may actually have a poor reaction. So we really want to avoid this low frequency stuff. But higher frequency LEDs, like the supposedly flicker-free holiday lights on the table,

they can still flicker two in two different ways. The first is known as the strob. It turns out that the stroboscopic effect is when you are, generally you have a fixed gaze and something's moving in your field of view. So as an example, I'm going to look at this holiday light string and I will move my finger, wave my finger in front of it, and you can probably see a pattern from my finger. It's eerie. I mean, it's like when a strobe light is going where you're registering kind of, multiple fingers so that even though I know your fingers moving, I'm seeing these tracers that are kind of staccato scattered behind it. That's right. So that's a way to identify stroboscopic effect when you have a moving object in the light. Another way to identify it is to film the lights in your phone slow-mo setting and then watch the video. The strobe effect becomes really, really noticeable. We have a link to a video I filmed in our show notes showing Naomi waving a wand to show the

stroboscopic effect, and then the slow-mo cranks up showing the actual strobing. Check it out. It's intense. Finally, another form of flicker is one some people notice driving at night when they're looking at bright LED car lights. And suddenly, as your eye moves around the roadway normally, you will see a repeating pattern of lights. So you don't see one tail light anymore. You see a whole string of taillights spaced at some distance apart. This is called the Phantom Array Effect. And Naomi says some folks find it unnerving because it makes it hard to see where the actual light on the moving car is.

I'm curious what you all here at the Pacific Northwest National Laboratory are doing to work with manufacturers to try to solve this problem. Well, one of the things we're doing is working through the Illuminating Engineering Society. that's a group of lighting geeks and we're writing a document which ultimately we hope will become a standard to tell manufacturers this is what is a good waveform

this is a bad waveform and here are things you can do with your combination electronics and LEDs in order to make a system that won't cause potential health issues for some people. We're trying to work within the current marketplace and make LEDs better and make LEDs more widely adopted because they save so much energy. Do you have any advice for people who are bothered by Flickr beyond literally just going out and buying a span of products, bringing

them home, plugging them in? I mean, is that really kind of the best we can do at this point? There are websites popping up that look at Flickr from from common light bulbs that you can buy at the store. There are also, for example, websites that evaluate different cell phones because cell phones, some cell phone screens, can exhibit flicker. But I will tell you, if you're buying light bulbs, don't buy the cheapest stuff. Generally that helps. And be prepared for the fact that you may have to change out your dimmer because not all old dimmers work politely with the new LED technologies and look for low flicker use the tricks of waving your finger in the light to see if you see multiple fingers

and you know what i suggest you take the light bulbs back to the store if you don't like them because the manufacturers need to know that people are unhappy with these products i still think it's going to be a subset of products. Even so, take them back. Excellent. Thank you so much, Naomi, for talking with us. My pleasure. I'm so glad you're interested in Flickr. Sometimes we think we're the only goofy people in the world. This episode was produced by Burley McCoy and edited by our showrunner Rebecca Ramirez. Britt Hansen checked the facts. The audio engineer was Josh Newell. I'm Aaron Scott. Thanks for listening to Shortwave from NPR.