Public Health Risks

Flickering LED lights and screens create significant public health risks - schools and other public locations are highlighted below. Sensitivity to toxic lighting is not a disability and should not be "accommodated" by exclusion. This kind of lighting didn't exist throughout almost the entirety of human evolution, so resistance to toxic lighting may be a lucky accident for some people, rather than an expected ability.. A significant fraction of the population may be adversely affected by flickering light and resistance to adverse health effects may be temporary for some people. The lighting is the problem, rather than those of us who are sensitive having the problem - we do not necessarily have undiagnosed medical problems that need to be fixed and it is unreasonable for lighting and screen companies to tell us to fix ourselves rather than producing safe products. Flickering light is dangerous to all sensitive people, most of whom might not realize that the light is causing their health problems. The most vulnerable people, including children, may not even be able to express what's happening to them. 

Perhaps the best study of the affect of flickering light on the rate of headache and eye strain in people was that of Wilkins et al. who did a double-blind study of office workers where they shifted highly flickering magnetic ballast fluorescent lights with low flicker electronic ballast (modern) fluorescent lights without telling the workers partway through the study. One of the most significant take-aways from that study was that the workers were totally unaware of when the lights had been changed, despite marked differences in rates of headaches and eye strain under the different lights. This supports the idea that most people will be unaware of the effect of lights on their health. I know that I was unaware lights causing early symptoms until my symptoms became so debilitating and flickering lights so painful that the effect of the lights was all too obvious.

The page below shows images of flickering lights and screens - see the Testing LEDs and Screens page for a more thorough explanation of how to capture and interpret such photos and for more context for how the health impacts of the lights below compare to how other LED lights and screens have affected my health. Briefly,

(1/2 cycle per frame) x (240 frames per second) = 120 cycles per second = 120 Hz

Wilkins et al. Fluorescent lighting, headaches and eyestrain. Lighting Research and Technology, 21, 11-18 (1989).

Dangerous Flickering Lights Installed in NYC Public Schools

The image below shows 4 consecutive frames from a slow-motion smart phone video filmed at 240 fps of the LED lights that were installed the night prior to February 16th, 2022 on the second floor of the New York City Public School building that was my primary worksite. The old fluorescent T8 tubes were taken out of the fixtures and replaced with LED T8 tubes. 

This pattern is typical of 120 Hz flicker, with a full cycle taking 2 frames, although the contrast between bright and dim varies for different lights with 120 Hz flicker. More subtle flicker may be difficult to notice when consecutive frames are placed side-by-side. The flicker for the light below is obviously visible if the slow motion video is played at the typical playback speed of 30 fps. I find the flicker when such videos are played to be quite painful and triggering of symptoms, so I have chosen to show consecutive frames, rather than the actual video, since the difference in brightness in consecutive frames is visible enough in this format.

This is a closer view of a section of the same 4 consecutive frames from a slow-motion smart phone video filmed at 240 fps of the LED lights that were installed the night prior to February 16th, 2022 on the second floor of the New York City Public School building that was my primary worksite. The old fluorescent T8 tubes were taken out of the fixtures and replaced with LED T8 tubes. The LED T8 tubes have 120 Hz flicker. It's imprecise to estimate percent flicker from such a video, but based on prior experience I'd estimate that it's somewhere between 20% and 100%, with my best guess for its probably being closer to 100%.

While the flicker in the above consecutive still images may appear somewhat subtle, it is much more obvious in the original video:

New LED lights on the second floor of an NYC Public School Building on 2/16/22, slow-motion video at 240 fps. WARNING: View with caution if sensitive to flashing lights.

Old fluorescent lights on the first floor of the same NYC Public School Building on 2/16/22, slow-motion video at 240 fps.  These fluorescent lights had also been replaced with flickering LEDs by the following day. The graph below shows the flicker of classroom fluorescent lights in the same NYC public school which are probably similar to the removed hallway fluorescent lights.

These flickering LED lights were immediately painful, causing a sharp pain behind my right eye, when I came onto the floor and traversed the hall for less than a minute while entering the room where my organization is based. I immediately went to the facilities office to alert them to the problem and sent an email cautioning about the potential danger not only to me, but also to the health of school children and their ability to learn. My email was forwarded to the higher-level facilities administrators elsewhere in the NYC Department of Education who were in charge of the light replacements. The next day, the lights on the first floor had also been replaced with the same LEDs, preventing me from safely reaching our classroom. I had brought a blindfold and had other people lead me into the building so I could collect materials to bring home. I have not been able to safely return to this school building since then. From my brief exposures to the flickering lights on 2/16/22, I developed a headache with pain and pressure in my right temple and a feeling of swelling in my right temple that was strong the next few days and lingered in a minor, slowly tapering way for weeks. I also had insomnia (early morning awakenings) in the 2 weeks following this, with sleeping extra hours for a few more weeks. Extra fatigue lingered for longer. After speaking with OSHA and then PESH, who said they couldn't do anything about children being at risk, I also called and emailed the New York State Department of Education to alert them to the danger to the health and learning of school children on 3/22/22. They said it's an NYC issue, not a state issue. I also contacted the FDA and EPA to try to figure out how to appropriately report health problems from LED lights. Initially, I was told by representatives of both organizations that I can't report health problems with LED lights either to the FDA or EPA because there are not yet federal regulations for LED lights that could have been violated. OSHA and PESH said they couldn't help with workplace safety issues if there weren't regulations being violated. They could only assist to help me get accommodations, which I didn't need because my current employer is already very accommodating. They said they couldn't do anything about the NYC Department of Education creating an unsafe workplace for me (and by extension and unsafe learning environment for children) since I am not an employee of the NYC Department of Education but just work in one of their buildings. Attempts to report the issue to the NYC Dept. of Health and Mental Hygiene also failed, although a representative suggested contacting the NYC Commission on Human Rights, which never responded to me. In August of 2022, a report to the FDA made it to the correct office which said mine was the very first report of health issues they had received about LED lights and they indicated the correct way to report health issues with LED lights.

I am extremely concerned about the potential impact of flickering lights in schools on the health and ability to learn of children. While the flicker of the above lights being installed in NYC public schools is extreme, days of exposure to fairly low flicker at the school where I taught from 2008-2019 (LED lights with 0.7%, ~1000 Hz flicker installed in the fall of 2018) was sufficient to trigger all of my most debilitating symptoms. If I had been forced to attend a school with such lights when I was a child, I would have had constant headaches and severe pressure in my head, loss of any ability to use short-term memory, constant spatial disorientation, nausea, severe sleep problems, and tortuous pain when in the flickering lights. I would have been unable to read for comprehension or add numbers due to the loss of working memory. Perhaps I would have been misdiagnosed with anxiety or ADHD or a learning disability. I would have had no hope of being repeatedly recognized for my scholarship and attaining a PhD. It's hard to know what kind of career might be open to a child like me if the lighting and screen situation stays the same as it is now. I couldn't expect to do any job that requires screen use or do any job requiring work under LED lights or work in the presence of automobile LED lights. In NYC, even a job in the parks would be out of reach, as the new flickering LED lamp lights are often left on in the daytime.

While I hope that few children are as severely affected by flickering lights as me, it is quite likely, given earlier research on the effects of the flicker of old magnetic ballast fluorescent lights (for example, Wilkins et al.), that a significant fraction of the general population may experience headaches or eyestrain due to LED flicker too, which of course also are significant health and learning concerns. Additionally, reports from sensitive individuals on and in the LED Sensitivity Survey indicate that LED lights and screens can trigger additional serious symptoms in some people than what I experience, including debilitating eyestrain, anxiety and depression.

There is evidence that student test scores have been falling since 2012 and poor performance is correlated with screen time (evidence in the PISA report and elsewhere discussed by PISA director Schleicher and reviewed by Thompson in The Atlantic). As an educator, I have witnessed the danger of screens being distracting and leading to adverse social interactions and social anxiety that is described in this article. However, I also think LED and screen flicker could very likely be interfering with student learning through (1) impaired ability to concentrate when in light/screens flicker (through impairment of vision/tracking), (2) physiological impairment of health/brain function caused by flicker, and (3) anxiety/depression triggered through physiological changes in the brain triggered by flicker.

Since there is not yet a test to screen children for LED sensitivity and children should be able to receive an education in a safe environment, I beg the lighting industry to start to make completely flicker-free LED lights appropriate for schools and other public places. The technology to do so already exists (see LED lights). I also beg computer hardware and software manufacturers to work with the LED sensitive community to figure out how to produce screens and software for controlling the images on those screens that are safe. In the meantime, screen use is a risk for children - and modern screen and image rendering technology seems to often be more triggering of health problems for sensitive people than earlier technology (many posts on and my own experience), so the risk now is much greater than in the past. The risk is also greater now because the flicker of ambient LED lights tends to exacerbate screen sensitivity (many posts on and my own experience).

Schleicher, Andreas. PISA 2022: Insights and Interpretations. OECD Programme for International Student Assessment.

Thompson, Derek. It Sure Looks Like Phones Are Making Students Dumber: Test scores have been falling for years—even before the pandemic.The Atlantic, December 19, 2023.

Wilkins et al. Fluorescent lighting, headaches and eyestrain. Lighting Research and Technology, 21, 11-18 (1989).

Dangerous Flickering Lights and Screens Installed in NYC Subway Stations, Subway Trains, and at Bus Stops

Recently, the Metropolitan Transportation Authority (MTA) has been updating public transportation in NYC by replacing fluorescent lights in subway stations with flickering LED lights, installing flickering LED screen signage and advertisements on subway trains, in subway stations, and at bus stops. This includes replacement of print advertisements on subway trains with flickering LED screens that are at eye-level for standing passengers and run the length of the train car. These screens have severely flickering backlights and are very triggering of symptoms for me. I have heard from acquaintances who get headaches from flickering LED lights that these eye-level screens are intolerable for them too.

The image below shows 4 consecutive frames from a slow-motion smart phone video filmed at 240 fps of the LED lights on the express platform at the Lexington Avenue 4/5/6 Subway Station in NYC. The entire frame is shown for each image. 

The image below shows 4 consecutive frames from a slow-motion smart phone video filmed at 240 fps of the LED lights in the 4/5 area of the Borough Hall Subway Station in NYC. The entire frame is shown for each image (people's faces covered with the black rectangle). Notice how the light alternates between greenish and reddish in consecutive frames.

In the past, the lights in both of the above stations had been fluorescent and hadn't bothered me. I used these stations for the first time since Covid on June 3rd, 2022 and filmed 3-second slo-mo videos at each station. As soon as I entered the 86th St. station, I could tell that the lights had been changed- they were a little painful and they had the quality that I associate with very flickering light. Additionally, I knew that high flicker from this kind of tube light typically can trigger symptoms for me within seconds. I got to the platform as quickly as possible and immediately put on a blackout mask, briefly taking the video while wearing welding glasses. I switched briefly from blackout mask to welding glasses to enter the train. I decided to keep the blackout mask on throughout the train ride so I'd be able to know that any symptoms were due to the station lights - typically it takes 45 min to an hour for pressure to build up in my head along with the onset of long-term symptoms following a flicker exposure, so I'd have to wait and see. I switched to welding glasses when I got off at the Borough Hall station, pausing to take the video as I otherwise hurried out since these lights also seemed to be new and flickering. Once I got to my destination (a glass space illuminated by sunlight), pressure was starting to build in my head - about 45 minutes after I had been in the 86th St. station. The head pressure increased and I had significant pressure and pain in my right temple lasting 8 hours. Although I felt better the next morning, such symptoms from just a few seconds of exposure, make it impossible to use subway stations with flickering LED lights and still work.

Prior to this, I had been able to use the subway. The old stations all had fluorescent lights, which were completely tolerable. While the overhead LED lights in the new Second Avenue Subway Stations have a little flicker and I need to protect my eyes during extended waits, they're not so triggering that I can't navigate to the platform - with welding glasses when I'm most sensitive. The most triggering aspect of these new stations are the flickering LED screens on the platforms. These had initially been inactive, but became active at some point during Covid, making these stations much less accessible than they used to be. 

With the switch from fluorescent lights to LEDs with extreme flicker in the old subway stations, I now essentially can't take the subway. The flickering advertisements and the flicker of LED lights on buses also make buses inaccessible. A report of the safety issue sent to the MTA resulted in them telling me that my only option was to apply for Access-A-Ride service - a notoriously unreliable van service designed for people with disabilities. Since I am not disabled, this doesn't seem to me to be appropriate. 

This image below shows 5 consecutive frames from a slow-motion smart phone video filmed at 240 fps of a new LED screen at an NYC bus stop. The video was filmed in portrait orientation, but the bottom part of each image is cropped out here. Notice the black bar in the middle of the screen in frames 1 and 4 and at the sides of the screen in frames 2, 3, and 5. Such banding indicates that the screen is flashing on and off at a faster rate than 120 times a second. The phone scans from left to right (or the opposite) when capturing one frame of a slow-motion video, so a dark band indicates that the screen was off during the period in which that portion of the frame was photographed. Although, it's not possible to accurately determine the flicker rate from such a video, my best estimate is that it's around 500-1000 Hz. 

On a different night after dark, I recorded the flicker waveform for this screen shown below, showing 100% 120 Hz flicker with a long off period between "on" pulses. It's possible that the flicker rate is different during the daytime compared to after dark to achieve different dimming. 

I find this kind of screen to be painful to look at even from blocks away (if viewing the street from an upper story of a building). These bus stop advertisements are one of the main factors limiting the accessibility of NYC sidewalks, even on sunny days.

While the flicker in the above consecutive still images may appear somewhat subtle, it is much more obvious in the original videos, available here:

Flickering LED Lights at NYC Subway Stations and a Flickering LED Screen at an NYC Bus Stop. WARNING: View with caution if sensitive to flashing lights.

This images on the right below show 6 consecutive frames of a section of a slow-motion smart phone video filmed at 240 fps of the main hall at Grand Central Terminal. The photo on the left shows an entire frame. When visited in midafternoon in February 2022, despite the sunlight, the flickering lights caused pain immediate pain in my right temple and I went back outside to avoid further symptom development

While the flicker in the above consecutive still images may appear somewhat subtle, it is much more obvious in the original videos, available here:

Flickering LED lights in Grand Central Terminal. WARNING: View with caution if sensitive to flashing lights.

Dangerous Flickering Lights Installed in Medical Offices and Hospitals

Due to the installation of flickering LED lights in their offices, I am no longer able to safely visit the doctor. Flickering LED lights at my neuroopthalmologist's office triggered severe long-lasting symptoms for me, including a peripheral blindness during a visual field test during that visit. My PCP has flickering LED lights in the office and I'm unaware of other local offices that haven't yet installed flickering LEDs. A visit to a medical imaging office that I had used for years led to an episode of symptoms  - they had installed flickering LEDs. I got significant symptoms even though I tried keeping my blackout mask on most of the time, wore welding glasses when I needed to walk somewhere, and carried the forms outside to the sunlight to complete.

I now have to bring my own flicker-free lights with me to the office and have someone lead me in blindfolded. The necessity to arrange a time that office staff can bring me blindfolded into the building makes scheduling extremely difficult - a six month delay most recently before I could have a yearly physical. This is a significant barrier to care if I get sick. I couldn't go to the hospital without wearing a blackout mask and It's problematic that all of the blackout masks I've tried so far don't work that well and need to be mostly held in place. This could make a safe hospital stay impossible.

I am not the only one being denied safe healthcare due to flickering LED lights.

The image below shows the flicker waveform of the waiting room LED lights in the neuroophthalmologis's office where the lights caused peripheral blindness. Note that the 1% flicker of these lights seems quite low. These and other LEDs that trigger concussion-like symptoms for me can have flicker that is lower than that of incandescent lights. There is something different about the flicker of LEDs compared to incandescents besides the basic waveform. I explore these possible differences, including color flicker and color spectrum, further in the detailed analysis of flicker data posted in the fall of 2023.

Dangerous Flickering Lights Installed in Grocery Stores

The image below shows 4 consecutive frames from a slow-motion smart phone video filmed at 240 fps of the LED lights that were installed on June 9, 2021 in my local NYC grocery store; the entire frame is shown for each image. The lights were immediately painful and a 5 minute trip into the store while wearing a hat and welding glasses triggered symptoms lasting several hours. Prior to this installation, this grocery used fluorescent lights that didn't bother me and I didn't wear a hat or tinted glasses when in the store. I haven't returned to this grocery and haven't yet found a local alternative grocery without flickering LEDs. Sending reports and requests to safe lighting to Fairway Market, Whole Foods, and additional local markets as well as the NYC Dept. of Health have not resulted in any action. 

While the flicker in the above consecutive still images may appear somewhat subtle, it is much more obvious in the original video, available here:

Flickering LED lights at an NYC Grocery: WARNING: View with caution if sensitive to flashing lights.

One of the last groceries in the neighborhood to change from fluorescent to LED lights was Morton Williams. The graph on the right shows the 55%, 120 Hz flicker of their new LED lights. After entering after the switch to LEDs, I immediately took a meter reading, and based on that immediately left the store.  The less than 60 seconds in the store while wearing a hat and welding glasses resulted in concussion-like symptoms lasting about 24 hours. The head pain and pressure started to build up about 5 minutes after leaving the grocery. There are no groceries without flickering LED lights in my neighborhood now.

I currently don't have a way to access a grocery without some amount of LED flicker exposure, either from store lights, screen flicker, or the flicker of lights on public transportation. Only the outdoor Saturday farmer's market and fruit carts are free of flickering light.

People should not be forced to choose between food and avoiding brain injury.

Holiday LED lights with 60 Hz flicker seem to be especially dangerous

Traditional incandescent holiday lights have 120 Hz flicker, but even now that I am extremely sensitive to flicker, I can mostly tolerate them. In December 2023 I spent several days in a home decorated inside with dozens of strings of incandescent holiday white "fairy lights" with 14.5% sine wave flicker. I could mostly tolerate these lights, especially during the day when mixed with sunlight. At night they became very slightly painful and they might have had a slight impact along with a few LED lights visible through windows in causing very minor symptoms for me. In contrast, LED holiday lights can trigger severe symptoms for me in seconds to minutes.

While household LED lights typically have 120 Hz flicker and all incandescent lights have 120 Hz flicker, many holiday LED light strings are now being engineered to have 60 Hz flicker. This makes their flicker more visible and can create an extended "off" period. For example, the white LED lights shown below are off ~75% of the time and have 60 Hz flicker. This makes their flicker especially severe.

Notice also that the white 60 Hz lights below and the blue 60 Hz lights are on at opposite times (frames 2,6 and 10 for white vs frames 4, 8 and 12 for blue) . I don't know whether they are engineered differently - one on when electrons flow in and the other on when electrons flow out of the circuit - or if the timing of the flicker depends on which way a non-polarized plug is inserted in an outlet. The latter possibility could mean that different light strings within a room could theoretically be flickering in opposite phases, which might be particularly injurious and possibly increase the risk for triggering seizures, especially if their colors differ.

The holiday lights below triggered days of symptoms, including brain fog, head pressure and insomnia for me. In late December 2022 I was seated in a family member's kitchen where I visit often, when, after a few minutes, sharp pain behind my eye typical of ongoing flicker injury started.This was very unusual - I was typically safe enough there. We tried unplugging the incandescent Christmas tree lights behind me, but that didn't help. We turned off the overhead incandescent lights, but that made the sharp pain worse. Then I took a slo-mo video to try to find the flicker source, including of lights visible through the kitchen window in neighboring apartments. Upon noticing alternating blue/white 60 Hz flicker in one window, we lowered the curtain in the kitchen and that eliminated the sharp pain behind my eye. Head pressure and other symptoms continued to increase in intensity, as is typical for me following a flicker injury. These 60 Hz holiday lights were much worse than typical 120 Hz non-holiday lights in terms of how quickly they triggered fairly severe symptoms. 

NPR Short Wave reported a warning of of some of the potential health risks of LED lights on December 22, 2023. Naomi Miller of Pacific Northwest National Laboratory highlights the increased flicker visibility and possible health risk of 60 Hz LED holiday lights.

Scott, A., McCoy, B. Ramirez, R. It's not just you: Christmas lights look different now, and can give you headaches. December 22, 2023. National Public Radio: Short Wave.