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THE LIGHT DOCTOR 5: You Have the Right to Healthy Light.
Chapter 5 shows there are no valid excuses for delaying the transition to healthy circadian lights.
Take a walk down the lighting aisles of your local hardware store and you will find an overwhelming diversity of lamps and fixtures. But almost all light bulbs that you can buy today for your home are blue-chip LED products. Gone are the incandescent, halogen and fluorescent lights of the past. We have entered the era of the blue pump LED.
It is the same story when you peruse the catalogs and websites of the commercial lighting manufacturers who supply offices, schools, hospitals, senior living, retail and everywhere else. The blue-chip LED reigns supreme.
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Despite more than 20 years of scientific evidence showing that blue-rich light in the evening disrupts our circadian clocks, our sleep and our health, we have created a world where virtually the only illumination you can buy is unchanging blue-rich light. And this LED light typically delivers too little blue for daytime health, and far too much blue for the evening hours.
There are exceptions. In Chapter 10 How to be a Smart Consumer, and Chapter 11 When You Don’t Control the Space, I will show you how to find lights to provide the lighting you need to promote and protect circadian health. However, circadian lighting is still a very small fraction of the lighting market.
A recent market research surveyestimated the global circadian lighting market at $261 million, as compared to the total worldwide lighting market of $134 Billion per year. This represents only a 0.2% market share, and even that is an overestimate because they used an overly generous interpretation of what constitutes circadian lighting. For example, they counted white color tuning as “circadian lighting” where high color temperature light is provided during the day and low color temperature light in the evening. As we will discuss in Chapter 8: Creating Healthy Circadian Light merely changing the color or coordinated color temperature (CCT) of light does not usually provide effective circadian light.
Why do so few lights support circadian health?
When lighting manufacturers, lighting designers and salespeople are asked why fewer than 0.2% of the lights sold today have any circadian or healthy features, they typically have three answers.
1. Lack of Consumer Demand
First, the lighting industry will tell you that their customers are not asking for circadian lights.
You ask whose idea it was to use blue LEDs to light the world at night? The answer is the consumer. There have been so many innovations over the years in LED lighting where we thought we were providing a new benefit that would drive sales and give our products market differentiation. If it didn't lower the cost of the device for the consumer, it didn't get traction. If the modifications can be made with little or no cost impact for the consumer, it has a chance. Stand in the aisle at Home Depot and ask someone buying light bulbs what the Lighting Facts label tells them and how it informs their purchasing decision. I'll bring the bucket of ice cold water to pour on you :) Lighting product developer.
This is true because the only features that consumers have been taught to look for when choosing lights are 1) cost, 2) color, and 3) energy efficiency (in order of priority). Most people are quite unaware of the adverse health impacts of the wrong light at the wrong time.
This is why I have written THE LIGHT DOCTOR to create widespread awareness of the electric health havoc that modern lighting is creating, and to explain why you must demand healthy circadian lights to safeguard your and your family’s health.
2. Single-Minded Focus on Energy Efficiency
Second, the lighting industry will tell you that new energy regulations force them to focus on energy efficiency, and not on healthy lighting.
The Biden-Harris Administration, through the U.S. Department of Energy (DOE), today proposed stronger efficiency standards for light bulbs, also known as general service lamps, to conserve energy and cut energy bills for American families and consumers … (This) represents a key pillar of the President’s strategy to tackle the climate crisis while lowering costs for families…. Today’s proposed rule significantly raises the minimum lightbulb efficiency level, from 45 to over 120 lumens per watt for the most common bulbs. Press release US Department of Energy December 19, 2022
To comply with the 120 lumens per watt proposed regulations of the US Department of Energy, manufacturers must use blue-chip LEDs. A similar 120 lumens per watt standard is planned by the European Union. And in the United Kingdom their proposed minimum energy performance for lighting is the highest in the world, at 120 lumens per watt beginning in September 2023 and climbing to 140 lumens per watt in 2027. These standards are currently not possible to achieve with spectrally-engineered lights that regulate blue emissions across day and night to provide circadian health and performance.
Why are the regulators forcing upon us a future of harsh blue-rich LED lights? It is because they have adopted flawed metrics such as lumens per watt which measure the brightness of light and not its healthiness. They justify the regulations based on the reduction of greenhouse gases, and reduction of pollution but fail to recognize the much larger immediate human health costs and impact on the natural environment of expanding the use of blue-rich light at night.
It is clear we need to do a much better job at educating our politicians and regulators. You and I have a right to healthy light! The climate lobby has been very effective at communicating their message. We need to do a better job of communicating ours.
3. Science is Not Ready
Third, the lighting industry will tell you the science of circadian lighting is not yet proven, or is contradictory. This is partly an excuse by the industry to procrastinate on circadian lighting, and partly a failure of the scientific community to communicate how well established is the core science of circadian clocks and light.
“The reason … circadian lighting is not penetrating in the market is that nobody knows about it. Scientists know, but they only talk to each other. If you talk to your neighbor, they won’t know.” Jan Denneman, chairman of Good Light Group, an Eindhoven, Holland–based nonprofit advocating healthy lighting
In Chapter 4: Human Light Interaction, I was careful to distinguish between validated science, versus misinformation and marketing hype regarding the so-called “blue light hazard”. So, the obvious question you might ask is how can I prove that what I am saying in this book is based on rigorous scientific evidence? Am I the lone advocate of my own opinions on lighting, or am I reporting on the consensus opinion of the leading scientists in the field of circadian rhythms, light and health?
These are fair questions, so I addressed them by seeking the help of 248 of the world’s leading scientists in this field. Together we identified a series of statements that summarize what the science of circadian rhythms and light has so far firmly established.
SCIENTIFIC ASIDE: How We Established a Scientific Consensus
First, I recruited the help of three leading scientists to create a list of potential scientific statements. Professor David Blask of Tulane University has done pioneering research on the carcinogenic effects of light on breast cancer and prostate cancer. Professor Sean Cain of Monash University in Australia has done important research on the effects of light on people living their regular lives. Professor Randy Nelson of the Rockefeller Neuroscience Institute at West Virginia University has shown how exposure to light at night increases body mass gain and depressive-like responses, as well as impairs cognition, immune function, and recovery from cardiac arrest and stroke.
Together we composed a set of 40 statements laying out some of the core conclusions that could be potentially made from the 30,000 peer-reviewed scientific articles published on the science of light and circadian rhythms. To avoid the bias of only picking scientists who agreed with our opinions, we invited every scientist in the world who had published more than four peer-reviewed scientific papers on circadian rhythms and light since 2008 to assess the 40 statements. Using the comprehensive PubMed database of scientific articles to search for all papers with the terms “circadian” + “light”, we googled every scientific author with four or more publications to collect their email addresses from their university or publications websites.
248 leading scientists from around the world, all of whom are experts on the effects of light on circadian rhythms, responded to our invitation to evaluate each of the 40 statements. For each statement they indicated whether there was no evidence, limited evidence, or good scientific evidence to support it, or that the statement was scientifically well established. When the results were compiled, we found the scientists had reached a consensus on the following 25 statements that were firmly based on scientific evidence. The complete research results are available as a pre-printand are currently undergoing peer review by a scientific journal.
THE LIGHT DOCTOR is a reader-supported publication. To support our important educational mission to educate the world about healthy and unhealthy light, please consider becoming a free or paid subscriber.
Scientific Consensus on Circadian Lighting
Consensus was reached on the following 25 statements among the 248 leading scientists, who had between them published 2,697 peer-reviewed scientific publications on circadian clocks and light since 2008. Publishing an article in a peer-reviewed journal is a high standard in science which is not easily achieved as it means the research findings and conclusions have been critically examined and accepted by other scientists.
1. Robust circadian rhythms are important for maintaining good health.
Circadian rhythms are most robust when they are tightly synchronized to the natural day-night cycle, and the circadian clocks throughout the body are tightly synchronized with each other. Circadian rhythms under these conditions typically show the greatest amplitude (widest swing between daily maximum and minimum levels). When circadian rhythms are robust, sleep during the night is most restorative, mood, alertness and cognitive performance during the day are enhanced, and the immune system’s capability to ward off disease is strongest.
2. Disrupting circadian rhythms can cause ill-health.
There is a broad scientific consensus that disrupting the human circadian clock system precipitates a wide range of medical disorders as I discussed in Chapters 1: Edison’s Cancer Epidemic and 2: Goodbye Milky Way. Circadian disruption can have many different types of significant adverse health effects in children, young adults and in the elderly.
3. Regular daily exposure to daylight enhances circadian entrainment and strengthens circadian rhythms.
Getting outside at a regular time each day, especially in the mornings, and being exposed to natural daylight, is well established as an effective way to keep our circadian rhythms firmly synchronized. In the absence of regular exposure to daylight, our circadian rhythms can become dissociated and flattened and ill-health and susceptibility to disease can result. Regular exposure to daylight strengthens our circadian rhythms and tightens their entrainment by the natural cycle of day and night.
4. Regular daily exposure to daylight can enhance sleep at night.
As we discussed in Chapter 2: Goodbye Milky Way, the average person spends over 90% of their time indoors under twilight levels of lighting. The lack of a strong contrast in light exposure between day and night is a major contributor to the sleep problems that are so common today. Regular daily exposure to outdoor sunlight, or even cloudy overcast daylight, helps deepen and extend our uninterrupted nocturnal sleep.
5. Increasing indoor light intensity during daytime can enhance circadian entrainment and strengthen circadian rhythms.
Since we tend to live indoors in twilight levels of light, our circadian rhythms can become dampened and lose their tight associations with natural day and night. Increasing the brightness of indoor light during daytime hours, especially if it is rich in blue wavelengths, helps to compensate by synchronizing our circadian rhythms to the natural day-night cycle – a process called entrainment. At the same time the entrained circadian rhythms show an increased amplitude – a greater contrast between peak and trough of the daily rhythm.
6. Increasing indoor light intensity during daytime can improve daytime alertness and reduce sleepiness.
Natural light from offices with windows, and bright electric light indoors, especially when it has significant blue content, has an alerting effect, and reduces sleepiness. This combats the natural tendency to drowsiness when we live under twilight conditions.
7. Increasing indoor light intensity at night increases the disruption of circadian rhythms.
Our eyes and brain are highly sensitive to light during the nighttime hours (from sunset to sunrise), and the disruptive effects on our circadian rhythms get more pronounced the brighter the light intensity. This effect is exacerbated by lights with high blue content such as LEDs or fluorescent lights.
8. Increasing indoor light intensity at night increases the suppression of nocturnal melatonin production.
Melatonin is the pineal hormone that plays an important role in signaling the darkness of night to all the cells of the body and their internal circadian clocks. When we live outdoors in the natural world, as we discussed with the Rocky Mountain campers in Chapter 2: Goodbye Milky Way, melatonin rises at sunset and falls at dawn. But when we use electric lights, we suppress the melatonin signal and may shift it. Our internal circadian clocks interpret electric light at night as a shift in the timing of day and night. The brighter the electric light at night the more suppressed and shifted is the melatonin rhythm.
9. Repetitive and prolonged exposure to light at night bright enough to cause circadian disruption increases the risk of breast cancer in women.
As we discussed in Chapter 1: Edison’s Cancer Epidemic, the first reports were published in 2000 showing a significantly increased risk of breast cancer in women exposed to light on the night shift. Since then, several national and international scientific bodies have reviewed the considerable accumulated evidence from hundreds of human epidemiological and animal model studies. After reviewing all the evidence, the WHO International Agency for Research on Cancer, and the National Toxicology Program of US National Institutes of Health have linked light exposure at night to circadian disruption and to the significant increase in the rate of new breast cancer cases.
10. Repetitive and prolonged exposure to light at night bright enough to cause circadian disruption increases the risk of obesity and diabetes.
A substantial body of evidence has accumulated in recent years showing up to twice the risk of obesity and diabetes in people who are exposed to light at night, either by leaving the lights on in the bedroom at night, or by working on night shifts. As we discussed in Chapter 2: Goodbye Milky Way, these effects can start developing even after only one night of light exposure.
11. Repetitive and prolonged exposure to light at night bright enough to cause circadian disruption increases the risk of sleep disorders.
Light at night has three key effects on sleep. First it alerts and stimulates our brain which makes it harder to fall asleep or stay asleep. Second it shifts our circadian clocks so the timing of when we can easily fall asleep is shifted. Third it disrupts our circadian clocks and the architecture of the various sleep stages such as REM and non-REM sleep, so that sleep is disrupted and not as fully restorative.
12. The sensitivity peak of the ipRGC melanopic receptors in the human retina is approximately 480nm in the blue part of the visible spectrum.
As we discussed in Chapter 3 : Clockwork Blue, a major breakthrough in circadian science was the discovery of the intrinsically photosensitive retinal ganglion cell (ipRGC) receptors in the eye that detect the blue wavelengths in light. The peak sensitivity of these ipRGC receptors is to sky-blue light at about 480 nm.
13. The most potent wavelengths for circadian entrainment are 460-495 nm blue light near to the sensitivity peak of the ipRGC melanopic receptors.
While the ipRGC receptors have their peak sensitivity at about 480 nm, they can sense a broader range of blue light photons. Blue light is most potent in synchronizing human circadian clocks to the environmental day-night cycle, a process called “entrainment”, in the 460-495 nm range near the 480 nm peak sensitivity.
Blue-enriched (460-495nm) light in the evening (during the three hours before bedtime) …
disrupts nocturnal sleep more than blue-depleted light at the same intensity
phase delays the circadian system more than blue-depleted light at the same intensity.
disrupts circadian rhythms more than blue-depleted light at the same intensity.
When you are exposed to light containing potent 460-495 nm blue wavelengths in the evening after sunset, it shifts and disrupts your circadian rhythms and impairs your sleep at night. As we will discuss in Chapter 8: Creating Healthy Circadian Light we are sensitive to an even broader range of 440-495nm blue during overnight hours. The solution is to use blue-depleted light at night – i.e. light without those disruptive blue wavelengths – rather than conventional LED lights which are rich in blue. This greatly reduces the risk of shifting our circadian clocks, and disrupting our sleep.
17. Exposure to 460-495nm blue light at night suppresses melatonin production.
Because we are so sensitive to blue light at night, a broad range of blue wavelengths can suppress pineal melatonin production. The strongest suppression occurs with blue light wavelengths between 460 and 495 nm. These blue wavelengths interfere with the signaling of natural darkness by melatonin and undermine the important protective effects of melatonin at night, such as suppressing cancer cells in the body, as we discussed in Chapter 1: Edison’s Cancer Epidemic.
18. Exposure to 460-495nm blue light at night disrupts circadian rhythms.
These same 460 - 495 nm blue wavelengths during the nighttime hours have the largest effect in disrupting circadian rhythms. These blue wavelengths are 25 times more potent than full spectrum white light which contains all the wavelength of the visible light spectrum. Exposure to even a small amount of blue light at night is highly disruptive to circadian rhythms.
The 248 scientific experts were then asked about the practical implications of the well-established science of circadian-light interactions and reached a consensus on the following statements:
19. Light used in the evening (during the three hours before bedtime) should have as little blue content as practically possible.
We become increasingly sensitive to the blue content in our electric lights as the evening progresses. Thus, it is important to replace your lights in the places you spend your evenings, such as the family room, bathroom and bedroom, with lights that have very little or no blue content. We will discuss how to do that in later chapters of THE LIGHT DOCTOR.
20. The risk of circadian disruption during the three hours before bedtime can be reduced either by 1) dimming indoor lighting which may compromise the ability to perform visual work tasks, or 2) reducing the blue content of indoor lighting maintained at the intensity required for visual tasks.
There are two ways of addressing the problem with blue-rich light during the evening hours. Since what matters is the total number of blue photons that you are exposed to per second, you can dim your existing conventional lights significantly to reduce the total amount of light to which you are exposed. The problem is that this may make it hard to read, or difficult for your children to do their homework. Alternatively, you can replace your current lights with low blue content lights so you can maintain illumination at your preferred levels.
21. The blue content of light entering the eyes is much more important in determining circadian health outcomes than the correlated color temperature (CCT) of the light source.
Changing the color of lights, measured as correlated color temperature or “CCT”, has been touted by the lighting industry as a way to reduce blue content. Unfortunately, this is a highly misleading marketing strategy which does very little to address the problem. At the key 460 - 495 sky-blue wavelengths high CCT and low CCT electric lights can have very little difference in blue content, as they are all based on blue-pump LEDs. It is far more important to know the blue content of the lights that you are using than their CCT or color appearance.
22. Increasing the energy efficiency of lights is desirable, but not if it increases the risks of causing circadian disruption and serious illness.
Since the widespread introduction of LED lights in 2013, the lighting industry has been focused on promoting and improving the energy efficiency of LEDs. It has been the key selling proposition which has enabled blue-enriched LEDs to dominate the lighting market. While maximizing energy efficiency is, of course, desirable, failing to address the adverse health impact of energy-efficient blue-enriched LEDs is a much more significant problem. These blue-rich LEDs can increase your exposure to blue light at night, and accelerate the electric circadian havoc and ill-health caused by electric light.
23. LED lights with high 460 - 495nm blue content should carry the warning label “maybe harmful if used at night”
There was strong consensus among the 248 leading scientists researching the impact of light on circadian rhythms, that the evidence is now clear than blue-enriched LED lights with high 460 - 495 nm blue light content should carry a hazard warning label related to their use at night. This is justified by the increased risk of obesity, diabetes, heart disease and several types of cancer that are associated with exposure to excessive blue wavelengths at night.
24. There is now sufficient evidence to support the widespread introduction of circadian lighting that adjusts light intensity and blue content across day and night to maintain robust circadian entrainment and health.
There was also strong consensus that the lighting industry needs to transition to circadian lighting where the brightness of light and its blue content are varied by time of day. During the daytime hours indoor lights should be rich in sky-blue wavelengths, and during the nighttime hours from sunset to sunrise these sky-blue wavelengths should be removed.
25. There is significant variation in individual sensitivity to light, therefore circadian lighting should be optimized where possible using personalized solutions.
Some people are much more sensitive to the blue content of light than others, and it is important to adjust the blue content in electric lighting to make allowance for these more sensitive people. Furthermore, the orientation of our circadian clocks in relation to day and night may differ somewhat between individuals. Some of us are early rising “larks” and then fall asleep earlier in the evening. Others are genetically more sensitive to blue rich light in the evening and their sleep patterns may be delayed. As we discussed in Chapter 2: Goodbye Milky Way, these differences between people are reduced by regular exposure to natural outdoor light during the day.
You Have the Right to Healthy Light
As consumers of lighting, you should demand the right to have healthy lights in your homes, workplaces, schools and hospitals and everywhere else you frequent.
We can dismiss the claims by the lighting industry that the science is not ready. Our survey of the 248 leading scientists debunks these claims and provides an urgency to implementing healthy lighting.
In the following chapters I will show that we can create and validate circadian lighting which provides the health and well-being which is our right.
In this chapter you have learned:
1. The lighting industry justifies their failure to provide circadian lighting that varies brightness and blue content by time of day because a) customers are not asking for circadian lights and b) by falsely claiming the science is not yet proven, or is contradictory.
2. A survey of 248 of the world’s leading scientists researching the impact of light on circadian rhythms and health, confirms that the science explained in THE LIGHT DOCTOR is well validated, and that there is an urgent need to replace harmful blue rich LEDs at night with healthy circadian lighting.
3. You have the right to healthy light and need to campaign for it everywhere you spend your time indoors.
THE LIGHT DOCTOR is a reader-supported publication. To support our important educational mission and receive full access to this book and its references and supporting materials please consider becoming a paid subscriber for no more than you would pay in a bookstore.
Preview of next post: Chapter 6: Bringing the Outside In.
“The history of architecture is the history of the struggle for light” as Le Corbusier, the revolutionary architect wrote in 1927. Before electric light, every building had to rely on natural light during the day since candles, oil lamps and fires were impractical and too expensive to be used all day long. It was a constant struggle to balance the excessive glare from beams of direct sunlight on sunny days, with the steep drop in the brightness of daylight the further you stood from a window. After the invention of electric light, architecture tried to free itself from dependence on natural light and that has caused the unhealthy round the clock electric twilight we live in today.
I release a new chapter of THE LIGHT DOCTOR every two weeks by email to my subscribers. The email version will not contain any url reference links, as that can trigger spam filters. The version of the chapter with full references and footnotes will then be uploaded to the Substack website within a week.
I also release a podcast version of each chapter in two parts within a few days after the emailed text version.
I look forward to your comments. There is much to discuss!
Thanks for joining this conversation.
Databridge Market Research (2022) Global Circadian Rhythm Lighting Market by Regions 2023 - 2030 https://www.databridgemarketresearch.com/reports/global-circadian-rhythm-lighting-market
Full references and footnotes are uploaded to the Substack website version of this chapter within a week after its initial email distribution.
The global lighting market size was $118.33 billion in 2019 with a CAGR of 4.3% providing an estimate of $134 Billion for 2022. Fortune Business Insights, https://www.fortunebusinessinsights.com/industry-reports/lighting-market-101542 Archived at https://perma.cc/2QXZ-XGGT
US Department of Energy (2022) Biden-Harris Administration Proposes Raising Efficiency Standard for Light Bulbs. December 19, 2022 https://www.energy.gov/articles/biden-harris-administration-proposes-raising-efficiency-standard-light-bulbs Archived at https://perma.cc/7ZBA-9NAZ
Commission Regulation (EU) 2019/2020 of 1 October 2019 laying down ecodesign requirements for light sources and separate control gears pursuant to Directive 2009/125/EC of the European Parliament and of the Council and repealing Commission Regulations (EC) No 244/2009, (EC) No 245/2009 and (EU) No 1194/2012 https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=uriserv%3AOJ.L_.2019.315.01.0209.01.ENG&toc=OJ%3AL%3A2019%3A315%3ATOC Archived at https://perma.cc/8KWN-QATM
UK Department for Business Energy and Industrial Strategy (2023) New ecodesign requirements for lighting products. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1132532/new-ecodesign-requirements-for-lighting-products.pdf Archived at https://perma.cc/3XVC-TSEH
Halper M. (2022) Circadian pioneer says we’re not ready for circadian lighting. Does he really mean it? https://www.ledsmagazine.com/lighting-health-wellbeing/article/14232844/circadian-pioneer-says-were-not-ready-for-circadian-lighting-does-he-really-mean-it-magazine.