What Are the Real Health Benefits of Himalayan Salt Lamps?

Himalayan salt lamps have become very popular home decor accessories because of their aesthetic value and affordability. As natural crystals, they bring nature’s beauty into the home, and when crafted into lamps and illuminated, their warm pink, amber or orange glow creates a calming, tranquil and relaxing atmosphere within a room. Stunningly large pieces of Himalayan rock salt fashioned into lamps weighing several kilograms can be had for only tens of dollars, which is remarkable value for money!

Having a keen interest in personal wellbeing, when eBay Australia asked me to select some home and garden products to review, I chose the Himalayan Salt Lamp Night Light with Dimmer Switch from their Home & Garden > Home Décor > Other Home Décor category in order to take a closer look at this type of product, and to assess some of the health claims associated with salt lamps.

What is Himalayan Rock Salt?

Himalayan rock salt is a pink-coloured mineral salt mined from the Khewra Salt Mine, one of the oldest and largest salt mines in the world, located near the foothills of the Himalayas in Pakistan.

Geologically, rock salt is a sedimentary rock composed of the mineral halite, the naturally-occurring crystal mineral form of sodium chloride (chemical formula NaCl), which ranges from colourless to white in colour. Compounds such as calcium sulphate (CaSO4) and potassium chloride (KCl) can occur as natural impurities in rock salt [1]. The presence of some impurities, such as other minerals or chemical elements can change the colour of halite.

Rock salt forms in low-lying desert areas, where large volumes of seawater or water from salty lakes evaporates, and where an ongoing flow of salty water replenishes it, with very little fresh water coming in to wash it away.

The deposits of Himalayan rock salt are believed to have formed 250 million years ago from the evaporation of ancient bodies of water. Himalayan rock salt is composed of up to 98 percent sodium chloride (table salt), but also contains trace amounts of many other elements– such as potassium, magnesium, calcium, copper, phosphorus, boron, chromium, fluorine, iodine, manganese, molybdenum, selenium, and zinc. It also contains iron, which give Himalayan rock salt its pink colour.

How Are Himalayan Salt Lamps Made?

Himalayan salt lamps can vary in colour, ranging from light to medium pink, through to reddish and deep red in colour, depending on the location of the mine from which they were sourced.

Being mined minerals, they can be left in their irregularly-shaped, roughly-hewn form, or they can be sculpted into fancy geometric shapes with a very smooth finished surface.

These salt lamps are available in a range of heights and weights to suit any budget, with the smallest ones around 1 kg – 2 kg in weight, and approximately 14cm high x 8cm wide, while the largest can be up to 15 kg – 20 kg in weight, and approximately 35cm high x 22cm wide.

To turn a piece of Himalayan rock salt into a lamp, a cavity is carved into the bottom to house a lamp inside it, and a wooden base is screwed on to it, presumably with stainless steel screws which are resistant to corrosion, being in direct contact with salt.

A small incandescent lamp, with a low wattage of 15W is fitted in a spring-loaded lamp holder, which holds it in place inside the cavity of the salt lamp. This lamp is not too bright, it’s usually less than 199 lumens, which makes salt lamps ideal for use as a night light.

The lamp holder pushes securely into the cavity in the base of the salt lamp. When inserting the lamp holder, push it in deep enough so the base of the lamp holder does not touch the surface it’s sitting on, and the cord isn’t sharply kinked, but gently bent around to sit within one of the grooves cut into the edge of the wooden base. First find the best side of the lamp to display front-on, and then run the cord to the back through one of the cord channels/grooves in the base.

A well-made salt lamp may includes an inline power switch with a dimmer, allowing the light level to be adjusted to perfectly suit the room.

Here’s a close up of the power switch-dimmer control of the lamp I tested, the dial is offset to one side for use as a thumb-wheel, permitting one-handed operation.

Reviewing and Testing the Himalayan Salt Lamp

The lamp reviewed here was listed as 3 kg – 5 kg, 19cm high x 12cm wide, with a price of just under $30.

The actual weight of the product received was approximately 4.5 kg, with dimensions of 22cm high x 12cm wide, which is great, as it’s definitely leaning on the generous side.

Examining the salt lamp, it appeared very well made, and the mineral specimen itself looked to be of a decent quality, with a nice, natural rose-pink to salmon hue.

SAFETY NOTE: Always remove and inspect the incandescent bulb holder inside the salt lamp before switching it on. This one was wrapped in bubble wrap to protect the glass light bulb during shipping, but needed to be removed before the lamp could be used safely!

Testing the dimmer, the lamp could easily be adjusted from very dim to fairly bright. It wasn’t easy to to take photographs of equal brightness showing a lamp glowing at different light levels, but I think I managed it in the photos below.

Here’s the salt lamp set at minimum brightness.

This photo was meant to show the brightness at around 50% dimming, but it’s probably a fair bit brighter, as I wasn’t too precise. It’s set somewhere close to the half way mark for the sake of comparison.

In this final photo, the dimmer control is set to full brightness, with more of the inner core of the lamp visibly glowing.

To get the real feel of the ambience a salt lamp creates, it’s best to turn off all other lights, and use it as a mood light, to fill the room with its lovely warm glow, which is reminiscent of sitting around a log fire in the evening!

What About the Himalayan Salt Lamp Health Claims?

The most common health claims around Himalayan salt lamps are based on the idea that they emit negative ions, much like an air ioniser, and therefore provide benefits such as purifying the air of dust, allergens, pollutants and bacteria.

There are also claims that these negative ions neutralise electro-smog (EMF pollution or electromagnetic radiation) in the home.

Similarly, the second main area of claims are that salt lamps can purify the air due to the hygroscopic properties of salt, its ability to draw moisture from the air, and therefore, any pollutants and bacteria carried in the water vapour in the air.

How do these claims stack up when examined critically?

Well, I have do have a biomedical science background, and have studied electronics, so I can hopefully lend an informed, objective and unbiased opinion on the matter.

Let’s look at each claim in turn, and then go beyond the claims to see if there are any important benefits that the people marketing salt lamps may have missed.

Do Salt Lamps Produce Negative Ions?

There’s a very simple way to objectively test whether salt lamps produce negative ions, and put an end to all the conjecture and doubts, and that’s by using an instrument known as an air ion counter.

Electric air ionisers use high voltage to electrically charge air molecules with extra electrons, giving them a net negative charge, which turns them into negative ions. These devices will produce a barely perceptible breeze of negative ion that can actually be felt close to the emitters, or will have charged plates which collect pollutants and get covered in fine black muck, that need to be periodically cleaned, indicating that they’re working as intended.

Budget priced ion counters only provide a count of the negative ions produced when a high concentration of easily perceptible ions are being outputted by an ion-generating device, but they can’t detect low concentration of negative ions, as they’re not sensitive enough for that purpose.

Proper laboratory grade air ion counters range from around $600 to well over $2,500, so most critics who attempt to counter the salt lamp health benefit claims don’t do any actual testing because it would be cost-prohibitive to do so. Instead, they resort to inductive reasoning, which is the process of taking known facts and making generalisations, hypothesis or theories from them.

A scientifically less stringent but nevertheless useful test is to look for the effects of negative ion production . Negative ion generators clean the air by making pollutant particles electrically charged, so they stick to things around them, which pulls them out of the air, much like how electrostatic cling works. This causes a lot more dust and other particles to be deposited around the negative ion source, so it should be easy to observe this phenomenon around a salt lamp if negative ions are indeed being produced.

Is Rock Salt Hygroscopic?

The marketing claims that salt lamps produce negative ions are based on reasoning that hinges on salt being hygroscopic, meaning that it absorbs water from the surrounding air.

Salt is definitely hygroscopic, absorbing moisture from the atmosphere, it’s a known scientific fact. The US National Center for Biotechnology Information, PubChem Compound Summary for CID 5234, Sodium chloride lists its properties as “somewhat hygroscopic” [2].

This property of of Himalayan salt is quite easy to test, and I was able to demonstrate the hygroscopic properties of rock salt using the salt lamp.

In this experiment, the salt lamp was allowed to sit in a room with around 45-50% relative humidity over a week, without being switched on, and was then weighed.

As can be seen in the photograph below, when the salt lamp was first weighed, the weight was 4,529g.

After leaving the salt lamp running for three hours, it was weighed again, and the weight had dropped to 4,523g, which is a net loss of 6g.

By running the incandescent lamp inside the salt lamp, the block of rock salt gently warms up, evaporating the absorbed water.

Using a laser thermometer, I measured the temperature of the salt lamp before it was switched on, and the temperature was approximately 22°C.

After three hours of operation, the temperature was recorded at 28°C, which is only a modest 6°C above ambient room temperature. This resulted in the loss of 6g of water, which is a little over a teaspoon full, or only 0.13% of the starting weight of the salt lamp.

In humid climates, where the moisture levels in the air are exceedingly high, salt lamps turned off for long periods will absorb a lot of moisture, and will appear to be ‘sweating’, their surface will become damp, and in extreme cases, water will drip down and pool at their base. In such cases, it’s best to sit them in a dish to protect the surfaces they’re placed on.

Some people seeing the liquid beneath a salt lamp, fear that the salt is melting, but there is no way that salt can melt at any reasonable temperatures, as the melting point of sodium chloride is 800.7 °C (1474 °F), which is way hotter than any kitchen oven can ever reach [1].

Due to the hygroscopic nature of salt absorbing water, it dissolves and goes into solution. Salt which is sodium chloride (NaCl) is classed as an ionic compound, it consists of positively charged sodium ions (Na+) and negatively charged chlorine (chloride) ions (Cl-) which bind to each other, because opposite charges attract. When dissolved in water, putting it very simply, the sodium and chloride ions float around in the water. When the water evaporates, they come back together and recrystallise, and that’s how we extract sea salt from sea water, by evaporating the water out of it.

From my understanding, some people marketing salt lamps are making the assumption that when rock salt takes up water, the Na+ and Cl- ions are created, but when the water is driven out by the heat from the incandescent lamp evaporating it back into the air, negative ions are somehow liberated by that mechanism. From my understanding of the chemistry, this doesn’t sound correct, and through logical induction I would think that evaporating water from rock salt won’t produce any significant quantities of negative ions.

Can hydrated Himalayan salt produce negative ions by some other mechanism when water is driven from it? Short of measuring it with expensive test instruments, and being able to reproduce those findings, the most scientific answer is that “we don’t know”, but our inductive reasoning from known facts would lead us to hypothesise that it probably cannot do so, unless we’re missing some important fact here.

Can Salt Lamps Clean the Air by Other Means?

The other claim is that the hygroscopic nature of salt means that rock salt absorbs moisture from the air, along with the pollutants carried in it.

This is partially correct if there are fine water droplets in the air, as these can carry bacteria, viruses and water-soluble pollutants, but they’re different to humidity, which is pure water vapour in a gaseous state, and can’t carry any of these.

Fine droplets of water coming into contact with a block of salt will definitely be absorbed, and any bacteria will probably become desiccated (dried out and destroyed), as all the water will be drawn out of them due to the extremely high osmotic gradient. That’s the principle by which we use salt to preserve various foods.

Viruses usually don’t survive in high salt concentrations and are denatured as a result. Technically, a large mass of rock salt with a large enough surface area would purify the air to some degree if there was sufficient airflow over it, but the only way to ascertain if the degree of air purification was significant would be by running objective tests.

Hydrocarbon pollutants, on the other hand, which are not water soluble, would not be affected, and would remain in the air.

Can Salt Lamps Reduce Electromagnetic Radiation from Electronic and Electrical Devices?

The claim that salt lamps can reduce the effects of EMF (electromagnetic field) pollution due to negative ion production really leaves me baffled. Even if it was a certain fact that salt lamps produce lots of negative ions (like an air ioniser used to clean the air of particles and chemical pollutants), it wouldn’t follow that they could reduce EMF pollution. If they could, then air ionisers could also be used for that purpose also, but they’re not!

This theory that negative ions can reduce EMFs can easily be tested by placing an EMF meter measuring magnetic or electric fields near electrical appliances or electronic devices, then repeating the measurements with an air ioniser nearby. From my own measurements around the home, testing various appliances, the presence of a very large Ionmax ION401 tower ionic air purifier in my room did not alter the measurements in any way.

There are tried, tested and accepted ways of reducing EMFs, such as electrical shielding and magnetic shielding, which are used by the electronics industry to protect sensitive equipment, and by health-conscious people to reduce harmful EMF exposure.

The Real Health Benefits of Himalayan Salt Lamps

The most obvious feature of salt lamps is the warm pink, amber or orange light that they produce, which sits well within the warm end of the colour temperature spectrum, a scale which measures how warm (yellow) or cool (blue) the light from a particular source appears. This is actually quite significant!

Looking at the colour temperature diagram below, we can see that the tungsten lamps (incandescent lamps) like the one in the salt lamp emit a much warmer light than the sun at sunrise and sunset. Enclosing this type of lamp inside a warm-coloured, translucent mineral makes the colour of the light even warmer yet in appearance, which approximates natural light at specific times in the day.

Colour Temperature of Sunlight Changes Throughout the Day

This colour temperature diagram above also shows us that the colour of the sun changes throughout the day, and with weather conditions.

• At sunrise and sunset, the sun’s light has the warmest colour.
  
• The early morning and late afternoon sun’s light not quite as warm in colour, but fairly warm.
  
• The sun at noon (midday) tends to be close to to white in colour temperature.
  
• Bright full sun tends to cooler blue in colour, and the filtered sunlight from overcast skies take on an even more blue tone.

Photographers refer to the first hour of light after sunrise, and the last hour of light before sunset as the “golden hour”, because of the soft light and the wonderful hues of red, orange and yellow, which create dramatic and stunning light for taking landscape and portrait photos.

In contrast to warm lighting of the sunset photo above, the light from the midday sun, as shown in the photo below, is much harsher, cooler in tone, and bluish-white in colour.

This may explain why photographers get up very early in the morning, or wait around for sunsets, to capture memorable landscape photos, and avoid the harsh shadows of midday sun, but what has this got to do with health, or salt lamps? The answer is, more than you would ever imagine!

Effects of Light on Human Circadian Rhythms, Sleep, Mood and Health

The short explanation is that when our eyes are exposed to blue light, it tells the pineal gland in the brain to stop producing melatonin, the hormone which synchronises your biological clock and makes us sleepy.

The long, technical explanation:

Circadian rhythms are repeating 24-hour cycles that controls the timing of several activities and functions of your body, such as the sleep-wake cycle, body temperature, hormones, appetite, and other body functions, and are often referred to as the body’s internal clock. They are mostly affected by light and darkness, and are controlled by a small area in the middle of the brain, a group of about 20,000 nerve cells (neurons) that form a structure called the suprachiasmatic nucleus, or SCN, which serves as the ‘master clock’. The SCN is part of the hypothalamus, and receives direct input from the eyes. [3] [4]

At the back of the eyes is fine layer of nerve tissue known as the retina. It contains photoreceptors such as cones, which enable us to see colour, and rods which are only active in low light levels, allowing us to see during twilight and darker conditions.

The retina also contains retinal ganglion cells (RGC) and these photoreceptor contain melanopsin, a short-wavelength-sensitive pigment with a peak spectral sensitivity near around 480 nm, which means they respond most strongly to blue light. These photoreceptors provide the primary input into the circadian clock, by transmitting the signal to the neurons of the SCN.

Blue light has shorter waves, with wavelengths between about 450 and 495 nanometres (nm), as shown in the diagram below..

The SCN ‘master clock’ in the brain controls the production of melatonin, a hormone that is released from the pineal gland at night in response to darkness. Melatonin helps synchronize circadian rhythms (24-hour internal clock), and acts as an inhibitor to arousal and awareness, making us sleepier, thus promoting sleep. When there is less light, at night for example, SCN tells the brain to make more melatonin, so we get drowsy.[5].

That’s the end of the technical explanation!

According to the U.S. Department of Health & Human Services, Center for Disease Control (CDC), blue light has the strongest impact on circadian rhythms. White light, which is composed of all visible colours of light – red, orange, yellow, green, blue, violet, contains the colour blue even though it’s not visible. When the eyes are exposed to blue light (or white light, which includes blue light) during the sensitive periods, photoreceptors in the retina are triggered to send a signal to suppress melatonin and shift circadian rhythms, which can make it difficult for you to fall asleep and stay asleep.

It’s important to note that the photoreceptors in the eye do not respond to red light and minimally respond to yellow and orange light. This means that red light has no effect on the circadian clock, so it’s okay to use a dim red light at night. Yellow and orange light have little effect on the circadian clock so we can use a very dim yellow or orange light at night [6][7].What colour is a Himalayan salt lamp?

The amount of blue light emitted by different white lights varies depending on the technology used, as shown in the graphs below.

Exposure to white light during the daytime (which contains blue light) is important for our health too, as the blue light can have positive effects such as boosting alertness, elevating mood, improving memory and cognition.

If the underlying pattern isn’t obvious by now, I’ll spell it out. The human brain responds to the colour temperature (warm yellows or cool blues) of daylight to set us into the correct mode of functioning through the day. Our bodies increase in alertness after sunrise because the light becomes more blue, and melatonin, the relaxing, sleep-promoting hormone, get switched off. During midday, when nature wants is to be the most active, the light is at its bluest. As the evening progresses, the colour temperature of the sun’s light becomes more yellow and then red, and with the blue light gone, melatonin production can begin again when it’s dark, and nature intends us to rest.

The U.S. Department of Health & Human Services, Center for Disease Control (CDC) advises us to avoid using certain devices at night:

“Blue light waves come from fluorescent and LED lights and back-lit electronic screens on televisions, computers, tablets, and cell phones. Remember, exposure to these lighted screens during the sensitive period can make it difficult for you to fall asleep at night or can wake you up too early. Especially if you are having trouble with sleep, avoid these lights during the sensitive period.” [6][7]

What Health Problems Can Exposure to Blue Light at Night Cause

While having good sleep sounds like a common-sense healthy practice, the effects of disrupting the body’s natural circadian rhythms with artificial light can be quite drastic.

According to the U.S. Department of Health and Human Services, National Institutes of Health, National Institute of General Medical Sciences:

“Do circadian rhythms affect body function and health? Yes. Circadian rhythms can influence sleep-wake cycles, hormone release, eating habits and digestion, body temperature, and other important bodily functions. Biological clocks that run fast or slow can result in disrupted or abnormal circadian rhythms. Irregular rhythms have been linked to various chronic health conditions, such as sleep disorders, obesity, diabetes, depression, bipolar disorder, and seasonal affective disorder.”

Here is a further list of extracts from research findings on the negative health effects associated with disrupted circadian rhythms due to artificial white or blue light at night, which include increased incidences of cancer.

• “Irregular light environments lead to problems in circadian rhythms and sleep, which eventually cause mood and learning deficits. Recently, it was found that irregular light can also directly affect mood and learning without producing major disruptions in circadian rhythms and sleep.” [8]
  
• “Exposure to light from self-luminous displays may be linked to increased risk for sleep disorders because these devices emit optical radiation at short wavelengths, close to the peak sensitivity of melatonin suppression.” [9]
  
• “We found that the use of these devices before bedtime prolongs the time it takes to fall asleep, delays the circadian clock, suppresses levels of the sleep-promoting hormone melatonin, reduces the amount and delays the timing of REM sleep, and reduces alertness the following morning. Use of light-emitting devices immediately before bedtime also increases alertness at that time, which may lead users to delay bedtime at home.
  
  Overall, we found that the use of portable light-emitting devices immediately before bedtime has biological effects that may perpetuate sleep deficiency and disrupt circadian rhythms, both of which can have adverse impacts on performance, health, and safety.” [10]
  
• “Rather recently, the availability of artificial light has substantially changed the light environment, especially during evening and night hours. This may increase the risk of developing circadian rhythm sleep–wake disorders (CRSWD), which are often caused by a misalignment of endogenous circadian rhythms and external light–dark cycles. While the exact relationship between the availability of artificial light and CRSWD remains to be established, nocturnal light has been shown to alter circadian rhythms and sleep in humans.” [5]
  
• “Night shift work, exposure to light at night (ALAN) and circadian disruption may increase the risk of hormone-dependent cancers.” [11]
  
• “In conclusion, based on the current study and previous related research, the use of electronic devices at night may result in trends towards suppression of leptin levels and impaired sleep quality, with negligible differences associated with whether or not the ‘Night Shift’ feature on the iPad is initiated or not.
  
  This research has important implications for the potential link between electronic device use at night and obesity rates in young adults, however further research is required to expand on these findings in a chronic setting, with additional plasma hormonal measures (leptin, ghrelin and melatonin), greater sample sizes and greater exposure durations to blue-light.” [12]
  
• “Exposure to Artificial Light At Night (ALAN) results in a disruption of the circadian system, which is deleterious to health. In industrialized countries, 75% of the total workforce is estimated to have been involved in shift work and night work. Epidemiologic studies, mainly of nurses, have revealed an association between sustained night work and a 50-100% higher incidence of breast cancer.” [13]

How to Use Himalayan Salt Lamps for Maximum Health Benefits

The recommended ways to reduce blue light exposure at night include:

• Using blue-light-blocking glasses
• Using a red or orange reading lamp which doesn’t emit blue light
• Using candlelight
• Turning off all lights in the home 1–2 hours before bedtime
• Keeping bedrooms completely dark
• Using a sleep mask to cover eyes

A much simpler and more elegant solution is to use a Himalayan salt lamp to provide the red-orange light, and locate it in the room where the last hours of the day are spent, such as a a bedroom or study.

Recreate the natural light cycle by connecting the lamp on a timer to switch on 1 – 2 hours before bedtime to visually indicate it’s time to mentally wind down, and to allow the body to begin releasing melatonin to promote sleep.

When the salt lamp switches on, turn off all other lights. This creates an atmosphere more conducive to rest, and will help establish a healthy routine and ensure consistent bedtime.

Could we just use a warm white LED bed lamp or a red coloured LED light? Sure, but the ambience they create is rather unnatural, almost clinical, and they cost much more. Neither has the aesthetic appeal or a Himalayan salt lamp, which when switched on has light similar to candlelight, without any of the risks, and switched off, is a showy halite crystal specimen!

References

1. Mohammad, Nafees & Khan, Nazish & Rukh, Shah & Bashir, Adila. (2013). Analysis of Rock and Sea Salt for Various Essential and Inorganic Elements. 10.13140/2.1.2590.4647.
2. National Center for Biotechnology Information (2021). PubChem Compound Summary for CID 5234, Sodium chloride. Retrieved May 10, 2021 from https://pubchem.ncbi.nlm.nih.gov/compound/Sodium-chloride.
3. U.S. Department of Health and Human Services, National Institutes of Health, National Cancer Institute, NCI Dictionaries – Circadian Rhythm
4. U.S. Department of Health and Human Services, National Institutes of Health, National Institute of General Medical Sciences – Facts Sheet, Circadian Rhythms, September 2017
5. Blume C, Garbazza C, Spitschan M. Effects of light on human circadian rhythms, sleep and mood. Somnologie (Berl). 2019 Sep;23(3):147-156. doi: 10.1007/s11818-019-00215-x. Epub 2019 Aug 20. PMID: 31534436; PMCID: PMC6751071.
6. U.S. Department of Health & Human Services, CDC, The National Institute for Occupational Safety and Health (NIOSH) – NIOSH Training for Nurses on Shift Work and Long Work Hours, The Color of the Light Affects Circadian Rhythms
7. U.S. Department of Health & Human Services, CDC, The National Institute for Occupational Safety and Health (NIOSH) – Interim NIOSH Training for Emergency Responders: Reducing Risks Associated with Long Work Hours, The Color of the Light Affects the Circadian Rhythms
8. Legates, Tara & Fernandez, Diego & Hattar, Samer. (2014). Light as a central modulator of circadian rhythms, sleep and affect. Nature reviews. Neuroscience. 15. 443-54. 10.1038/nrn3743.
9. Wood B, Rea MS, Plitnick B, Figueiro MG. Light level and duration of exposure determine the impact of self-luminous tablets on melatonin suppression. Appl Ergon. 2013 Mar;44(2):237-40. doi: 10.1016/j.apergo.2012.07.008. Epub 2012 Jul 31. PMID: 22850476.
10. Chang AM, Aeschbach D, Duffy JF, Czeisler CA. Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. Proc Natl Acad Sci U S A. 2015 Jan 27;112(4):1232-7. doi: 10.1073/pnas.1418490112. Epub 2014 Dec 22. PMID: 25535358; PMCID: PMC4313820.
11. Garcia-Saenz, A., Sánchez de Miguel, A., Espinosa, A., Valentin, A., Aragonés, N., Llorca, J., Amiano, P., Martín Sánchez, V., Guevara, M., Capelo, R., Tardón, A., Peiró-Perez, R., Jiménez-Moleón, J. J., Roca-Barceló, A., Pérez-Gómez, B., Dierssen-Sotos, T., Fernández-Villa, T., Moreno-Iribas, C., Moreno, V., García-Pérez, J., … Kogevinas, M. (2018). Evaluating the Association between Artificial Light-at-Night Exposure and Breast and Prostate Cancer Risk in Spain (MCC-Spain Study). Environmental health perspectives, 126(4), 047011. https://doi.org/10.1289/EHP1837
12. Driller, M. W., Jacobson, G., & Uiga, L. (2019). Hunger hormone and sleep responses to the built-in blue-light filter on an electronic device: a pilot study. Sleep science (Sao Paulo, Brazil), 12(3), 171–177. https://doi.org/10.5935/1984-0063.20190074
13. Touitou Y, Reinberg A, Touitou D. Association between light at night, melatonin secretion, sleep deprivation, and the internal clock: Health impacts and mechanisms of circadian disruption. Life Sci. 2017 Mar 15;173:94-106. doi: 10.1016/j.lfs.2017.02.008. Epub 2017 Feb 16. PMID: 28214594.
14. Blue Light and Sleep: What’s the Connection? Healthline website, written by Kris Gunnars, BSc — Medically reviewed by Atli Arnarson BSc, PhD — Updated on May 21, 2020