Select Page

Research on Blue Light Shows Blue Light Has Harmful Biological Effects

 

According to the American Optometric Association Blue light can cause retinal damage” because “visible light passes through the media of the eye to the retina where photoreceptors transform it into an electrochemical signal. Humans depend on this process for image-formation and regulation of daily sleep-wake cycles. Commonly encountered light emitted by the sun and personal electronic devices contain significant amounts of high-energy, short- wavelength blue light. Ultraviolet (UV) light contains more energy than blue light, but is absorbed by the cornea and crystalline lens, limiting retinal exposure.”

“Visible blue light may potentially be harmful to the human retina, as it can be absorbed by the retinal pigment epithelium (RPE) and certain photoreceptors, generating localized oxidative and thermal stress. Laboratory studies on rodent and primate models have demonstrated that extended time periods of direct retinal exposure to bright blue light accelerate rates of RPE and photoreceptor death.

“With the push for higher energy efficiency and cost savings in our schools, many school districts are now switching their lighting to LED-based lighting systems. While this may be good for school budgets, it is a detriment to children’s vision.” Review on Optometry

“Insufficient light during the day and excessive light exposure during evening and night hours disrupts the human circadian timing system and may cause impaired sleep, immunity, and mood, and it is associated with increased risks of obesity and diabetes as well as breast, prostate, and other neuroendocrine-sensitive cancers. In 2010, the World Health Organization International Agency for Research on Cancer classified nightshift work with circadian disruption as a probable (group 2A) human carcinogen  and in 2018, the US National Toxicology Program expert panel concluded that circadian disruption caused by excessive light at night and insufficient light during the day is reasonably anticipated to be a human carcinogen. Yet, our modern 24/7 society depends on the use of electric lighting at night and lowered indoor illumination levels during the day. “- Moore Ede et al 2020

5/14/2019 The French Agency for Food, Environmental and Occupational Health & Safety (ANSES) has issued a new report reviewing the scientific evidence on health impacts including vision loss and damaged sleep from the blue light emitted from LED lights and the screens of cell phones, laptops and digital devices. 

 

“The new scientific data confirm the 2010 result regarding the toxicity of blue light to the eye, which can lead to failing eyesight. They show short-term phototoxic effects associated with acute exposure and long-term effects associated with chronic exposure, which increase the risk of developing age-related macular degeneration.” 

 

The report states that current ICNIRP optical radiation  limits are non protective in regards to these impacts and cites research linking blue light exposure to damage to the retina of the eye and the disturbance of sleep rhythms. ANSES also highlights that children are an especially vulnerable population as their eyes are still maturing and are unable to filter the blue light out as much as adults. ANSES posits this could lead to an increased risk of age-related macular degeneration (AMD) after chronic exposure to blue light.  AMD is  a leading cause of severe vision loss in adults over age 50. 

 

The ANSES expert appraisal shows that even very low levels of exposure to blue light in the evening or at night disrupts biological rhythms and therefore sleep. The Agency recommends limiting the use of LED devices with the highest blue-light content, especially for children and pregnant women, and reducing light pollution as much as possible to preserve the environment and protect the public.

 

Excerpts from the Report include: 

 

“The Agency confirms the toxicity of blue light on the retina and highlights the biological rhythm and sleep disruption associated with exposure to blue light in the evening or at night, particularly via screens and especially for children.”

 

“The amount of light received by the retina in the blue band can be large and have phototoxic effects on the eye and a disruptive effect on biological rhythms.”

 

“Most of the available scientific studies show that blue light alters sleep regulation via circadian disruptions. The evidence provided by studies undertaken in humans is sufficient to conclude that exposure to blue-rich light during the evening has a proven effect on sleep onset latency and the duration and quality of sleep.”

 

ANSES recommendations to limit the population’s exposure to blue light. 

    • Prefer “warm white” domestic lighting (colour temperature below 3000 K).
    • Limiting the exposure of people – children in particular – to the blue-rich light of LED screens (mobile phones, tablets, computers, etc.) before bedtime and at night.
    • Creating protected spaces, without any artificial lighting.
    • Recommendations for employers to protect workers from the phototoxic effects of blue light by  limiting the exposure of workers to these light sources and informing them of the related hazards. 
    • Recommendations to protect pregnant women: “Given the effects observed on foetal development in animals related to maternal exposure to light at night, the CES recommends limiting the exposure of pregnant women to light during the night.
    • Several susceptible population groups were identified based on research data: infants, children, adolescents and young adults, people with ocular diseases (dry eye, ARMD, glaucoma, retinopathy, etc.); people with motor or cognitive disorders reducing their avoidance or decision-making capacities in the event of overly intense light; people taking photosensitising medications or exposed to photosensitising pollutants, and night workers  and any other professionals with potentially high exposure to LED lighting (surgeons, dentists, lighting professionals, lighting distributors, performing artists, people working in sport facilities, people working in agri-food facilities using LEDs (greenhouses, aquaculture), etc.).
    • Revising the exposure limits for optical radiation proposed by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) so  the limits account for chronic exposure and be sufficiently protective against phototoxic risks.
    • Adapting a new regulatory framework for all LED systems 

 

  • Restrict the sale of LED objects to the general public to those in higher risk groups.
  • Limit the light intensity of vehicle lights, while guaranteeing road safety.
  • Minimise the temporal modulation of the light emitted by all light sources (lighting, screens, other LED objects).
  • Establishing standards for protective equipment purporting to protect consumers from blue light such as blue light blocking  lenses, protective eye glasses and  computer screen coverings.
  • ANSES stated that the scientific knowledge consistently shows an increase in mortality and a decline in the diversity of the animal and plant species linked to night lighting and LEDs. Regulations to limit light pollution should be strengthened,  while ensuring public safety.

2022 Study: Oriented migratory flight at night: Consequences of nighttime light pollution for monarch butterflies: iScience

  • Nighttime light pollution can disturb diurnal migratory monarch butterflies, Exposure to this pollution induces abnormal activity in normally quiescent monarchs, This pollution acts as sensory noise that perturbs the circadian clock of monarchs, Conservation should consider susceptibility of habitat to nighttime light pollution.

“Researchers found that butterflies roosting at night near artificial illumination such as a porch or streetlight can become disoriented the next day because the light interferes with their circadian rhythms. Artificial light can impede the molecular processes responsible for the butterfly’s remarkable navigational ability and trigger the butterfly to take wing when it should be resting.”-Lights can interfere with monarch butterfly’s navigation abilities | University Of Cincinnati

 

 

Light at Night

In 2021, the National Toxicology Program  “Review of Shift Work at Night, Light at Night, and Circadian Disruption” concluded there was  “high confidence that persistent night shift work that disrupts circadian rhythms can cause breast cancer in women and may cause prostate cancer in men” and “moderate confidence for a causal relationship between human cancer and certain lighting conditions that cause circadian disruption. Certain lighting conditions are defined as excessive LAN exposure combined with insufficient daylight exposure.”

SCIENCE TO KNOW

Meng Q , Lian Y , Jiang J , et al. Blue light filtered white light induces depression-like responses and temporary spatial learning deficits in rats. Photochem Photobiol Sci. 2018;17(4):386-394. doi:10.1039/c7pp00271h

  • Blue filtered light induces depression-like symptoms and temporary spatial learning deficits in rats, which might be closely related to the impairment of light-evoked output signals in the retina.

 

Heo JY, Kim K, Fava M, et al. Effects of smartphone use with and without blue light at night in healthy adults: A randomized, double-blind, cross-over, placebo-controlled comparisonJ Psychiatr Res. 2017;87:61-70. doi:10.1016/j.jpsychires.2016.12.010

  • “This study investigated the immediate effects of smartphone blue light LED on humans at night. We investigated changes in serum melatonin levels, cortisol levels, body temperature, and psychiatric measures with a randomized, double-blind, cross-over, placebo-controlled design…”
  • “use of blue light smartphones was associated with significantly decreased sleepiness (Cohen’s d = 0.49, Z = 43.50, p = 0.04) and confusion-bewilderment (Cohen’s d = 0.53, Z = 39.00, p = 0.02), and increased commission error “

 

Nakashima Y, Ohta S, Wolf AM. Blue light-induced oxidative stress in live skin. Free Radic Biol Med. 2017;108:300-310. doi:10.1016/j.freeradbiomed.2017.03.010

  • Exposing human skin to the blue light contained in sunlight depressed flavin autofluorescence, demonstrating that the visible component of sunlight has a physiologically significant effect on human skin. The ROS produced by blue light is probably superoxide, but not singlet oxygen. These results suggest that blue light contributes to skin aging similar to UVA.

Janků K, Šmotek M, Fárková E, Kopřivová J. Block the light and sleep well: Evening blue light filtration as a part of cognitive behavioral therapy for insomniaChronobiol Int. 2020;37(2):248-259. doi:10.1080/07420528.2019.1692859

  • We provide further evidence that blocking short-wavelength light in the evening hours may be beneficial for patients suffering from insomnia.

Circadian Potency Spectrum with Extended Exposure to Polychromatic White LED Light under Workplace Conditions

 

Nash, T.R., Chow, E.S., Law, A.D. et al. Daily blue-light exposure shortens lifespan and causes brain neurodegeneration in Drosophila. npj Aging Mech Dis 5, 8 (2019).  

  • Blue light induces expression of stress-responsive genes in old flies but not in young, suggesting that cumulative light exposure acts as a stressor during aging. We also determined that several known blue-light-sensitive proteins are not acting in pathways mediating detrimental light effects. Our study reveals the unexpected effects of blue light on fly brain and establishes Drosophila as a model in which to investigate long-term effects of blue light at the cellular and organismal level.

Light at Night

Dong Zhang, Rena R Jones, Peter James, Cari M Kitahara, Qian Xiao. Associations between artificial light at night and risk for thyroid cancer: A large US cohort study. Cancer. 2021 Feb 8. doi: 10.1002/cncr.33392. 

  • Among 464,371 participants, a positive association was found between LAN and thyroid cancer risk… In women, the association was stronger for localized cancer, whereas in men, the association was stronger for a more advanced stage. Results were consistent across different tumor sizes.

Ariadna Garcia-Saenz et al, Evaluating the Association between Artificial Light-at-Night Exposure and Breast and Prostate Cancer Risk in Spain (MCC-Spain Study), Environmental Health Perspectives (2018). DOI: 10.1289/EHP1837

  • The study was conducted within the framework of the MCC-Spain project, and includes medical and epidemiological data of more than 4,000 people between 20 and 85 years of age in 11 Spanish regions. Indoor exposure to artificial light was determined through personal questionnaires, while outdoor levels of artificial light were evaluated for Madrid and Barcelona, based on nocturnal images taken by astronauts aboard the International Space Station.
  • Results obtained for both cities show that participants exposed to higher levels of  had a 1.5 and two-fold higher risk of developing breast and , respectively, as compared to the less-exposed population.

Garcia-Saenz, Ariadnaa–c; de Miguel, Alejandro Sánchezd–g; Espinosa, Anaa–c,h; Costas, Laurab,i; Aragonés, Nuriab,k; Tonne, Cathryna–c; Moreno, Victorb,i,j,l; Pérez-Gómez, Beatrizb,m; Valentin, Antoniaa,c,h; Pollán, Marinab,m; Castaño-Vinyals, Gemmaa–c,h; Aubé, Martinf; Kogevinas, Manolisa–c,h Association Between Outdoor Light-at-night Exposure and Colorectal Cancer in Spain, Epidemiology: September 2020 – Volume 31 – Issue 5 – p 718-727

  • We investigated the association between exposure to ALAN according to light spectrum and colorectal cancer among subjects who had never worked at night in a general population case–control study in Spain.
  • Exposure to blue light spectrum was positively associated with colorectal cancer (OR = 1.6; 95% CI: 1.2–2.2; highest vs. lowest tertile).
  • Outdoor blue light spectrum exposure that is increasingly prevalent in recent years may be associated with colorectal cancer risk.
  • See video abstract: http://links.lww.com/EDE/B708.

 

Höhn C, Schmid SR, Plamberger CP, Bothe K, Angerer M, Gruber G, Pletzer B, Hoedlmoser K. Preliminary Results: The Impact of Smartphone Use and Short-Wavelength Light during the Evening on Circadian Rhythm, Sleep and Alertness. Clocks & Sleep. 2021; 3(1):66-86. https://doi.org/10.3390/clockssleep3010005

  • “There is growing evidence that short-wavelength light affects hormonal secretion, thermoregulation, sleep and alertness. ..Cortisol was elevated in the morning after reading on the smartphone without a filter, which resulted in a reduced cortisol awakening response. Evening melatonin and nightly vasodilation (i.e., distal-proximal skin temperature gradient) were increased after reading on printed material. Early slow wave sleep/activity and objective alertness in the morning were only reduced after reading without a filter. These results indicate that short-wavelength light affects not only circadian rhythm and evening sleepiness but causes further effects on sleep physiology and alertness in the morning. Using a blue light filter in the evening partially reduces these negative effects.”

Safety at Home

Reduce the Blue Light From All Screens

Blue light is well understood to impact our sleep and worse, it can damage the eyes, especially children’s eyes as they are more vulnerable. Light at night is linked to cancer and can cause or worsen many health problems because it robs us of the natural healing that happens during deep sleep. Many health authorities recommend we eliminate and reduce blue light to protect our health. Practical steps include:

  • Use a blue light blocker covering for all your computer/laptop/tablet screens including cell phones.
  • Use blue-blocking glasses when you are working on the computer (This does not protect the skin.) 
  • Some people will use a blue light blocker (which is a thin film that sits unnoticeable over the screen) and then also a 100% blue blocker of hard thick plastic at night. However, be aware that many of the thinner unnoticeable blue light coverings on the market do not protect 100% blue light.
  • Download a program (like Iris) onto your device that will automatically reduce blue light at night. 

Shopping list

Support our nonprofit by shopping with these affiliate links. This allows us to continue to spread awareness and provide resources. We only share items that EHT staff uses. 

American Medical Association

The American Optometric Association

Review of Optometry

Learn the science and key clinical points to help educate—and ultimately protect—your patients.

Soft Lights

International Dark-Sky Association

The French Agency for Food, Environmental and Occupational Health & Safety (ANSES) Report 

 

Additional Resources 

The International Agency for Cancer Research (IARC) classified shift work that involves circadian disruption as a “probable carcinogen in  2007 

National Toxicology Program: Shift work at Night, Artificial Light at Night, and Circadian Disruption Workshop

NIH: Artificial light during sleep linked to obesity

Environmental Health Perspectives: LIGHT POLLUTION: Light at Night and Breast Cancer Risk Worldwide

Outdoor Light at Night and Breast Cancer Incidence in the Nurses’ Health Study II

Hidden Blue Hazard? LED Lighting and Retinal Damage in Rats. Environmental Health Perspectives 2014. https://ehp.niehs.nih.gov/122-a81/

 

News Articles

Doctors issue warning about LED streetlights, CNN, 2016.  

What Is All of That Screen Time Doing to Your Skin?, New York Times, 2020

Daily exposure to blue light may accelerate aging, even if it doesn’t reach your eyes, Science Daily, 2019

Light Pollution Resources

Light Pollution Can Harm Wildlife – International Dark Sky

The International Dark-Sky Association

  •  Glare from Bad Lighting is a Safety Hazard

Reviews on Optometry, 2016

Seeing Blue: The Impact of Excessive Blue Light Exposure

Learn the science and key clinical points to help educate—and ultimately protect—your patients.

“Most optometrists are already aware of the impact of blue light on the different tissues and structures in the eye. In 2004, researchers found evidence suggesting the impact of blue light exposure on the risk of macular degeneration in the retina.18 This led to subsequent studies on the long-term effects of visible light on the eye. In 2013, researchers identified the most damaging visible wavelengths to be in the blue-violet range of 415nm to 455nm. These wavelengths were found to be the most harmful to cells in the eye, as they can penetrate deeper into the eye and harm the retina, particularly the retinal pigment epithelium, causing the development of a toxic, apoptosis-causing molecule called N-retinlyidene-N-retinylethanolamine (A2E) to be produced within the RPE cells, causing cell viability loss.”

Read the article HERE. 

Light Impacts Appetite Hormone

Leptin is a cell-signalling hormone critical in the regulation of appetite, food intake and body weight. Leptin is sometimes called the hunger hormone. Studies have shown that an absence of leptin in the body or leptin resistance can lead to uncontrolled feeding and weight gain. 

Driller MW, Jacobson G, Uiga L. Hunger hormone and sleep responses to the built-in blue-light filter on an electronic device: a pilot study. 12(3):171. doi:10.5935/1984-0063.20190074

  •  In a randomised, crossover design, 13 young adults use of electronic devices at night may result in moderate suppression of leptin levels and impaired sleep quality, with negligible differences associated with whether or not the ‘Night Shift’ feature is turned on.
  • Three experimental trials. Two of the interventions included one hour of night-time electronic device use; reading on an iPad ~30 cm from eyes, either with the ‘Night Shift’ blue-light filtering feature turned on or off.  The control trial involved reading a hard-copy book for one hour. 

Okuliarova M, Rumanova VS, Stebelova K, Zeman M. Dim Light at Night Disturbs Molecular Pathways of Lipid Metabolism. Int J Mol Sci. 2020 Sep 21;21(18):6919. doi: 10.3390/ijms21186919. PMID: 32967195; PMCID: PMC7555372.

  • We found lower leptin and a trend towards higher adiponectin in the circulation of rats exposed to dim light at night  compared to controls.
  • In conclusion, our data showed that chronic exposure to low-intensity light at night resulted in excessive TAG accumulation in the liver through the deregulated balance of lipid biosynthetic pathways. In dLAN-exposed rats, we found upregulated hepatic genes involved in de novo lipogenesis and elevated glucose and fatty acid uptake. 

Fonken LK, Nelson RJ. The effects of light at night on circadian clocks and metabolism. Endocr Rev. 2014 Aug;35(4):648-70. doi: 10.1210/er.2013-1051. Epub 2014 Mar 27. PMID: 24673196.

  • In this review, we propose that exposure to light at night alters metabolic function through disruption of the circadian system. We first provide an introduction to the circadian system, with a specific emphasis on the effects of light on circadian rhythms. Next we address interactions between the circadian system and metabolism. Finally, we review current experimental and epidemiological work directly associating exposure to light at night and metabolism.