AMA – Reports of the Council on Science and Public Health
LIGHT POLLUTION: ADVERSE HEALTH EFFECTS OF NIGHTTIME LIGHTING
HOUSE ACTION: RECOMMENDATIONS ADOPTED AS FOLLOWS AND
Current AMA Policy H-135.937 (AMA Policy Database) advocates for light pollution control and reduced glare from (electric) artificial light sources to both protect public safety and conserve energy. Lighting the night has become a necessity in many areas of the world to enhance commerce, promote social activity, and enhance public safety. However, an emerging consensus has come to acknowledge the effects of widespread nighttime artificial lighting, including the:
- impact of artificial lighting on human health, primarily through disruption of circadian biological rhythms or sleep;
- intersection of ocular physiology, vehicle headlamps, nighttime lighting schemes, and harmful glare;
- energy cost of wasted and unnecessary electric light;
- impact of novel light at night on wildlife and vegetation.
In addition to these health and environmental effects, an esthetic deficit is apparent with the progressive loss of the starry night sky and interference with astronomical observations.
24 Hours Circadian Biological Rhythm is in Virtually All Life Forms
The solar cycle of light and dark provides the essential basis for life on Earth. Adaptation to the solar cycle has resulted in fundamental molecular and genetic endogenous processes in virtually all life forms that are aligned with an approximately 24-hour period (circadian biological rhythm). The circadian genetic clock mechanism is intimately involved in many, if not most, facets of cellular and organismal function. 1 Although the circadian system spontaneously generates near-24-hour rhythms, this master clock must be reset daily by the light-dark cycle to maintain proper temporal alignment with the environment.
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Disease Connections due to Disrupted Circadian Rhythms and Sleep has Expanded
The power to artificially override the natural cycle of light and dark is a recent event and represents a man-made self-experiment on the effects of exposure to increasingly bright light during the night as human societies acquire technology and expand industry. At the same time, increasing numbers of people work inside buildings under electric lighting both night and day. Artificial lighting is substantially dimmer than sunlight and provides a very different spectral irradiance. As the research on the biology of circadian rhythms has advanced, the range of potential disease connections due to disrupted circadian rhythms and sleep has expanded.
Light is the most powerful stimulus and Melatonin as Biomarker
Light is the most powerful stimulus for regulating human circadian rhythms and is the major environmental time cue for synchronizing the circadian clock. In addition to resetting the circadian pacemaker, light also stimulates additional neuroendocrine and neurobehavioral responses, including suppression of melatonin release from the pineal gland, directly alerting the brain, and improving alertness and performance. 7-9 Melatonin is one of the most studied biomarkers of the human physiological response to light. 10 This substance is the biochemical correlate of darkness and is only produced at night (Optogenetics – Li-Fi – Light Fidelity – Dangers of 5G LED Street Light – Phototoxicity – Smart Light).
Measures of Illumination
Luminous flux is the measure of the perceived power of light. The lumen is the standard international unit of luminous flux, a measure of the total “amount” of visible light emitted by a source, while illumination is a measure of how much luminous flux is spread over a given area (intensity of illumination). One lux is equal to one lumen/m 2 . Luminous flux measurements take into account the fact that the human eye and visual system is more sensitive to some wavelengths than others. The peak luminosity function is in the green spectral region; white light sources produce far fewer lumens.
Circadian Phase Shifts of the Melatonin Rhythm can be Evoked with Artificial Light
It is now established that when exposure of the human eye is carefully controlled, illuminance as low as 5−17 lux of monochromatic green light or 100 lux of broadband white light can significantly suppress melatonin in normal human volunteers. 12,16-18 Similarly, circadian phase shifts of the melatonin rhythm can be evoked with an illuminance of 5 lux of monochromatic blue light or <100 lux of white fluorescent light, however, exposure to red light is not disruptive. 18,19 Typical lighting in bedrooms in the evening after dusk (but before bedtime) can also suppress melatonin and delay its nocturnal surge.
In particular, both short and long-term photoreceptor adaptation can significantly modify the biological and behavioral responses to light and acutely suppress melatonin in humans. All humans, however, are not equally sensitive to light; significant individual differences exist in sensitivity to light for both neuroendocrine and circadian regulation.
Glare from nighttime lighting can create hazards ranging from discomfort to frank visual disability.
HEALTH EFFECTS OF DISRUPTED CIRCADIAN RHYTHMS
Light at Night, Melatonin and Circadian Influences on Carcinogenesis
Experimental Evidence. The majority of earlier studies in experimental models of either spontaneous or chemically induced mammary carcinogenesis in mice and rats demonstrated an accelerated onset of mammary tumor development accompanied by increased tumor incidence and number in animals exposed to constant bright fluorescent light during the night as compared with control animals maintained on a strict 12 hours light/12 hours dark cycle. 40-51
The ability of light exposure at night to stimulate tumor growth (including dim exposures) has been replicated in rat hepatoma models. 54,56-58 The reverse also is true; gradually restoring circulating melatonin by reducing initial exposure to light at night (24.5 lux) is accompanied by a marked reduction in tumor growth and linoleic acid metabolic activity to baseline rates in the breast cancer and hepatoma models. 59
The important role of melatonin as a nocturnal anticancer signal is further supported by the growth responses of human breast cancer xenografts perfused with human whole blood collected from young, healthy premenopausal female subjects exposed to complete darkness at night (e.g., high melatonin), compared with xenografts that were perfused with blood collected from the same subjects during the daytime (e.g., low melatonin). 54 The growth of xenografts perfused with blood collected during the dark was markedly reduced.
Light-at-night and circadian disruptions have been suggested to play a role in other cancers including endometrial, ovarian, prostate, colorectal, and non-Hodgkins lymphoma
Obesity, Diabetes, and Metabolic Syndrome. The modern world has an epidemic of obesity and diabetes that may be influenced by lack of sleep, lack of dark, and/or circadian disruption. 90 Non-day shift workers have a higher incidence of diabetes and obesity. 91 Epidemiological studies also show associations of reported sleep duration and risk of obesity and diabetes. 92 Circadian disruption may be a common mechanism for these outcomes and potential links between the circadian rhythm and metabolism. 93-95
Other Disorders. Although in the early stage of development, emerging evidence suggests that other chronic conditions also may be exacerbated by light at night exposure and ongoing disruption of circadian rhythms, including depression and mood disorders, gastrointestinal and digestive problems, and reproductive functions. 88
Life on the planet has evolved to accommodate the 24-hour solar cycle of light and dark. Human imposition of light at night and disruption of the natural dark-light cycle represents a dramatic change to the environment. 108 The entire spectrum of life, including animal, plant, insect, and aquatic species, is affected and in danger.
About 30% of all vertebrate species and 60% of invertebrate species on Earth are nocturnal and depend on dark for foraging and mating. 108 Documented wildlife destruction by light at night has been evident in bird species, which fly into lit buildings at night in enormous numbers when migrating, and in the disruption of migration and breeding cycles in amphibians. 108-111 The most studied case in reptiles involves sea turtle hatchlings on the coast of Florida, which historically have scurried from their nest directly to the ocean. With increased development along the coast, and attendant increased electric lighting at night, these hatchlings become confused and often migrate away from shore to the lights. Hundreds of thousands of hatchlings are believed to have been lost as a result of this stray electric lighting at night in Florida. 109 Furthermore, many billions of insects are lost to electric light annually, which reduces food availability for other species in addition to unnecessarily reducing living biomass. It is concerning that light at night also may be vector attractant for diseases such as malaria. 112
The circadian biology of plants is as robust as animals, and the impact of light at night on plant life may also be considerable due to the role of light in photosynthesis and the fact that many plants are pollinated at night. 113,114
- American Medical Association – AMA adopts guidance to reduce harm from high intensity street lights (2016)
- Recommendations – 2012 – AMA – Annual Meeting – Reports of the Coincil on Science and Public Health LIGHT POLLUTION: ADVERSE HEALTH EFFECTS OF NIGHTTIME LIGHTING (2012)
- Action of the AMA House of Delegates 2012 Annual Meeting: Council on Science and Public Health Report 4 Recommendations Adopted as Amended, and Remainder of Report filed. REPORT 4OF THE COUNCIL ON SCIENCE AND PUBLIC HEALTH (A-12)Light Pollution: Adverse H (2012)
- AMA – Public health: CSAPH reports
- OPINION of the French Agency for Food, Environmental and Occupational Health & Safety
- Influence of Daytime LED Light Exposure on Circadian Regulatory Dynamics of Metabolism and Physiology in Mice. (2019)
- Macular Degeneration & Blue Light
- Blue light: The new environmental pollution? (2017)
- Smart Street Lights & LED
- Department of Energy and Climate ChangePotential of Smart Technologies in SMEsFinal Report (2016) – Madness …
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- LED Street Lights – Major Health Concerns – Dr D Wojcik
AMA – Reports of the Council on Science and Public Health – LIGHT POLLUTION: ADVERSE HEALTH EFFECTS OF NIGHTTIME LIGHTING – 24 Hours Circadian Biological Rhythm is in Virtually All Life Forms – Gateshead Council on Dangerous LED Emitters – Disease Connections due to Disrupted Circadian Rhythms and Sleep has Expanded – Light is the most powerful stimulus and Melatonin as Biomarker – Measures of Illumination – Circadian Phase Shifts of the Melatonin Rhythm can be Evoked with Artificial Light – CANCER – Other Cancers – Other Diseases – Killing Wildlife