In honor of International Dark Sky Week -- scheduled for 05 to 12 April 2021 -- and Global Astronomy Month, we will discuss the growing prevalence of light pollution. We will also delve into the physical, mental and emotional health impacts of light pollution -- particularly over extended periods of time. Exposure to artificial light during naturally dark hours can disrupt the body’s circadian rhythm. This can lead to bouts of interrupted sleep, negatively affect eating behavior and increase risk of certain diseases. As cities grow, highways expand and artificial light permeates homes late into the night, the skyline’s sparkle loses its appeal. Given our commitment to sustainable design, limiting our negative impact on the planet while supporting human health is incredibly important to all of us at Living Deep, but especially so to our co-founder Jason F. McLennan. In his 2004 book The Philosophy of Sustainable Design: The Future of Architecture, Jason wrote that "sustainable design...seeks to maximize the quality of the built environment, while minimizing or eliminating the negative impact to the natural environment." To learn more about the intersection between sustainable design and limiting light pollution, listen to the episode "99% Guilt Free" of the 99% INVISIBLE radio show from WNYC and PRX. The episode explains how every issue we face related to sustainability -- whether it be climate change or light pollution -- can be reframed as a design problem. Follow below to learn more about International Dark Sky Week and the health harms of light pollution.
What is International Dark Sky Week?
According to the International Dark-Sky Association’s website, Virginian high school student Jennifer Barlow founded International Dark Sky Week in 2003. Unable to view the constellations that intrigued and delighted her, Barlow was frustrated by light pollution and its impact on our appreciation of and interactions with the natural world. Quoted by Planeta.com, Barlow explained that she wanted “‘people to be able to see the wonder of the night sky without the effects of light pollution.’” Barlow felt that “‘the universe is our view into our past and our vision into the future.’” In beginning Dark Sky Week, Barlow hoped to “‘preserve its wonder.’” Though International Dark Sky Week began as a series of local activities in Barlow’s home state, it eventually morphed into a global event. Today, people around the world unplug from devices and head outside to view a sky undisturbed by artificial light at night. The IDA hopes observing the moon, stars and planets on clear nights during International Dark Sky Week will encourage participants to advocate for light pollution control all year round.
Understanding Light Pollution
Types of Light Pollution
According to the James Madison University publication “Light Pollution: The Overuse & Misuse of Artificial Light at Night,” light pollution refers to “artificial light [that] shines outward and upward into the sky, where it's not wanted, instead of focusing it downward” where it can actually be used effectively. As JMU explains, there are multiple types of light pollution -- many of which are largely unintentional. Light pollution might include “light trespass.” Light trespass occurs when “unwanted light escapes from one property into adjacent properties.” This can refer to bright porch lights kept on through the night in suburban areas or flickering neon lights from storefronts in urban areas.
Over-illumination is another type of light pollution, referring to “excessive light where it isn’t needed.” Over-illumination may refer to floodlights in parking lots or fluorescent bulbs kept on all night in empty office buildings. Light clutter -- very much what it sounds like -- refers to “the redundant clusters of lighting found in many urban centers” -- from large marquees to flashy billboards. The last type -- called “sky glow” -- refers to “the collective light pollution found over big cities,” which can easily be seen from space.
Economic Costs of Light Pollution
People across the globe often assume that lit areas are safer -- better protecting residents and workers from crime or injury during a disaster. Appropriate, directed light does indeed keep people safe when walking along a path at night or passing through a parking lot in the early morning. However -- notes the JMU article -- many of the lights we leave on to keep us safe at night actually “produce so much glare that you have poor visibility” instead. Artificial lights can also confuse wildlife, disorienting potentially dangerous animals and leading them into cities and suburbs. Furthermore, light pollution costs the economy billions each year in addition to harming human health and that of the environment. The IDA found that “at least 30 percent of all outdoor lighting in the U.S. alone is wasted, mostly by lights that aren’t shielded.” Each year, this “adds up to $3.3 billion [expended] and the release of 21 million tons of carbon.” To combat excessive light pollution, impacts on the environment and countless wasted dollars, the IDA and other organizations advocate for smart lighting solutions. These include using energy-efficient light bulbs, timers and shields -- among many other options.
How Light Pollution Impacts Human Health
From the United States to Israel to South Korea, people all over the world are suffering from the ill effects of artificial light pollution. Their lives have been altered in ways both big and small -- including increased rates of depression, higher risk of breast cancer and reduced productivity from disrupted sleep. Forced continuous exposure to artificial light affects sleep quality, hormone production and the preservation of our circadian rhythm -- all of which can impact our daily lives and our live-long health. Blocking the release of melatonin might be one of the most insidious effects of light pollution -- particularly in women. Follow below to learn more about the varied -- and incredibly dangerous -- costs of light pollution to human health.
Interfering with Release of Melatonin Linked to Breast Cancer, Failed Modulation of Circadian Cycles and More
Artificial light -- particularly blue light -- can block or delay release of the hormone melatonin throughout the body. Melatonin The National Center for Complementary and Integrative Health -- associated with the NIH -- explains the importance of this hormone in their brief “Melatonin: What You Need To Know.” According to the brief, melatonin “is a hormone that your brain produces in response to darkness” to help “with the timing of your circadian rhythms (24-hour internal clock) and with sleep.” Combined, the release of melatonin and the body’s reactions to the rising and setting of the sun -- e.g. natural light cycles -- preserve sleep quality and bodily health. Some people choose to take melatonin as a supplement in order to “help with certain conditions, such as jet lag, delayed sleep-wake phase disorder, some sleep disorders in children, and anxiety before and after surgery.” However, the release of melatonin remains an important function for all people. Not only does melatonin aid sleep regularity, but it also impacts other areas of bodily health.
Disruption of the Circadian Cycle
In his paper “Missing the Dark: Health Effects of Light Pollution” for the Journal of Environmental Health Perspectives, Ron Chepesiuk describes consequences of disrupting the circadian cycle in humans. He writes that the circadian clock -- our “24-hour day/night cycle” -- affects “physiological processes” in humans, animals and plants. It impacts “brain wave patterns, hormone production, cell regulation and other biological activities.” Impacting these processes by disrupting the circadian cycle can have dire health effects -- both mental and physical -- on the brain and body. Chepesiuk writes that disruptions of the circadian cycle have been linked to “several medical disorders in humans, including depression, insomnia, cardiovascular disease, and cancer.” Quoting Paolo Sassone-Corsi -- who at the time served as chairman of the Pharmacology Department at UCI -- Chepesiuk writes that “‘studies show that the circadian cycle controls from ten to fifteen percent of our genes.’” Because of this -- Sassone-Corsi explains -- “‘the disruption of the circadian cycle can cause a lot of health problems.’”
In their paper “Health implications of disrupted circadian rhythms and the potential for daylight as therapy,” Dr. Jason Brainard, M.D and his colleagues tied disruption of the circadian cycle to behavioral disorders, acute illness and disease. They note that new evidence that has come to light in recent years has exposed “explicit connections between disrupted circadian rhythms and numerous clinical disorders.” Among those listed by Chepesiuk, these include “obesity, premature aging, diabetes, cardiac arrhythmias, immune deficiencies [and] hypertension.” In fact, “a disrupted circadian rhythm and poor-quality sleep are associated with insulin resistance, high glucose levels and elevated blood pressures.” These issues are of particular concern, as they already affect so many people worldwide and have severe consequences for both quality and length of life. A 2018 study from the American Heart Association found that “an estimated 103 million U.S. adults have high blood pressure.” From 2005 to 2015, the death rate from high blood pressure “increased by nearly 11 percent in the United States.” As light pollution explodes across the nation -- and globally -- more people will be at increased risk of these potentially deadly medical issues.
Insufficient or Irregular Melatonin Release and Breast Cancer
A number of recent studies have explored the relationship between melatonin, estrogen and breast cancer. According to Ron Chepesiuk in his paper “Missing the Dark: Health Effects of Light Pollution” for the Journal of Environmental Health Perspectives, “studies suggest that decreasing nocturnal melatonin production levels increases an individual’s risk of developing cancer.” This is because melatonin influences hormone production -- particularly that of estrogen. One of the biological activities triggered by melatonin is limiting the production of estrogen at night, Chepesiuk explains. High levels of estrogen in the body are believed by doctors and researchers to greatly increase one’s risk of developing breast cancer.
Reducing the production of melatonin through prolonged wakefulness due to exposure to artificial light at night encourages the maintenance of high levels of estrogen production. In his paper, Chepesiuk references a 2008 study that recorded the rates of breast cancer of women in areas with intense light pollution and with minimal light pollution. The study found that “women living in neighborhoods where it was bright enough to read a book outside at midnight had a 73% higher risk of developing breast cancer than those residing in areas with the least outdoor artificial lights.”
How Much Artificial Light is Too Much at Night?
Unfortunately, even limited exposure to artificial lights can have serious consequences for mental and physical health -- including hormone production and sleep quality. Exposure to blue light in the evening after the sun has set is even more harmful than exposure to other wavelengths. A Harvard Health Letter from May 2012 -- updated in June of 2020 -- details why blue light exposure has a more significant impact on our health than that of red or green light. The letter notes that compared to other colors of light, blue light suppresses the secretion of melatonin more powerfully and for longer periods of time. Referencing prior light exposure experiments conducted by Harvard researchers, the letter explains that “blue light suppresses melatonin for about twice as long as the green light and shifted circadian rhythms by twice as much (3 hours vs. 1.5 hours).” Unfortunately, “even a dim light can interfere with a person’s circadian rhythm and melatonin secretion.” Quoting Harvard sleep researcher Stephen Lockley, the brief notes that “a mere eight lux...has an effect.” For reference, light bulbs from table lamps, night lights and other indoor lighting typically range from 500 to 850 lumens where one lux is equal to one lumen per square meter.
Even Dimmed Devices Impact Sleep Quality and Circadian Cycle
In their 2015 paper “Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness” researchers Anne-Marie Chang, Daniel Aeschbach, Jeanne F. Duffy and Charles A. Czeisler studied the impact of dimmed screens on sleep. E-readers and tablets typically release between 300 and 600 lux -- a light level considered dim during the day but too high at night. Chang, Aeschbach, Duffy and Czeisler found that using such devices before sleep “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.” Looking at a tablet, phone or other blue-light-emitting device just before bedtime “increases alertness...which may lead users to delay bedtime at home.” In conclusion, the researchers 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.”
How Many Households Are Impacted by Light Pollution?
In the BBC Future article “What rising light pollution means for our health,” Richard G. 'Bugs' Stevens from the University of Connecticut notes that light pollution has not only obscured the night sky from billions of people but has also altered their physiology. Stevens writes that “thanks to sky glow, the Milky Way is no longer visible to one-third of humanity, with the most heavily industrialised regions suffering the greatest loss.” In fact, at least 60% of Europeans and 80% of people in North America “can no longer see the Milky Way at night” due to excessive light pollution. Inhabitants of and around large cities where light pollution leaks into neighboring sparsely populated regions are most at risk, writes Stevens. In these areas, “the local light levels outside on the street are at times enough to prevent or delay transition to our normal night-time physiology which should begin at about sunset.” Another BBC News article composed by science correspondent Rebecca Morelle revealed that “more than 80% of the world's population lives under light-polluted skies,” putting them at risk of all the disorders, illnesses and ill effects associated with disrupted circadian cycles.
5 Ways to Limit Light Pollution in Your Neighborhood
#1 Fit Lights with Low-Glare Bulbs Approved by the International Dark Sky Association
Reducing glare in outdoor light fixtures -- whether porch lights or path lights -- limits light pollution without compromising on safety. Many porch lights direct light outward rather than downward, flooding the street and blinding passersby at the same time. Glaring, outward-facing light does little to improve safety and can actually be disorienting for neighbors in their homes, people walking by and drivers. A recent CoreGlow post notes that “the International Dark Sky Association certifies dark sky friendly light fixtures that meet their rigorous guidelines.” Lights stamped with the IDA’s Fixture Seal of Approval “minimize glare, reduce light trespass, and don’t pollute the night sky.”
#2 Talk to Neighbors About Their Unshielded Lights
As mentioned above, unshielded lights not only drench the owner’s driveway with useless, undirected light, but they also pollute neighboring homes and businesses. The IDA brief “My Neighbor’s Lighting” offers advice for dealing with neighbors who needlessly pollute the community with unshielded lighting referred to as “light trespassing.” The International Dark Sky Association recommends a series of “practical actions” for dealing with such situations, reminding homeowners that “your neighbor may not even realize that their unshielded lighting is shining on your property, wasting energy, money and creating a safety hazard.” The association suggests offering “alternatives to their current fixture [and] offering to help get this done.” Explain that unshielded light is polluting your property and affecting your quality of life without becoming combative.
#3 Equip Outdoor Lights with Timers or Motion Sensors
Equipping outdoor lights with timers or motion sensors will not only save money on energy output and reduce a household’s carbon footprint but will also reduce artificial lighting pollution. In the article “5 Ways You Can Reduce Light Pollution” for TreeHugger, Chris Baskind writes that “lighting on demand trumps a manual switch or timer.” Outfitting outdoor lights with “motion sensitive switches will light up porches and walkways when you need to move around after dark” without blinding neighbors.
#4 Advocate for Shielded Street Lights in Your Community
The Conserve Energy Future article “21 Impressive Ways to Reduce Light Pollution” first recommends educating oneself about the dangers and prevalence of light pollution before speaking to community leaders. The brief notes that “having knowledge about the sources and effects of light pollution can significantly aid in dealing with the problem.” Equipping oneself and one’s community with “extensive awareness” is the first step in reducing pollution citywide because “most people don’t even know about artificial lighting pollution.” After educating the community, encourage businesses, builders, government leaders and homeowners to opt for dimly lit, shielded street lights.
Explain that dim lighting is more than enough for cars to drive safely and people to navigate at night. Brighter light can actually “cause glare, which may blind oncoming drivers and even interfere with wildlife habitats by altering their natural cycles and operations.” Also encourage businesses to turn off office lights at night when buildings are empty and homeowners to switch to motion sensitive lights. To help your case, reference studies revealing that continuous nighttime lighting might not deter crime. According to NPR’s Zhai Yun Tan in the article “Should You Leave Your Lights On At Night? It Depends,” FBI statistics have shown that “most residential crime actually occurs in daylight.”
#5 Turn Off Indoor Lights When Unneeded
In the article “5 Ways You Can Reduce Light Pollution” for TreeHugger, Chris Baskind writes that “the cheapest, most obvious and most effective way to reduce light pollution is to start turning things off.”