If you have ever gone on a trip to the countryside and paid attention to the night sky, you might have noticed it to be different than the one in urban areas like São Paulo. Although the visibility of the stars can be affected by factors such as air quality (Hennig), another determiner of whether you will be able to capture that nice moment with millions of tiny dots is the level of light pollution in the area.
Humans pollute the earth in many ways, through industrial activities, waste management, agricultural processes, and even generating electricity (“16 Most Dangerous Natural and Man-made Sources of Air Pollution - Airly WP | Air Quality Tracker Airly”). Interestingly, many are unaware of light pollution, a type caused by the mass distribution of light bulbs globally, which led to the excessive use of artificial light during the night (Cobb), especially within urban areas that accommodate higher numbers of people. "How may this disrupt anything?" one may ask. The answer lies in the several prominent yet seemingly unrelated consequences of such pollution; its environmental influence, health impacts, and how it affects the visibility of cosmic elements. To help minimize these consequences, investigating the origins of the issue and viable solutions are necessary.
According to the International Dark-Sky Association, whose purpose is to preserve the night sky for current and future generations, constituents of light pollution include clutter, light trespass, skyglow, and glare. A Lot of the lighting used outdoors ends up being wasted and spread into the sky, due to the exaggeration of brightness, inefficiency, improper shielding or direction of the light, and unnecessary locations. Qualitatively measuring light pollution can be done by almost any individual by simply looking up to the sky over a period of time since approximately 80% of the global population lives within areas covered by skyglow (Gocova). However, a more accurate way to measure it is by using a Sky Quality Meter, a device that can measure the night sky's brightness in magnitudes per square arcsecond.
High levels of sky brightness at night may have adverse effects on your circadian rhythm (Tracy and Wu). That is because of how light affects the suprachiasmatic nucleus (SCN), a part of the hypothalamus region in your brain that plays an important role in the time regulation of eating and sleeping patterns. Given light is one of the main external indicators for internal clock modulation, the SCN is greatly sensitive to it. The SCN begins signaling a pathway to reduce Melatonin once we are exposed to artificial light at night, which leads to weariness during the day and difficulty sleeping at night. Research suggests disrupted sleep cycles and low melatonin can also lead to higher chances of cancer, given the thought that they might be an obstacle to genes that suppress cancer. An experiment in which Richard Stevens, a cancer epidemiologist, and professor at the University of Connecticut, took part in an investigation of the link between rates of breast cancer and of light pollution (collected through satellite images) in communities of Israel (Chepesiuk). Results showed a significant link between both factors even with variables such as affluence, population density, and air pollution controlled. They suggested the women who lived in neighborhoods where the outdoor light was enough to read a book had a 73% higher chance of developing breast cancer.
Apart from light pollution negatively impacting human health, it can also be highly damaging for different animal species. Altered levels of lighting at night are extremely dangerous for migratory birds because they can change their behaviors, communication, and patterns of migration which cause disorientation and collisions that lead to their death every year (Fryš). Some seabirds are also attracted by light and may be consumed by predators out of their natural food chain that reside in the city. Light pollution also affects hatchling sea turtles (Nathanson) because they guide themselves near the brightest horizon once they are out of the egg since naturally, that would be the waters. Once bright lights are placed, for instance, on a sidewalk near the beach dead baby turtles can be found in that same direction. Lastly, it also affects plants because it can cause alterations in their photoperiodism.
An article published by the "Science Advances" journal of the American Academy for the Advancement of Science suggests that more than one in every three humans can only access an obscured view of the milky way during the nighttime. This impedes the process of astrophotography in large urban settlements, and can also be prejudicial to astronomers. The component of light pollution that interrupts the visibility of celestial objects is skyglow, which is the result of poorly directed light that leaks into the sky and that the solid/liquid particles in the atmosphere reflect. Astronomers have to travel to distant observatories in regions with lower levels of light in the sky for a decent view of our galaxy, which can reduce the accessibility of the study. Apart from that, it is simply appalling that if urbanization and development lead to increasing levels of light pollution, large portions of our future generations might never be able to see the stars.
Even though there is not much awareness of this type of pollution, its effects could be minimized through street light design. That is to be done in three steps, shielding the light, using warmer colors, and dimming it (Montjoy). Using warmer colors rather than blue lights reduces the impact on the circadian rhythm and disperses less light even though they have similar energy efficiency and prices as traditional blue lights. Ensuring light levels are uniform and moderated through time depending on use is also a more sustainable alternative. Sources suggest that dimming lights outdoors by 25% would not reduce any visibility. Lastly, shielding lights and projecting them downwards prevents any wastage and reduces skyglow. Many designers have come up with street lamp designs in light of the issue.
To conclude, the hope for the future is that governments endorse policies to ensure the use of dark-sky friendly outdoor lighting. In case that does not occur, the next time you visit a place that is completely dark at night, take a good look at the stars, because the brighter our nights become, the less you'll be able to see them.
Chepesiuk, Ron. “Missing the Dark: Health Effects of Light Pollution.” NCBI, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2627884/. Accessed 17 June 2022.
Cobb, Jodi. “Light Pollution.” National Geographic Society, 2 June 2022, https://education.nationalgeographic.org/resource/light-pollution. Accessed 17 June 2022.
David, Byrce. “5 Appalling Facts about Light Pollution.” International Dark-Sky Association, 29 July 2016, https://www.darksky.org/5-appalling-facts-about-light-pollution/. Accessed 17 June 2022.
Fryš, Jakub. “World Migratory Bird Day illuminates the dark side of light pollution.” UN News, 13 May 2022, https://news.un.org/en/story/2022/05/1118262. Accessed 17 June 2022.
Gocova, Anezka. “Light Pollution.” International Dark-Sky Association, https://www.darksky.org/light-pollution/. Accessed 17 June 2022.
Hennig, Amee. “How Light Pollution Affects the Stars: Magnitude Readers.” astroEDU, https://astroedu.iau.org/en/activities/how-light-pollution-affects-the-stars-magnitude-readers/. Accessed 17 June 2022.
Montjoy, Valeria. “How to Reduce Light Pollution With Street Light Design?” ArchDaily, 24 February 2022, https://www.archdaily.com/977131/how-to-reduce-light-pollution-with-street-light-design. Accessed 17 June 2022.
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Rehagen, Tony. “There's too much artificial light at night to see stars. That's a problem.” The Boston Globe, 20 September 2019, https://www.bostonglobe.com/ideas/2019/09/20/goodnight-night-sky-and-everything-else-losing-our-over-illuminated-world/Eex5BuZ5dVhfDslpPYrC1L/story.html?p1=Article_Inline_Text_Link. Accessed 17 June 2022.
“16 Most Dangerous Natural and Man-made Sources of Air Pollution - Airly WP | Air Quality Tracker Airly.” Airly, https://airly.org/en/16-most-dangerous-natural-and-man-made-sources-of-air-pollution/. Accessed 17 June 2022.
Tracy, Samantha, and Wei Wu. “I Can't Sleep… Can you turn off the lights? - Science in the News.” Science In The News, Harvard University, 13 October 2020, https://sitn.hms.harvard.edu/flash/2020/i-cant-sleep-can-you-turn-off-the-lights/. Accessed 17 June 2022.