The Dark Side of Light

Light emission in Europe. [1]

The world that we live in today is a world of light. Light is used everywhere, by everybody, and for everything. There is no escaping it. Where ever you go, there is always a glow of light shining from somewhere. Prior to the modern world, the Earth and life on it used to be controlled by the natural cycle of day and night, light and dark. “Someone once said that the 24-hour … rhythm evolved because the Earth revolved”[2]. The cycle is a universal characteristic that is shared by all animals, insects and even bacteria[3]. But, as in so many other instances, we humans have managed to manipulate and interrupt nature, and with the help of technology take over control of it. In order to take better advantage of night-time and to use it for other purposes, we have filled darkness with artificial light. But this kind of disregard for nature does not come without consequences.

For over a century the amount of artificial light and light sources has kept increasing while banishing darkness and natural night almost completely from the modern world. In fact, “now most of humanity lives under intersecting domes of reflected, refracted light, of scattering rays from overlit cities and suburbs, from light-flooded highways and factories. Nearly all of nighttime Europe is a nebula of light, as is most of the United States and all of Japan”[4]. Most often the increase of the amount of artificial light and new innovations are seen as positive developments that allow us to work and socialize after sunset. But it also means that light is present everywhere, even to the extent that we are no longer able to have complete darkness. Most people don’t think that something as simple as light could possibly do any harm. What does it matter if you work at night, or sleep with a light on? Who cares if cities create light pollution? The more light the better, right? The answer, however, is that it does matter – probably more than you would even think.

For billions of years, life on Earth has evolved and lived in a relationship with sunlight. In that time light has become “a powerful biological force”[5] that has strong effects on many species. Even though we often like to think of ourselves as a superior species, different from other animals, also the humans race needs darkness in their lives. Living in the excessive light jungle that we have created has separated us from the day and night cycle that evolution has meant for us. It also affects many creatures in the animal kingdom in many different ways. The results of widespread use of artificial light may actually be even more easily seen in animals because they are less adaptable than us.

The presence of artificial light alters the habitats where animals live, hunt, breed, nest, and sleep, which has various negative effects on the animals. Distraction and confusion seem to be the two main reasons that lead to the unfortunate results. Most of the big cities around the world are by sea coasts and are illuminated at night which, as mentioned in a book about sea turtles in America[6], presents a problem for sea turtles. Adult sea turtles prefer to make a nest and lay their eggs on a dark beach but bright lights often frighten them back into the sea making nesting more difficult for them. Even if the adults succeed to lay their eggs correctly, the turtles’ calamity does not end there. Unlike their parents, the hatchlings are drawn towards light. The natural gleam of the horizon is supposed to guide the hatchlings into the water but the poor baby turtles are disorientated by the bright lights of coastal cities and often start crawling into the completely wrong direction where they are more likely to be eaten by predators or hit by cars. According to National Geographic, in Florida alone, hatchling losses number in the hundreds of thousands every year[7]. The habit and biological mechanism that the turtles have been following for millions of years has been hijacked by the appearance of artificial light and the loss of natural darkness.

Animals can fall into great danger also because their inner clock, called circadian rhythm, gets confused as a result of increased levels of light in nocturnal hours. For example, according to a study, mortality among squirrels who were up and about at night was twice as high compared to squirrels whose day and night rhythm was in order. The reason is that the squirrels who were not safely sleeping in their burrows were more vulnerable to nocturnal predators[8]. Similar links have also been seen in chipmunk populations as well as in the behaviour of rodents, opossums, and badgers in areas with high light pollution[9].

Also many species of birds are strongly affected by artificial lights. Birds that fly around at night may easily get fixated on bright lights, and as a result of it, crash into illuminated buildings and skyscrapers[10]. Especially young birds migrating for the first time are in an elevated risk because of their lack of experience. Scientists have also found that diurnal birds tend to extend their daily active period into the night as a result from the light levels that artificial light prolongs. Some songbirds also start singing at odd times of the day for the same reason. Singing at abnormal hours again can affect their breeding patterns[11]. Longer days also allow more time and opportunities for eating which makes the birds put on fat quicker. Because of this, when Bewick’s swans in the spring gained weight quicker than usual, they also were ready to move back to the North earlier[12]. The risk in this kind of situations is that the weather back home might still be too cold for them or the conditions are not suitable for nesting yet. All these are very alarming examples of the risks and whirlpools that the lack of natural amount of darkness puts birds into. And the reason why they are so fatal is that evolution has not prepared the birds for those.

Another example of negative effects in the nature is affiliated with moths. The consequences caused by artificial light, however, arise outside of the moth species. Researchers in Oxfordshire have found “that there were about half the number of the insects at ground level in lit areas compared to unlit areas, while the numbers at the height of street lights doubled when they were switched on”[13]. For some unknown reason moths are drawn to light which is distracting them from pollination. According to the researchers, this change caused by light pollution can “contribute to catastrophic declines”[14] in plant populations pollinated by moths. It is quite scary to think that our use of artificial light can indirectly affect even the whole ecosystem by setting off a domino effect. Although, it does not come as a surprise considering the amount of street lights and light pollution there are nowadays and how everything in nature is linked together.

We humans are definitely not free of the downsides of the lack of darkness caused by artificial light either. We may not get eaten by predators or lose track of where we are supposed to go, but we too are affected by the bright lights that have turned the Earth into a shimmering orb. Like many other creatures, we also need darkness. It plays a crucial part in our biological well-being and the regulation of our inner clock. The natural rhythms of day and night and sleep and waking are rooted so deep in us that “altering them is like altering gravity”[15]. Regardless, during the past century, we have put ourselves thorough “an open-ended experiment”[16] by shortening the night and extending the day. The physiological and behavioural symptoms that we suffer from are only now starting to become clear to us, and they can be very surprising since we would not think that they can possibly stem from light.

The basis of all the havoc that light at night-time plays on us is the bypass of the natural circadian rhythm. In a natural environment where there is no artificial light, people’s bodies start to synthesize a hormone called melatonin when the day starts to come to an end and it’s getting darker. And when the sun rises again in the morning, the synthesis of melatonin ends and the hormone gradually decreases. The different levels of melatonin in different times of the day tell our bodies when it is time to go to sleep and when it is time to wake up and be active.[17] When we add artificial light to the equation, this natural rhythm and the regular oscillation of melatonin is disrupted. Lack of melatonin causes troubles with sleep as well as many more and less serious diseases.

shifts in color during the day regulate our physiology
Without artificial light the circadian cycle and melatonin levels in our bodies
are regulated by the natural light levels at different times of the day.[18]

Negative effects on sleep are probably the most straightforward and understandable consequences from artificial light. One incident where this has been recorded is a study conducted by American and Argentinian researchers which shows that artificial light triggers a notable reduction in human sleep[19]. They studied two Argentinian communities: one where people had free access to artificial light and another one where people relied purely on natural light. The community living with artificial light slept from 40 to 60 minutes less per night than the community without light. Those people went to bed later but woke up about the same time as the others. As the study was done on hunter-gatherer communities, the researchers have noted that all the effects they found “are probably an underestimation of what we would see in highly industrialized societies where our access to electricity has tremendously disrupted our sleep”. We can only imagine how much worse the situation must be, for example, in the big densely populated European cities that are full of light 24 hours a day and where we are completely isolated from the natural period of darkness! No wonder that people in urban environments suffer from sleepiness when they must get up for work early in the morning.

During the past decade in the industrialized world, we have also gotten used to staring at TV screens, computers and smart phones all the time which all are backlit with artificial light. These new devices just add to the amount of light that we are exposed to in the evenings and at night and consequently makes us sleep less by suppressing the production of melatonin. Screens also use lights of blue wavelengths which suppress melatonin twice as powerfully as any other kind of light[20]. That is why light from screens is especially bad for us. And because regular exposure to light outside of the natural circadian rhythm may cause sleepiness during day and sleeplessness at night, we are advised to avoid watching TV and using computers before bedtime and at night-time.

However, avoiding artificial light at night is not possible for everybody. People are not meant to work at night and sleep during the day but the composition of the modern industrialized societies forces some people to do so. We need the police, firemen, and doctors to be available also at night, and we want bars, restaurants, and shops to be open, as well as transport to run all through the night. The people working in these sorts of professions suffer from the lack of darkness the most. They can pretty much kiss goodbye to even dreaming about the biological inner clock and normal melatonin levels. Considering all the negative effects of artificial light already mentioned above, it hardly is a surprise that this kind of extreme lack of darkness and a complete disregard for circadian rhythm is very bad for people. The extent of the health risks became clear when researchers kept mice under artificial light for 6 months. By the end when the mice were examined, they were found to be “suffering from muscle loss and early signs of osteoporosis”. Also, their immune system was in a state similar to what it would be if it was reacting to an infection.[21]

People might question the applicability of the knowledge gathered from the mice to humans, but similar symptoms have been found also in nurses who work night-shifts. In a publication by the European Commission, they mention a possible link between nurses’ hip and wrist fractures and duration of their night shift-work. However, only one study has been made on nurses, and other studies have been inconsistent in their results.[22]

Even if scientists still are unsure about the association between osteoporosis and the lack of darkness, there are many other studies that have firm evidence of other serious consequences of night shifts. Since shift-workers are constantly fighting against the evolutionary physiology that we have, “shift work disrupts sleep and makes people tired. It is bad for their health and makes them more likely to have accidents”[23]. They also have trouble falling asleep when their shift is over, they sleep less and feel less alert when they are awake. In addition to this, they suffer more from stress, depression and emotional problems and drink more alcohol. Even more drastic are the results that show a strong connection to increased risk of cancer and cardiovascular disease. Just how much more likely night shift-workers are to develop a heart disease became apparent in a study that followed their health over many years. After 11 years of shift work their risk had more than doubled and after 15 years it had almost tripled. According to the researchers’ conclusion, after 20 years many of them had already developed a heart disease and died.[24]

It sounds unbelievable how simply working at night can cause all those things. But when a person’s body is in such asynchrony for a prolonged time and exposed to light in the wrong time of the day causing abnormal melatonin levels, it is not really a surprise that our bodies react to it. Even though night workers may be an extreme representation of what our world of light can do to us, it does show the possible negative consequences it can have for all of us. And as melatonin has been found to work as “a protective agent against ‘wear and tear’ in several tissues”[25], it is no wonder that by suppressing its production our style of living in a vast sea of light can predispose us to all kinds of illnesses and afflictions.

human factors in lighting p.101
Melatonin concentrations at different times from 10 pm to 5 pm.
The control group was not exposed to light, but the other groups where
exposed to light (either 200, 400, or 600 lx) between 12 am and 3 am.[26]

Heightened risk of breast cancer is a consequence from disrupted circadian rhythm that has been detected in people whether they do night shifts or not. In a study made in the USA, researchers found that women who for many years often worked at night were up to 60 percent more likely to get breast cancer[27]. In addition to night shifts, other possible situations where people may suffer from lack of darkness are: sleeping in a lit bedroom, and getting light pollution into your house from outside in highly lit areas, like cities. These have been noticed to increase the risk of breast cancer, whereas people who live in the arctic circle where withers are long and the daily amount of light is small have a decreased risk of it[28]. This piece of scientific knowledge is interesting because it shows that we don’t only need natural darkness in our lives but it can actually make us better protected against some diseases.

Light pollution and sleeping in a bedroom where light can get to can have another surprising effect on the human body. A study made in London by the Institute of Cancer Research reveals a link between too much artificial light at night and obesity. When measured, women who slept in a room too bright had higher body mass index, waist-to-hip ratio and waist circumference. This doesn’t even require the bedroom light to be switched on, just light from alarm clocks, TV, or light pollution from the streets can be enough.[29] Unlike you would think, closing your eyes or falling asleep does not necessarily shield you from the negative effects – the unwanted light stays with you all through the night. This was demonstrated by researchers at Cornell University when they shined bright light to the back of the test subject’s knees and noticed that it affected their circadian rhythm. They explained the discovery with the possibility that “the bright light affects blood in capillaries close to the surface of the skin, stimulating the release of a substance such us nitric oxide” which would then affect the brain.[30] Another link to obesity in humans is the same what the Bewick’s swans experienced in the first part of this essay. They put on weight quicker in areas where the day was extended by the use of artificial lights. With artificial light and shortened nights, we too have more time for eating. Also, if people still eat after the natural dusk when the metabolic processes have already slowed down[31] the energy must be stored in the body due to the inability to process and use it. This will in a long run result in extra kilos around your hips. The situation gets even worse when we take into account the research outcomes which show that shifts in circadian rhythm can also lower the levels of a hormone called leptin in people. Leptin’s job is to leave us feeling full after a meal.[32] If the hormone level is down, we won’t feel full but instead may just keep eating more.

Undoubtedly there are even more downsides of artificial light to be discussed, but even the ones pointed out above are enough to make it apparent how important darkness really is to us, as well as, to the other creatures that we share the Earth with. The world is trapped in the unstoppable shine of lights that we have created. The excessive artificial light has pushed the natural forces and the evolution into a corner and the results of it are now popping up everywhere around us in new scientific studies. Through changes in environments and inner body clocks, animals find themselves in new kinds of dangers and people are less healthy than before the darkness was filled with continuous light. Even though artificial light is one of the main building blocks of the modern societies, and to an extent the very reason that allows us to maintain the free lifestyle that is not restricted by night-time, the negative effects of it are just as powerful. In the future, we must pay more attention to the importance that darkness plays in the world and not let light dominate it too much. We simply can’t afford to sacrifice ourselves and the rest of the Earth’s creatures to the its negative effects – the “dark side of light”.

 

Footnotes

 

[1] Brandi, Ulrike & Geissmar-Brandi, Christoph, Light for Cities : Lighting Design for Urban Spaces. A Handbook, (Basel, Birkhäuser, 2007), p. 47

[2] Martin, Paul, Counting Sheep : the science and pleasures of sleep and dreams, (Great Britain, Flamingo, 2003), p. 114-115

[3] Boyce, Peter R. Human Factors in Lighting, (London, Taylor & Francis, 2003), p. 95

[4] Klinkenborg, Verlyn, National Geographic 14/2008: Our Vanishing Night, (National Geographic Society, 2008), p. 88-90

[5] Klinkenborg, Verlyn, National Geographic 14/2008: Our Vanishing Night, (National Geographic Society, 2008), p. 90

[6] Ruckdeschel, Carol & SHOOP, C. Robert, Sea Turtles of the Atlantic and Gulf Coasts of the United States, (Athens, Georgia, The University of Georgia Press, 2006), p. 26

[7] Klinkenborg, Verlyn, National Geographic 14/2008: Our Vanishing Night, (National Geographic Society, 2008), p. 90

[8] Martin, Paul, Counting Sheep : the science and pleasures of sleep and dreams, (Great Britain, Flamingo, 2003), p. 115-116

[9] Klinkenborg, Verlyn, National Geographic 14/2008: Our Vanishing Night, (National Geographic Society, 2008), p. 90

[10] Murgui, Enrique & Hedblom, Marcus (Eds.), Ecology and Conservation of Birds in Urban Environments, (Springer International Publishing, 2017), p. 8

[11] Murgui, Enrique & Hedblom, Marcus (Eds.), Ecology and Conservation of Birds in Urban Environments, (Springer International Publishing, 2017), p. 255

[12] Kear, Janet (Ed.), Ducks, Geese and Swans: General chapters, species accounts (Anhima to Salvadorina), (England, Oxford University Press, 2005), p. 127

[13] http://www.independent.co.uk/news/science/moths-street-lights-pollination-crops-plants-a7059496.html

[14] http://www.independent.co.uk/news/science/moths-street-lights-pollination-crops-plants-a7059496.html

[15] Klinkenborg, Verlyn, National Geographic 14/2008: Our Vanishing Night, (National Geographic Society, 2008), p. 91

[16] Klinkenborg, Verlyn, National Geographic 14/2008: Our Vanishing Night, (National Geographic Society, 2008), p. 91

[17] Boyce, Peter R. Human Factors in Lighting, (London, Taylor & Francis, 2003), p. 100-101

[18] http://www.metropolismag.com/interiors/healthcare-interiors/why-light-matters-designing-with-circadian-health-in-mind/

[19] http://www.independent.co.uk/life-style/gadgets-and-tech/news/access-to-electricity-and-artificial-light-triggers-a-reduction-in-sleep-study-says-10334820.html

[20] http://www.health.harvard.edu/staying-healthy/blue-light-has-a-dark-side

[21] http://www.independent.co.uk/news/science/artificial-light-street-lights-sleep-frail-muscles-bones-osteoporosis-a7136761.html

[22] SCENIHR (Scientific Committee on Emerging and Newly Identified Health Risks) of the European Commission, Health Effects of Artificial Light, (European Commission, 2012), p. 56

[23] Martin, Paul, Counting Sheep : the science and pleasures of sleep and dreams, (Great Britain, Flamingo, 2003), p. 163

[24] Martin, Paul, Counting Sheep : the science and pleasures of sleep and dreams, (Great Britain, Flamingo, 2003), p. 163-164

[25] SCENIHR (Scientific Committee on Emerging and Newly Identified Health Risks) of the European Commission, Health Effects of Artificial Light, (European Commission, 2012), p. 54

[26] Boyce, Peter R. Human Factors in Lighting, (London, Taylor & Francis, 2003), p. 101

[27] Martin, Paul, Counting Sheep : the science and pleasures of sleep and dreams, (Great Britain, Flamingo, 2003), p. 164

[28] SCENIHR (Scientific Committee on Emerging and Newly Identified Health Risks) of the European Commission, Health Effects of Artificial Light, (European Commission, 2012), p. 56

[29] http://www.bbc.co.uk/news/health-27617615

[30] Martin, Paul, Counting Sheep : the science and pleasures of sleep and dreams, (Great Britain, Flamingo, 2003), p. 117

[31] http://www.independent.co.uk/life-style/health-and-families/health-news/artificial-lights-near-homes-linked-to-obesity-in-new-study-a6925701.html

[32] http://www.health.harvard.edu/staying-healthy/blue-light-has-a-dark-side

 

Bibliography

Books

BOYCE, Peter R. Human Factors in Lighting, (London, Taylor & Francis, 2003)

BRANDI, Ulrike & GEISSMAR-BRANDI, Christoph, Light for Cities : Lighting Design for Urban Spaces. A Handbook, (Basel, Birkhäuser, 2007)

KEAR, Janet, Ducks, Geese and Swans: General chapters, species accounts (Anhima to Salvadorina), (England, Oxford University Press, 2005)

KLINKENBORG, Verlyn, National Geographic 14/2008: Our Vanishing Night, (National Geographic Society, 2008)

MARTIN, Paul, Counting Sheep : the science and pleasures of sleep and dreams, (Great Britain, Flamingo, 2003)

MURGUI, Enrique & HEDBLOM, Marcus (Eds.), Ecology and Conservation of Birds in Urban Environments, (Springer International Publishing, 2017)

RUCKDESCHEL, Carol & SHOOP, C. Robert, Sea Turtles of the Atlantic and Gulf Coasts of the United States, (Athens, Georgia, The University of Georgia Press, 2006)

SCENIHR (Scientific Committee on Emerging and Newly Identified Health Risks) of the European Commission, Health Effects of Artificial Light, (European Commission, 2012) http://ec.europa.eu/health/scientific_committees/emerging/docs/scenihr_o_035.pdf

 

Websites

BBC http://www.bbc.co.uk/news/health-27617615 (first accessed 30.03.2017)

HARVARD HEALTH PUBLICATIONS http://www.health.harvard.edu/staying-healthy/blue-light-has-a-dark-side (first accessed 29.03.2017)

INDEPENDENT http://www.independent.co.uk/news/science/moths-street-lights-pollination-crops-plants-a7059496.html (first accessed 27.03.2017)

INDEPENDENT http://www.independent.co.uk/life-style/gadgets-and-tech/news/access-to-electricity-and-artificial-light-triggers-a-reduction-in-sleep-study-says-10334820.html (first accessed 28.03.2017)

INDEPENDENT http://www.independent.co.uk/news/science/artificial-light-street-lights-sleep-frail-muscles-bones-osteoporosis-a7136761.html (first accessed 29.03.2017)

INDEPENDENT http://www.independent.co.uk/life-style/health-and-families/health-news/artificial-lights-near-homes-linked-to-obesity-in-new-study-a6925701.html (first accessed 27.03.2017)

METROPOLIS http://www.metropolismag.com/interiors/healthcare-interiors/why-light-matters-designing-with-circadian-health-in-mind/ (first accessed 28.03.2017)

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