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Many people are not familiar with the term “light pollution”. A bit of extra light seems benign in comparison to, say, global warming. However, it is nothing to be camplacent about. It disrupts our endocrine systems and robs us of our sleep. In the long run, it makes us ill. In this article, we will take a hard look at light pollution. It affects the quality (and quantity) of the sleep we are getting.

What On Earth Is Light Pollution?

Electric lighting on a large scale arrived in the late 1800s, and since then it changed how we live. For the first time in history, we could push darkness back completely. We have more hours of bright light than ever before. It is not by chance that shift-based work also started roughly at the same time. Industries could then operate at any hour, thanks to safe and cost-effective illumination. Entertainment also reaped the benefits of electric lighting. Sports arenas could host games in the evenings, with the bonus of extra attendance.

As the human population expands, so does our light footprint. It seems we cannot resist brightly lighting up any place at night if we get half a chance.

I would ascribe this to the primitive notion that a brightly lit environment is a safe environment. Some parts of our endocrine system are still wired for a more primitive existence, where we would constantly be under physical threat from predators. Many predators are nocturnal and can see well in the dark, while human eyes do not do such a fine job. They can see us, but we cannot see them, which makes us slightly paranoid. This seems to be the core reason for light pollution: all these extra lights at night make us feel safer. With high levels of nasty contact crime in South Africa, people instinctively go for “perma-noon” – bright lighting mimicking mid-day at night – as a safety measure. Ironically, people forget that criminals also benefit from the brightly lit environment, giving them (the criminals) beautiful visibility without having to attract attention with a torch.

So when is it merely illumination, and when does it become pollution? The short answer is: if it is needless, unwanted or damaging, it is pollution.

Brightly lit stadiums can cause light pollution

Types Of Light Pollution

• Over-illumination

Illumination which exceeds the actual need, like an empty office building with all the lights going full blast right through the night, qualifies as overillumination. Since the late 1980s, architectural lighting has become very popular: huge floodlights shining onto a building from the outside, all night. Over-illumination has crept into our streets, complexes and even our nature resorts.

• Glare

When light travels horizontally, directly from the source onto our retinas, we experience glare. It has an irritating, dazzling effect, even when seen from a distance.

• Light trespass

As the term implies, it is unwanted light spilling over from elsewhere, lighting up spaces that would otherwise be dark. The bright light emitted by street lights is probably the most common form of light trespass we experience nightly. Neighbours who invest in “perma-noon” lighting systems also tend to trespass this way, often oblivious as to where else all that light is going.

• Sky glow

When humans in towns and cities keep enough lights burning at night, the cumulative effect is sky glow – the orange to grey glow in the sky that makes stars difficult to see. The effect is caused by refracted light, due to particles in the air from air pollution or water condensation.

The Adverse Effects of Light Pollution

• Messing With Nature

Light cycles govern a multitude of functions in nature. For example, some plants respond to the length of days and start flowering when days get longer or shorter. This phenomenon is called photoperiodism. When the natural light cycle is disrupted, these plants literally don’t know if they’re coming or going. Shining floodlights on these plants at night will keep them locked into one stage of their natural cycle, never to progress.

Light pollution negatively affects many animals, from nocturnal insects like moths to birds, bats, turtles and even frogs. It disrupts their lives in many ways, including interference with their breeding cycles or meddling with their migration patterns.

• Sleep Deprivation And -Disturbances

The light-dark cycle, also known as the circadian clock, governs our sleep patterns. It enables our bodies to feel sleepy or awake at the appropriate times, by regulating the secretion of melatonin. The darker it gets, the more melatonin is secreted so we can feel sleepy, and vice versa. Disruption of the circadian clock directly affects our sleeping patterns.

In a typical first-world city, the amount of light hitting our retinas at night is staggering if you add up all the types of light pollution. Our bodies interpret this as a longer-than-normal day and delay the secretion of melatonin. Which means that we struggle to fall asleep. If we’re lucky enough to fall asleep anyway, the glow from behind the curtains again reduces the secretion of melatonin, which makes it harder to stay asleep and also to fall into deep sleep.

Before using electric lighting to stretch our days, our sleep patterns were different. Instead of sleeping one entire “block” of eight hours, most of us slept in two sessions of roughly four hours each, with an awake (but restful) hour or two in between. In this version of the cycle, people were exposed to around twelve hours of darkness, whether they are asleep or not. In rural areas with less light pollution, this is often still possible. The unnatural length of our days, thanks to bright lighting, has caused us to feel sleepy later in the 24-hour cycle and resulted in meshing our two sessions of sleep into one long one.

light pollution is caused by all the unnecessary lights around town.

• Direct Health Risks

Apart from the dangers associated with sleep disturbances or -deprivation, disrupting the circadian clock with overexposure to bright light carries other direct health risks. It increases our risk of various types of cancer, depression, cardiovascular disease and diabetes. The prolonged, unnatural fluctuation or suppression of melatonin secretion has been directly linked to breast cancer, for example.

Minimising The Effects Of Light Pollution

1. Physical Barriers

When an object is solid and thick enough, not even the brightest light can penetrate it. Invest in a set of heavy curtains or solid blinds that completely cover your bedroom windows. This will help with direct light sources and sky glow outside. In certain cases a blindfold may help, although many consider it a napping tool, as it becomes uncomfortable when we sleep for longer.

2. Light Colour Temperature Control

As daylight progresses through the natural cycle, the colour temperature of the available light changes. Colour temperature is expressed in Kelvins (K) – where the light at the red-ish (warm) end of the spectrum has a low K reading, and light at the blue-ish (cool) end of the spectrum has a high K reading. These changes in daylight influence melatonin secretion – when we experience more blue light, our bodies secrete less melatonin.

That is why we struggle to fall asleep when we spend an evening staring at devices that use LED screens: they emit mostly blue light. The solution is either to forego screen time in the evening or to adjust the devices’ screens so they emit warmer colours closer to bedtime. Many operating systems cater to this adjustment already, or you can download apps that are purpose-built.

Recent developments in LED lighting enable us to choose warmer colours. Most LED-based lightbulbs have an indication of their colour temperature printed somewhere on the packaging. Go for the warm, low-K bulbs. Some LED lighting systems have an adjustable colour temperature, which you can control via an app on your cellphone.

3. Self-Awareness

Like charity, limiting light pollution starts at home. Take a critical look at your usage of bright lighting inside and outside your home. Only leave lights on at night when it is really necessary, and use infra-red sensors on floodlights outside so they would switch on only when they detect movement. Pay special attention to the reach of any lights outside, in order to avoid light trespass.

Negotiate with your neighbours or local government if you experience light pollution. The first step is to make them aware of the problem and its adverse effects.

For the warm glow of digital camaraderie, there are websites like, brimming with information, tips and resources. Spread the word – perhaps urban and suburban dwellers would be able to sleep soundly, and see the stars at night again soon.