Artificial light is an essential part of our modern way of life. It underpins every part of our social infrastructure. Artificial light makes our hospitals workable throughout the year and night, our roads and transport system safe, our streets at night easier to navigate, and allowing us to have fulfilling and productive days throughout the year, even in the early darkness of winter nights.
But our heavy reliance on it, particularly when it is installed and managed irresponsibly, causes manifold problems for our health, our wildlife, and for our sense of who we are. One of the most grounding and contemplative experiences that a human being has is looking up to the sky and seeing the distantly scattered stars, glinting.
What can we do to ensure that we are reaping the benefits of artificial light, without doing harm?
What do we mean by ‘light pollution’?
What you probably imagine is ‘artificial sky glow’, it’s the light that is observable from space at night, or the haze that emanates from above the city skyline. This is what stops us seeing the stars. Back in 2016, an extensive survey of sky glow was conducted by Italian Scientist Fabio Falchi. From the satellite data he gathered, he estimated that the Milky Way was no longer visible to one-third of humanity. He estimated that 60 per cent of Europeans and 80 per cent of North Americans would no longer see the Milky Way at night (F. Falchi, et al., CC BY-NC)
Explore an interactive map of global light pollution here.
There are other kinds of light pollution too. Glare, clutter, and light trespass. These are less well known that sky glow, but are just as concerning and arguably have a greater impact on our daily lives. Glare is excessive brightness that can cause visual discomfort. This can be particularly dangerous, when driving. Clutter is intense, bewildering, and excessive groupings of light sources (for example, Times Square in New York City, or London’s West End). Light trespass is when light seeps into an unsuitable and undesirable area. A good example of this is a streetlight illuminating your bedroom, or light from a 24hr supermarket spilling into your garden.
The first UK law tackling light pollution came into force in 2006 under Section 102 of the Clean Neighbourhoods and Environment Act (2005). Exterior lighting joins noise and smells on a list of Statutory Nuisances, empowering the Environmental Health Department to take legal action against disruptive light emitted from premises.
There are also extensive government recommendations regarding lighting for new developments and in planning proposals, which seek to protect the environment and wildlife. For example, white or ultraviolet light is unlikely to be permitted close to protected sites, sensitive wildlife areas, particularly where it is likely to shine on water where bats feed. The recommendations do not include much reference or consideration of the impact on human health and behaviour.
What is the impact of Light Pollution on Your Health?
In the areas of the world that experience the most light pollution (in mega cities like London, for example), we don’t experience true night. The light level we experience is much closer to twilight than to real dark. That’s why starlight isn’t visible.
In extreme cases, living under round the clock artificial light means that our eyes cannot fully dark-adapt, the evolutionary feature that allows us to orient ourselves and see vague shapes at night (you might have relied on this power when camping, for example).
Our sleep and wake cycle is called a circadian rhythm. The cycle also affects hunger, activity, hormone production, and body temperature. The cycle lasts roughly 24 hours, and it relies on light signals. We are more energetic when it is sunny, when it is bright, and we feel sleepy as it gets dark. If we are constantly exposed to high levels of light, it has been observed that we suppress our production of melatonin - the hormone that makes us sleepy.
Though satellite observable sky glow isn’t intense enough to suppress melatonin production, we have to remember that this glow is the scattering of light from local sources. Those local sources are much more intense and are likely sufficient to trigger circadian disruption. The lighting inside your home after sunset, particularly if you use bright, white lights, may be impacting your sleep. Problems with our circadian rhythms can also lead to obesity, depression, cancer and other illnesses.
What can we do?
Shielding street lights
One easy solution is to use only fully shielded street lights that are designed to cast light down and direct it to where it’s most effective, while minimising glare and sky glow.
Keep light inside
Buildings that do not need to be lit up at night, should not be. The biggest source here are large commercial buildings that stay open and populated throughout the night. As we design these buildings, we should consider how this light can be directed downwards, prevented from extending into the sky. In our homes, we should use blinds to prevent the light from escaping to the street, or streetlight spilling into our bedrooms.
Be inspired by Sunset
To protect our circadian rhythms, we can use light sources that are appropriate for the time of day. Bright light with high blue content (eg, compact fluorescent) in the morning, and dim light, warmer light with low blue content (eg, low wattage incandescent) as dusk begins to settle.
Directional Lighting
In your lighting designs, avoid up-lighting (particularly outside) and use directional lighting to only light the things that need to be lit. Ensure that all lighting colour and brightness can be adjusted throughout the day, and that lights are easy and convenient to switch off.
Protect our Dark Skies
And, as for star-gazing, we must protect intrinsically dark landscapes. Those rare landscapes that are largely free from artificial light. National parks and nature reserves, which support habitats for native nocturnal animals.
References:
https://www.bbc.com/future/article/20160617-what-rising-light-pollution-means-for-our-health
https://www.gov.uk/guidance/light-pollution
https://www.lightpollutionmap.info/#zoom=3.76&lat=53.3447&lon=-0.0476&layers=B0TFFFFFFFFFFFFFFFF
https://www.nationalgeographic.org/article/light-pollution/
https://futurism.com/light-pollution-how-does-it-impact-people
https://www.nhm.ac.uk/discover/light-pollution.html