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Home / Knowledge / The NBS Guide to Light Pollution

The NBS Guide to Light Pollution Design and Specification Health and Safety Specification Lighting Smart cities
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by Jess Sharman

Light pollution is an unwanted by-product of artificial light. It’s most problematic in urban settings where sources of artificial light are found en masse.

As the global population continues to urbanize, light pollution is becoming more problematic. To minimise its negative impact, we need to factor in lighting and its effects from the beginning of the planning and design stages.

Types of Light Pollution

There are several types of light pollution:

Sky glow – The brightness in the night sky caused by artificial light emanating upwards from dense urban areas. City dwellers often become so used to sky glow that they not only become oblivious to how much extraneous light is polluting their environment, they forget how beautiful a clear night sky can be.

Light trespass – When light falls where it wasn’t designed to, often creating a nuisance. For instance, residential security and street lighting that inadvertently illuminates a person’s bedroom. One of the biggest problems associated with light trespass is poor sleep; the body requires darkness to regulate itself and trigger the healthy, healing cycles necessary for good physical and mental health.

Over-illumination – Excessive lighting used to bring focus onto a structure or location. The Eiffel Tower and St Stephen’s Basilica (Szent István-bazilika) are good examples of using excessive lighting to highlight architecture.

Uplighting – Light that shines directly upward into the night sky, serving no practical purpose. Uplighting is a key contributor to sky glow, and over-illuminated structures often incorporate uplighting in their lighting scheme for additional effect.

Glare – Light so excessive and dazzling that it interferes with vision and/or causes visual distress. Typical sources of glare include direct or reflected sunlight, car headlamps, and unshielded security and street lighting.

Clutter – The excessive grouping of light sources often found in over-lit areas. Light clutter contributes to glare, trespass and sky glow.

Why is it a problem?

There are many reasons that light pollution is problematic. For one, sky glow has an adverse effect on astronomy. In 1994, during an earthquake in Los Angeles, the city’s power was knocked out. Emergency centres began receiving frantic calls about a “strange, giant, silvery cloud” in the sky. What these people were seeing was the Milky Way; they had become so accustomed to sky glow that they didn’t recognize one of our sky’s most prevalent features (Environmental Health Perspectives Journal, National Institute of Health, Volume 117, 2009).

Light pollution also has a negative impact on our health. Light trespass is a primary cause of disrupted and insufficient sleep. Darkness activates certain body functions that are intended to keep us healthy by promoting better sleep, triggering self-repair and helping fight conditions like depression. Light interrupts the body’s natural circadian rhythm and interferes with melatonin production, which is vital to the whole process. In fact, the lack of melatonin has been linked to cancer and there have been studies linking light pollution to obesity.

There is also the impact that light pollution has on nature. Dutch physiologist Frans Verheijen began studying its effects of animals in the 1950s, and a lot of research has been done since on how light pollution affects a variety of species. Then, in the 1970s, researchers started looking at its effects on other biological elements. All of this was brought together when Catherine Rich and Travis Longcore held a conference exploring the links between the different studies’ findings in 2002. From that came the book Ecological Consequences of Artificial Night Lighting (Island Press, 2006).

In the years since, scientists have become increasingly concerned about the severity of the effect that light pollution has on various ecosystems. Just as with humans, biological organisms rely on a cycle of dark and light to regulate behaviour.

While there are additional negative effects that we could explore, we will only touch upon one other very obvious impact here, and that is financial. Wasted light is wasted money. The more aware we become of the idea of light pollution the more we begin to realise just how prevalent it is in most of our lives. When factored over time, the costs – to individuals, to businesses, to municipalities – of this unnecessary and impractical lighting are huge. It's doubtful that Parisians would miss the Eiffel Tower - but they may not realise how much its uplighting masks the night sky above them


One of the more harmful changes in recent years is our move to LED lighting. While more energy efficient, LEDs emit a broad-spectrum white light that covers most of the frequencies that are important for natural world balance. Effects noted have included throwing migrating species off their path and causing an increase of disease in birds. Alarmingly, the effect on insects is one of the most detrimental, with a single LED-lit street lamp being able to kill billions in a single summer.

Glare bombs

Glare bombs comprise any light source that directs too much of its light sideways into the eyes or upwards into the sky. Glare bombing often happens when LEDs are retrofitted into an older structure like a car park or petrol station canopy. It’s also a problem with some security lighting designs. Glare bombs make trying to see uncomfortable, create temporary night blindness and can cause dark spots to form in front of your eyes. They can also create security risks.

Light pollution and safety

Despite opposite thinking, excessive and unshielded incorrectly directed lighting creates a security risk rather than eliminating it. A constantly glaring security light on a building, for instance, not only impairs vision of anyone using or walking through that space, it creates deeper shadows for would-be assailants or thieves to hide and move around in. The same goes for unshielded street lamps. The light illuminates upwards, creating shadows along the pathway and surrounding areas. Because these types of lights tend to provide a false sense of security, people’s guards are lowered, which puts them at additional risk.


Light pollution affects us all. It is an environmental concern, it wastes money and resources, it puts our health at risk, presents a danger to ecological systems and has an adverse effect on both flora and fauna. Therefore, it is an issue that needs to be addressed in any and every project that we being that includes lighting. In a future article, we will expand our exploration of light pollution as it relates to urban planning.


Light pollution – what is it and why is it important to know? Dark Skies Awareness
5 types of light pollution and their environmental impact. Treehugger
The problems of light pollution
The dark side of light: how artificial lighting is harming the natural world

Of visual interest: Jess Sharman

Technical content specialist at NBS

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