31 March 2022

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

As the global population urbanizes, light pollution is becoming more problematic. To minimize 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:

Skyglow – The brightness in the night sky resulting from artificial light emanating upwards from dense urban areas. City dwellers have become so used to sky glow that they are unconscious of how much extraneous light pollutes their environment and either have forgotten or never known how beautiful a clear night sky can be.

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

Over illumination – Excessive lighting that intentionally focuses on and around a structure or location. The Eiffel Tower and St Stephen's Basilica (Szent István-bazilika) are good examples of architecture incorporating excessive lighting.

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

Light trespass – Lighting that illuminates where it isn't designed to, often creating a nuisance. For instance, security and street lighting trespassing into a person's bedroom and interfering with sleep. The body requires darkness to regulate itself and trigger the healthy healing cycles necessary for good physical and mental health; however, in many communities, security and pathway lighting is situated with disregard to housing window location.

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 numerous ways that light pollution is problematic. A few examples include:

It harms our health. Darkness activates certain body functions 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 vital melatonin production. A lack of melatonin leads to higher cancer risk, and studies have also linked light pollution to obesity.

It can reduce safety in outdoor areas. Despite opposite thinking, excessive and unshielded, incorrectly directed lighting creates an additional security risk rather than eliminating it. For instance, a continuously glaring security light on a building impairs the vision of anyone using or walking through that space. Excessive, unshielded lighting also creates deeper shadows for would-be assailants or thieves to hide and move around in. The same goes for unshielded streetlamps. The light illuminates upwards, creating shadows along the pathway and surrounding areas. Because these lights provide a false sense of security, people's guards are lowered, which puts them at additional risk.

It negatively impacts flora, fauna and their ecosystems. Scientists are becoming increasingly concerned about the severity of light pollution's effect on various ecosystems. Just as with humans, biological organisms rely on a cycle of dark and light to regulate behaviour.

Dutch physiologist Frans Verheijen began studying light pollution's effects on animals in the 1950s, and, in the 1970s, researchers began looking at its impact on other biological elements. In 2002, Catherine Rich and Travis Longcore held a conference exploring the links between the different studies' findings, resulting in the publication of Ecological Consequences of Artificial Night Lighting (Island Press, 2006). In 2020, several researchers reviewed studies performed over the last few decades. They catalogued the findings to create an over-arching view of how artificial light at night (ALAN) affects living species and their environments in a peer-reviewed paper entitled Exposure to Artificial Light at Night and the Consequences for Flora, Fauna, and Ecosystems.

It adversely affects astronomy and hinders our and astronomers' ability to observe our universe. In 1994, during an earthquake, the city of Los Angeles, California, lost power. Emergency centres received frantic calls about a "strange, giant, silvery cloud" in the sky. This strange phenomenon was, in fact, the Milky Way. People have become so accustomed to sky glow that they no longer recognize one of our sky's most prevalent features (Environmental Health Perspectives Journal, National Institute of Health, Volume 117, 2009).

Wasting light wastes money. The more aware we become, the more we realize how prevalent light pollution is in most of our lives. When factored over time, the additional costs of 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

LEDs, glare bombs and colour temperature

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 vital to natural world balance. Noted effects include throwing migrating species off their path and causing an increase in bird disease. Alarmingly, the impact on insects is one of the most detrimental, with a single LED-lit streetlamp being able to kill billions in a single summer.

Retrofitting LEDs into an older structure, like a car park or petrol station canopy, can result in glare bombing, which is when a light source directs too much of its light sideways into the eyes or upwards into the sky. Glare bombing can also be a problem with some security lighting designs. Glare bombs make trying to see uncomfortable, create temporary night blindness, and cause dark spots to form in front of your eyes. They can also create security risks.

LED colour is also an issue. Higher colour temperature LEDs contain a significant amount of blue light, which can cause severe harm to human and natural ecosystem health. Even the white light emitted at a lower colour temperature can be harmful; however, it is preferable to a bright bluer white. In places that encroach upon natural areas and habitats, LPS or low-spectrum LEDs are the better choices.

Things to think about when specifying

Combating light pollution is an essential part of sustainable design and specification. When specifying for lighting, consider the undesirable effects discussed above and carefully weigh the effects of lighting design and product choices against their potential negative impact. For instance, specify lighting that:

  • illuminates specifically-required areas only,
  • is fully shielded and pointing downward,
  • is no brighter than necessary,
  • minimizes blue light emissions, and
  • turns on only when needed.


  • Designs and products that unnecessarily allow light to escape above the horizon (via poorly designed, wrongly specified, wrongly installed luminaires.
  • Light levels that are too high and increase reflection from illuminated surfaces.
  • Lighting designs that allow light to stray where it is unwanted and unneeded. For instance, into the sky or towards dwellings.
  • LED lights that fall within the higher, cool blue-white colour range, opting for lights within the 3,000K range.

Additional sustainability resources


You can read about NBS's commitment to sustainability on our Sustainability with NBS webpage. This page also includes links to our sustainability webinars and articles, including The three pillars of sustainability, which provides an overarching view of how sustainability is assessed. Also of benefit is an article on the importance of specification, especially in the digital age.

RIBA Plan of Work 2020 and the Sustainable Outcomes Guide

With the 2020 release of the RIBA Plan of Work, the RIBA has responded to an escalating industry need for an expanded sustainability strategy by mapping sustainability targets to UN Sustainable Development Goals and aligning them with the RIBA Sustainable Outcomes Guide. To explore this and other ways that the new Plan of Work can benefit you, NBS has a webinar series that addresses several topics, including sustainability, fire safety, conservation and inclusive design.

NBS Chorus

NBS has also seen a steady rise in requests for information on how our technical content can help specifiers achieve sustainable outcomes. In the article Using NBS to specify sustainable outcomes on projects, NBS explores how the Plan of Work and NBS's flexible cloud-based specification platform can be used together to tailor a project to meet sustainability expectations across the project timeline. Through NBS Chorus, you can access your specifications across locations and organizations. Chorus is suited to performance and prescriptive specifying and has editable clauses supported by technical guidance. Our content is reviewed to improve clarity and usefulness, informed by research, user feedback and industry drivers.

NBS Source

NBS Source brings together NBS BIM Library, NBS Plus and RIBA Product Selector to provide a sole source for product information that seamlessly integrates into a project's workflow and provides an additional level of enhanced product data in a consistent, structured format. Many of the manufacturers listed include environmental and sustainability information in their product listings.

The Construction Information Service

CIS is a comprehensive online collection of industry-relevant publications from around 500 publishers. NBS users with a CIS subscription can use embedded links across specifications platforms to access research and reference documents. The content is fully searchable, intelligently classified and continuously updated, and there is a generous amount of sustainability content that can be searched and referenced.