Kiera Jefferson
Light pollution is a side effect of industrialization, caused by human-made alterations of outdoor light levels from those occurring naturally. Sources of light pollution include building exterior and interior lighting, advertising, outdoor area lighting, offices, factories, streetlights, and illuminated sporting venues. It is most severe in highly industrialized, densely populated areas of North America, Europe, and Asia, and in major cities in the Middle East and North Africa. There are four main types of light pollution: skyglow, glare, light trespass, and clutter.
| Characteristics | Values |
|---|---|
| Number of main types | 4 |
| Causes | Human development, thoughtless behaviours, poor light fixture design, overlighting, failure to use timers and sensors, wrong colour/temperature of light |
| Sources | Building exterior and interior lighting, advertising, outdoor area lighting (e.g. car parks), offices, factories, streetlights, illuminated sporting venues, wind turbines, boats, fireworks |
| Effects | Obstructs starlight, causes eye discomfort, sleep deprivation, fatigue, headaches, stress, anxiety, interrupts migration patterns, mating practices, feeding behaviour, sleep cycles, and habitat formation |
| Solutions | Using light sources of minimum intensity necessary, turning off lights when not needed, improving lighting fixtures, adjusting the type of lights used, using light shields, using lightbulbs that require lower wattage |
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What You'll Learn
Skyglow
The sources of skyglow include building exterior and interior lighting, advertising, outdoor area lighting (such as car parks), offices, factories, streetlights, and illuminated sporting venues. It is most severe in highly industrialised, densely populated areas of North America, Europe, and Asia, as well as in major cities in the Middle East and North Africa, such as Tehran and Cairo. Even relatively small amounts of light can contribute to skyglow, and its effects are magnified at night due to the contrast with the sky's darkness.
The impact of skyglow is far-reaching. It reduces the visibility of celestial objects, affecting astronomers and stargazers alike. It also disrupts the natural rhythms of both humans and wildlife, impacting sleep and other physiological processes. Furthermore, it contributes to energy waste and negatively affects the environment.
The problem of skyglow has led to the emergence of a global dark-sky movement, with organisations such as the International Dark-Sky Association advocating for the reduction of light pollution. Efforts to mitigate skyglow include improving lighting fixtures, utilising timers and sensors, choosing appropriate light sources, and establishing lighting ordinances in certain cities. Despite these efforts, the area affected by artificial illumination continues to increase, and the majority of the world's population lives under light-polluted skies.
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Glare
The glare from light pollution is often caused by the density, design, or improper use of light fixtures. For example, the use of mercury, metal halide, and first-generation blue-light LED road luminaires can cause more glare than sodium lamps as the Earth's atmosphere scatters and transmits blue light more effectively than yellow or red light. This can be observed as "glare" and "fog" around and below LED road luminaires when air humidity is high.
To reduce glare, it is recommended to use full-cutoff lighting fixtures, which direct light only below the horizontal, minimising light wasted by directing it outwards and upwards. Flat-lens cobra luminaires are an example of this type of fixture and are commonly required in Italian regions to achieve "zero upward light". Additionally, it is important to space lights appropriately and match the number and wattage of luminaires to the lighting needs.
The negative impacts of glare on human health have been recognised, with the American Medical Association developing a policy in support of controlling light pollution in 2009. Excessive brightness can cause sleep disruption and melatonin suppression, leading to potential long-term health risks.
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Light trespass
In some areas, such as unincorporated regions of Riverside County, California, light trespass is illegal, and violators may face fines or even jail time. To address light trespass, several cities in the U.S. have developed standards for outdoor lighting, and the International Dark-Sky Association has created model lighting ordinances to protect citizens' rights.
Overall, light trespass is a significant concern, impacting the lives and privacy of many individuals. Preventative measures and regulations are crucial to reducing its occurrence and mitigating its negative effects on communities and astronomical research.
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Clutter
The design and placement of lights can be intentionally distracting. For example, bright lights surrounding roadways can be intended to distract drivers, thereby contributing to accidents.
Light clutter is a major side effect of urbanization. It is most severe in highly industrialized, densely populated areas of North America, Europe, and Asia, as well as in major cities in the Middle East and North Africa, such as Tehran and Cairo. Even relatively small amounts of light can be noticed and create problems.
Light pollution is the human-made alteration of outdoor light levels from those occurring naturally. It is caused by the inefficient or unnecessary use of artificial light. Common sources of light pollution include street lamps, parking lot/shopping mall lights, exterior lights found on most homes/businesses, neon signs, and illuminated signboards.
Light pollution has harmful effects on human health, wildlife, and the climate. It disrupts the natural day/night cycle of 12 hours of natural light and 12 hours of darkness, which is an essential biological imperative. Disruption of this cycle, known as the circadian rhythm, has been linked to sleep disorders, depression, hypertension, attention deficit disorder, obesity, diabetes, and heart disease.
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Excessive artificial lighting
The effects of excessive artificial lighting are magnified at night, when the contrast with the sky's darkness is most noticeable. This type of pollution can have detrimental effects on both human health and the environment. For humans, exposure to artificial light at night can disrupt natural body rhythms, including the circadian rhythm and the production of the hormone melatonin, which can lead to sleep deprivation, fatigue, headaches, stress, anxiety, and other health problems.
Wildlife is also significantly impacted by excessive artificial lighting. Many species rely on natural light conditions to complete critical life functions such as reproducing, migrating, feeding, sleeping, and forming habitats. Light pollution can confuse wildlife, as it mimics celestial light. Nocturnal animals, in particular, are affected by light pollution, as they depend on the cover of darkness for hunting and hiding. Additionally, artificial lighting can alter marine ecosystems, as demonstrated by a study that showed fewer filter-feeding animals near brightly lit panels submerged off the coast of Wales.
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Frequently asked questions
The four main types of light pollution are skyglow, glare, light trespass, and clutter.
Skyglow is the most well-known form of light pollution. It is caused by unshielded, reflected, and upwardly directed city lights, creating an artificially bright arch in the sky. It obstructs starlight and makes the sky appear starless.
Glare is scattered light that bounces off reflective objects at night, causing visual discomfort and even temporary blindness. Drivers often experience glare from street lights, signs, and other cars' headlights.
Light trespass occurs when light extends into an area where it is not wanted or needed, such as a streetlight shining into a bedroom window.
