Helena Joyce
Light pollution is the human-made alteration of outdoor light levels from those occurring naturally. It is a form of waste energy that can have adverse effects on humans, wildlife, and the environment. Caused by artificial light, light pollution can come in several forms, including light trespass, over-illumination, light clutter, and sky glow. Sources of light pollution include boats, buildings, street lights, fireworks, and security floodlights. The impact of light pollution ranges from disrupting the natural body rhythms of humans and animals to causing a waste of money and resources.
| Characteristics | Values |
|---|---|
| Definition | The human-made alteration of outdoor light levels from those occurring naturally |
| Types | Light trespass, over-illumination, light clutter, sky glow |
| Sources | Boats, buildings, street lights, fireworks, mercury, metal halide, first-generation blue-light LED road luminaires |
| Effects on Humans | Sleep deprivation, fatigue, headaches, stress, anxiety, other health problems, reduced night sky visibility |
| Effects on Animals | Disrupts migration, reproduction, hunting, feeding, wake-sleep habits, habitat formation |
| Environmental Effects | Degrades environmental quality, increases air pollution, wastes energy, increases impacts of climate change |
| Economic Effects | The International Dark-Sky Association estimates that 1/3 of all lighting is wasted at an annual cost of $2.2 billion |
| Solutions | Use full cutoff lighting fixtures, shielded lights, dimming lights, turning off lights, using sodium lamps |
What You'll Learn
Artificial light
The use of artificial light has extended the length of the productive day, offering more time for work and recreational activities. However, when artificial outdoor lighting becomes inefficient, annoying, and unnecessary, it is considered light pollution. Light pollution is the presence of any unwanted, inappropriate, or excessive artificial lighting. It can be understood as a phenomenon resulting from a specific source or kind of pollution and as a contributor to the wider, collective impact of various sources of pollution.
Light pollution can have adverse effects on human health. Medical research suggests that light pollution or excessive light exposure can cause a variety of health issues, including increased headache incidence, worker fatigue, medically defined stress, decreased sexual function, and increased anxiety. Studies have also found a connection between reduced melatonin levels and cancer. Melatonin is a hormone that is released when it is dark and inhibited when there is light. An increased amount of light at night lowers melatonin production, which results in sleep deprivation, fatigue, headaches, stress, anxiety, and other health problems.
Light pollution also negatively impacts wildlife and the environment. It disrupts the lives of animals, affecting migration, reproduction, hunting, and feeding. Nocturnal light can interrupt sleep and confuse the circadian rhythm—the internal, twenty-four-hour clock that guides day and night activities and affects physiological processes in nearly all living organisms. Light pollution can also impact plant and animal physiology, confuse animal navigation, alter competitive interactions, change predator-prey relations, and cause physiological harm.
To reduce light pollution, simple solutions include shielding lights to reduce glare, dimming lights to provide the right amount of light, and turning off lights when they are not needed. The use of full cutoff lighting fixtures is also recommended, as they direct light only below the horizontal, reducing the amount of light wasted by directing it outwards and upwards.
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Energy waste
Light pollution, caused by artificial light, has a significant impact on both human health and the environment. It disrupts the lives of animals, affecting their migration, reproduction, hunting, and feeding, and habitat formation. It also interferes with human sleep patterns and can lead to health issues such as sleep deprivation, fatigue, headaches, stress, and anxiety.
The economic impact of this energy waste is significant. In the US alone, it is estimated that about 60 billion kilowatt-hours of energy are wasted annually, resulting in a financial loss of over $6.3 billion. Additionally, this wasted energy contributes to carbon dioxide emissions, with an estimated release of 23 billion pounds of CO2 into the atmosphere each year. To offset these emissions, 875 million trees would need to be planted annually.
The environmental consequences of energy waste due to light pollution are also severe. The generation of wasted electricity predominantly relies on coal-fueled power plants, which further exacerbates air pollution and contributes to climate change. It is estimated that fixing light pollution could have the same effect as removing 9.5 million cars from the roads, significantly reducing carbon emissions and improving air quality.
To address energy waste caused by light pollution, it is essential to improve lighting design and promote smarter use of light. This includes using shielded lights to reduce glare, dimming lights when possible, and turning off lights when they are not needed. Adjusting the type of lights used and ensuring proper spacing and positioning can also help reduce light pollution and minimize energy waste.
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Impact on human health
Light pollution, caused by the human-made alteration of outdoor light levels, has a significant impact on human health. It is considered one of the fastest-growing and most pervasive forms of environmental pollution, with over 80% of the world's population and 99% of Americans and Europeans experiencing its effects.
The primary concern regarding the impact of light pollution on human health is the disruption of natural body rhythms, including the circadian rhythm or the internal 24-hour clock that regulates day and night activities. Artificial light at night can interfere with the production of melatonin, a hormone released in the dark that is essential for maintaining healthy sleep patterns. Reduced melatonin levels due to light pollution have been linked to various health issues, including sleep deprivation, fatigue, headaches, stress, and anxiety. Recent studies also show a connection between reduced melatonin levels and cancer.
Additionally, light pollution has been associated with an increased risk of obesity, depression, sleep disorders, and diabetes. The American Medical Association estimates that white LED lamps have five times the impact on circadian sleep rhythms compared to conventional street lamps. Brighter residential nighttime lighting has been linked to reduced sleep times, dissatisfaction with sleep quality, excessive sleepiness, impaired daytime functioning, and obesity.
The negative effects of light pollution extend beyond human health. It also impacts wildlife, affecting the migration patterns, wake-sleep habits, and habitat formation of various species. Sea turtles and birds are particularly vulnerable to disorientation and death due to artificial lighting. Large numbers of insects, a primary food source for birds and other animals, are drawn to artificial lights and killed upon contact. Furthermore, light pollution contributes to energy waste and air pollution, with significant economic and environmental consequences.
While light pollution poses significant challenges, there are ongoing efforts to address them. These include adjusting the types of lights used, implementing full cutoff lighting fixtures, and supporting initiatives like the International Dark Sky Association's mission to preserve the natural night sky.
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Impact on wildlife
Light pollution has a significant impact on wildlife, affecting the natural behaviour of many species and disrupting their biological and ecological rhythms. Nocturnal animals are particularly affected by the drastic change in their environment, with predators hunting more effectively in the light and prey species losing their cover of darkness.
Migration and Navigation
Light pollution can disorientate animals that migrate or navigate at night, causing them to lose their way and often leading to their death. Sea turtles and birds, for example, rely on moonlight to navigate during migration, and artificial light can confuse them. Similarly, juvenile salmon are drawn to patches of water lit by artificial light, making them easy prey for predators.
Reproduction and Feeding
Light pollution can also interfere with the reproductive and feeding habits of wildlife. For example, the nocturnal activity of amphibians such as frogs and toads, which is part of their breeding ritual, is disrupted by artificial light. Insects, a primary food source for birds and other animals, are attracted to artificial lights and are killed upon contact. This decline in insect populations negatively impacts species that rely on them for food or pollination.
Roosting and Nesting
Bright lights can also affect the roosting and nesting habits of some species. The western snowy plover, for instance, avoids roosting on beaches where artificial light is brighter than the light of a half-moon. Newly hatched sea turtles need a dark night sky to orient themselves towards the sea, but artificial lights can lure them away from the water, making them vulnerable to predators.
Circadian Rhythm and Sleep
Artificial light at night can disrupt the natural sleep patterns of wildlife, affecting the production of the hormone melatonin, which is released in the dark and inhibited by light. This can lead to sleep deprivation, fatigue, and other health issues in affected animals.
Conservation and Biodiversity
Light pollution also has broader implications for wildlife conservation and biodiversity. It can alter the composition of ecosystems, favouring species that exploit the presence of light while putting others at a disadvantage. This can have cascading effects on food webs and ecological dynamics.
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Light fixture design
Light pollution, caused by the overuse and misuse of artificial light, is a pressing issue that affects humans, wildlife, and the environment. It disrupts natural body rhythms, negatively impacts animal behaviours, and has economic and environmental consequences. To address light pollution, it is essential to adopt better lighting practices and designs, such as using shielded light fixtures that direct light downwards, reducing glare, and minimizing light trespass.
When designing light fixtures to reduce light pollution, it is crucial to consider the installation angle, spectrum selection, lighting design, power supply configuration, and the use of lamp LEDs. Here are some key principles to guide the design of light fixtures for reducing light pollution:
- Installation Angle: Avoid shooting light at angles above the horizon. Choose solutions with glass or sunshades to reduce upward or backward light emission.
- Spectrum Selection: Ensure that the lateral light distribution is designed based on the width of the road and the height of the fixtures. Avoid under-designing the spectrum, as it may result in a tilting angle that directs light into the sky.
- Lighting Design: Emphasize functionality and direct light downwards, preferably with a narrow angle, to minimize sky glow. Consider using full cutoff lighting fixtures to prevent light from escaping upwards and outwards.
- Power Supply Configuration: Evaluate the power requirements and consider using intelligent control systems or timers to reduce illumination during certain periods, conserving energy and reducing light pollution.
- Lamp LEDs: Opt for LED modules that provide soft, diffused, and angled light. Warm LED tones can offer visual comfort and efficacy while minimizing light pollution.
By incorporating these principles into light fixture design, it is possible to reduce light pollution, conserve energy, minimize wildlife disruption, and improve overall lighting functionality.
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Frequently asked questions
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.
There are several types of light pollution, including:
- Light trespass: Unwanted light that enters another property, for example, by shining over a neighbour's fence.
- Over-illumination: Using excessive light where it is not needed.
- Glare: Excessive brightness that can cause visual discomfort, such as when driving.
- Light clutter: Redundant clusters of lighting found in many urban centres, such as in Times Square, New York City.
- Sky glow: The brightening of the night sky due to artificial lighting, commonly found over big cities.
Common sources of light pollution include street lamps, parking lot lights, exterior lights on homes and businesses, neon signs, and illuminated signboards. Buildings that operate 24/7, like hotels and convenience stores, also contribute significantly to light pollution. Poorly designed lighting at outdoor sports centres, fields, and stadiums can also cause increased light pollution.
Light pollution has harmful effects on both humans and wildlife. It can disrupt the natural day/night cycle, known as the circadian rhythm, leading to sleep disorders and potential health issues such as depression, hypertension, and attention deficit disorder. Light pollution also impacts animal behaviours, including migration patterns, wake-sleep habits, and habitat formation.
There are several ways to reduce light pollution, including adjusting light fixtures, using appropriate light bulbs, and implementing timers and sensors. Organisations like DarkSky International work with communities to establish codes and statutes that reduce light pollution and educate the public about its harmful effects. Individuals can also support these efforts by joining email lists and advocacy groups to stay informed and take action against light pollution.
