Light Pollution: Is It A Real Threat?

Light pollution is a pressing issue that has harmful effects on both humans and wildlife. It refers to the human-made alteration of outdoor light levels from those occurring naturally, caused by the excessive or inappropriate use of artificial light. This phenomenon has led to adverse health effects, disrupted ecosystems, and impaired our ability to observe the night sky. Light pollution is a global problem, with 83% of the world's population living under light-polluted skies. It has received less attention compared to other types of pollution, but it is a significant concern that needs to be addressed.

Light pollution's impact on human health

Light pollution, caused by the human-made alteration of outdoor light levels from those occurring naturally, has been shown to have adverse effects on human health. The excessive or inappropriate use of outdoor artificial light negatively impacts human health, wildlife behaviour, and our ability to observe stars and other celestial objects.

The artificial light from sources such as streetlights, cars, offices, and buildings can interfere with the natural body rhythms of humans and animals. This nocturnal light interrupts sleep and confuses the circadian rhythm, the internal 24-hour clock that guides day and night activities and affects physiological processes. The production of the hormone melatonin, which is released in the dark, is inhibited when there is light present. Lowered melatonin production due to increased light at night can result in sleep deprivation, fatigue, headaches, stress, anxiety, and other health issues.

Recent studies have also found a link between reduced melatonin levels and cancer. The American Medical Association (AMA) has recognised the potential risks of exposure to light at night, with white LED lamps estimated to have five times the impact on circadian sleep rhythms compared to conventional street lamps. Brighter residential lighting has been associated with reduced sleep times, dissatisfaction with sleep quality, excessive sleepiness, impaired daytime functioning, and obesity.

Light pollution has also been linked to an increased risk of depression, sleep disorders, diabetes, and breast cancer. The impact of light pollution on human health is a growing concern, with 80% of the world's population and 99% of Americans and Europeans living under light-polluted skies.

To mitigate the effects of light pollution on human health, it is essential to reduce excessive artificial lighting, use timers and sensors, and choose lighting that emits less polluting light waves, such as sodium lamps instead of blue-light LEDs.

The environment and light pollution

Light pollution is the human-made alteration of outdoor light levels from those occurring naturally. It is a side effect of industrial civilization, with sources including building exterior and interior lighting, advertising, commercial properties, streetlights, and illuminated sporting venues.

The environment is significantly impacted by light pollution. Firstly, it disrupts the natural cycles of light, affecting the illumination of the environment. This has a profound effect on nocturnal animals, as it turns night into day, disrupting their nocturnal activities and reproductive behaviours. For example, the glare from artificial lights can impact the breeding rituals of amphibians such as frogs and toads. Moreover, light pollution can lead to attraction or repulsion and orientation or disorientation responses in animals. Small nocturnal mammals may be repelled by artificial light sources, perceiving them as a potential risk of predation. In contrast, nocturnal insects and migratory birds may be attracted to the light, causing them to collide with structures or sustain injuries from lamps.

Light pollution also affects plants, as they rely on the predictable rhythm of day and night, encoded in their DNA, for various physiological processes. Furthermore, it has been found that city lights decrease the nighttime cleansing of the atmosphere and reduce the removal of nitrogen oxides, impacting air quality.

Additionally, light pollution compromises human health. Nocturnal light interrupts sleep and disrupts the circadian rhythm, affecting the production of the hormone melatonin. Reduced melatonin levels have been linked to sleep deprivation, fatigue, headaches, stress, anxiety, and an increased risk of cancer.

The good news is that light pollution is reversible. To combat this issue, people can advocate for local legislation to reduce light pollution, choose better outdoor lighting, and support organizations dedicated to restoring the nighttime environment, such as DarkSky International. Additionally, individuals can take immediate measures to limit artificial light at night in their homes and communities.

Light pollution and wildlife

Light pollution, caused by excessive artificial lighting, negatively impacts wildlife behaviour and ecosystems. It disrupts the natural rhythm of day and night, affecting the physiological processes of many organisms.

Light pollution affects both diurnal and nocturnal species, although in different ways. Diurnal species, such as bees, songbirds, and humans, are active during the day and sleep at night. Light pollution can extend the day for these species, making them more susceptible to predators or causing them to breed prematurely. Nocturnal species, such as moths, bats, frogs, and cats, are active at night and sleep during the day. Artificial light can attract or repel these organisms, resulting in habitat loss or disruption of their natural behaviours.

Some specific examples of how light pollution impacts wildlife include:

• Moths, frogs, and sea turtles are attracted to artificial lights, which can exhaust and kill them.
• Migratory birds are drawn to lights, which can bleach their visual pigments, causing them to lose sight of the horizon and circle endlessly.
• Songbirds in well-lit areas are more vulnerable to predators as they reveal their location by singing.
• Chinook and sockeye salmon in Washington state's Lake Washington are attracted to lit patches of water, becoming easy prey for predators.
• Cougars, despite their fearless reputation, will not cross brightly lit areas, demonstrating how artificial light can create barriers and fragment habitats.

To mitigate the effects of light pollution on wildlife, it is recommended to use low-pressure sodium lights or amber LEDs, which emit longer wavelength lights that appear dimmer to nocturnal animals. Additionally, shielding lights and mounting fixtures low to the ground can reduce glare and minimise the impact on animals' day/night patterns.

Economic effects of light pollution

Light pollution refers to the excessive or obtrusive use of artificial light caused by poor lighting design. It has been described as "one of the most rapidly increasing alterations to the natural environment". Light pollution has significant economic costs, including:

Negative impacts on wildlife

Light pollution has been shown to negatively impact wildlife behaviour, including migration patterns, wake-sleep habits, and habitat formation. For example, sea turtles are harmed by light pollution, as adult female sea turtles seek out dark beaches to lay their eggs, but they will not come ashore to do so if there are too many lights. Birds are also affected, with many cities adopting a "Lights Out" program to turn off building lights during bird migration.

Health impacts

Light pollution has been found to have negative impacts on human health, including disrupting the body's biological clock and hampering sleep cycles. Artificial light has also been linked to "all forms of cancer". This has convinced organisations such as the American Medical Association to support efforts to control light pollution.

Energy consumption

Light pollution wastes energy, with higher lighting levels than necessary resulting in significant economic consequences. In the US alone, outdoor lighting uses about 120 terawatt-hours of energy annually, contributing to global warming and climate change.

Astronomy

Light pollution also impacts our ability to observe stars and other celestial objects, with most people unable to see the natural night sky due to light pollution. This has implications for scientific research.

Light pollution and astronomy

Light pollution is the human-made alteration of outdoor light levels from those occurring naturally. It is caused by the excessive or inappropriate use of outdoor artificial light, which affects human health, wildlife behaviour, and our ability to observe stars and other celestial objects.

Astronomy and Light Pollution

Astronomers are concerned about light pollution as it reduces their ability to view celestial objects. Light pollution has been measured from space, but orbiting satellites do not detect light in the same way that the human eye does, so results may not match what is seen from the ground. Citizen scientists and researchers found that we are losing our view of the sky at a rate of almost 10% each year.

The night sky is a source of wonder and beauty, and stargazing is a pastime that has been enjoyed by humans for most of our existence. Light pollution is causing a sense of 'sky grief' in those who can no longer see the stars, as well as a loss of cultural identity and practices associated with stargazing.

Light pollution is a particular concern for amateur astronomers, who often do not have access to truly dark skies. Light pollution can degrade diffuse objects such as comets, nebulae, and galaxies, and makes it difficult to observe unusual or borderline celestial phenomena.

There are some steps that astronomers can take to mitigate the effects of light pollution, such as using light pollution filters, advocating for darker skies, and working with neighbours to reduce the impact of artificial light.

Frequently asked questions