Light Pollution: City Lights And Their Unseen Impact

Light pollution is a human-made alteration of outdoor light levels from those occurring naturally. It is caused by excessive electric light use, especially at night, and is a significant issue in cities, where over three-quarters of residents have never experienced a naturally dark sky. Light pollution has detrimental impacts on wildlife, human health, safety, energy conservation, cost, and our ability to view the stars. It can confuse the migratory patterns of animals, alter competitive interactions, change predator-prey relations, and cause physiological harm. For humans, exposure to light during sleep can suppress melatonin production, leading to sleep disorders, increased headaches, worker fatigue, stress, and anxiety. Light clutter, glare, skyglow, and light trespass are all types of light pollution that can have negative effects on both humans and wildlife.

Excessive use of electric light

The excessive use of electric light is a significant cause of light pollution in cities. This phenomenon, known as "sky glow", is the brightening of the night sky due to the electric lights of cars, streetlamps, offices, factories, outdoor advertising, and buildings. The light reflects off smog, clouds, and other particles in the atmosphere, creating a bright haze that turns night into day.

Electricity has become relatively cheap over time, leading to over-consumption and excessive use, especially at night. The over-illumination or improper spectral composition of light has been linked to various adverse health effects, including increased headaches, worker fatigue, medically defined stress, decreased sexual function, and increased anxiety. Research also suggests a link between exposure to artificial light at night and an elevated risk of breast cancer, with female employees working night shifts found to have a higher breast cancer risk.

The excessive use of electric light also has detrimental impacts on wildlife, with studies showing that light pollution affects the behaviour of animals, including migration patterns, wake-sleep habits, and habitat formation. For example, sea turtles, birds, and juvenile seabirds guided by moonlight during migration get confused, lose their way, and often die due to artificial light interference. Frogs have been found to inhibit their mating calls when exposed to excessive light at night, reducing their reproductive capacity, while the feeding behaviour of bats is also altered.

Light clutter, a term used to describe the redundant clusters of lighting found in many urban centres, can generate confusion, distract from obstacles, and potentially cause accidents. Poor lighting placement and design can contribute to these issues and even be intentionally used to distract drivers.

To address the excessive use of electric light and its resulting light pollution, several solutions can be implemented:

• Turn off unnecessary lights.
• Use fully shielded, light-efficient fixtures to prevent light from escaping and reduce sky glow.
• Shield lights to reduce glare and improve visibility.
• Dimming lights to provide only the necessary amount of illumination.

Light clutter

To reduce light clutter, it is important to follow the Five Principles for Responsible Outdoor Lighting. This includes using light only when it is needed and ensuring that it has a clear purpose. Light should be directed so that it falls only where it is needed, using shielding and careful aiming to target the direction of the light beam so that it points downward and does not spill beyond where it is intended.

Glare

To reduce glare, it is essential to implement thoughtful lighting installations that direct light only where it is required and in the necessary amounts. This can be achieved through shielding, careful aiming, and the use of full cutoff lighting fixtures to ensure light does not spill beyond its intended area.

Additionally, the type of light used is crucial. For example, mercury, metal halide, and blue-light LED road luminaires are more polluting than sodium lamps as they scatter light more effectively in the atmosphere. Thus, evaluating and redesigning lighting plans, as well as appropriately spacing lights and using the right wattage, are recommended steps to mitigate glare.

Light clutter, or excessive groupings of lights, can also contribute to glare. This issue is often observed on roads with poorly designed street lights or bright advertisements, creating a contrast in illumination that interferes with night vision and can even lead to accidents. Therefore, addressing light clutter through proper lighting design and placement is vital to reducing glare and improving safety.

Light trespass

The impact of light trespass can be mitigated by using shielded lighting fixtures that direct light downward and prevent it from spilling onto neighbouring properties. In addition, timer or occupancy sensors can be used to turn off lights when they are not needed, reducing the amount of light trespass and light pollution.

To address light trespass, it is important to communicate with neighbours and work together to find solutions. While legal action is an option, it is advised to first try collaborative approaches, such as writing a letter, to resolve the issue and create a comfortable atmosphere for the community.

Sky glow

Light pollution, also known as sky glow, is a pressing issue that has been a concern for astronomers for decades. Sky glow is the bright haze above cities produced from excessive artificial lighting at night. It is caused by artificial light reflecting in the sky and bouncing off different particles in the atmosphere, such as air molecules, dust, and pollution. This light pollution is amplified by the presence of clouds and water droplets.

The breeding activity and reproductive phenology of toads, for example, are cued by moonlight, which can be disrupted by light pollution. Sea turtle hatchlings emerging from nests on beaches are also impacted by sky glow, as they find the ocean by moving away from the dark silhouette of dunes and vegetation. Artificial lights interfere with this natural navigation, leading to high mortality rates.

Additionally, sky glow can have detrimental impacts on human health. Medical research suggests that excessive light exposure can lead to adverse health effects, including increased headaches, worker fatigue, medically defined stress, decreased sexual function, and increased anxiety.

To address the issue of sky glow, organizations like DarkSky International and the International Dark-Sky Association have developed policies and standards for responsible outdoor lighting. These initiatives aim to reduce light pollution and protect the visibility of starry skies.

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