Light And Air Pollution: Astronomy's Bane

Light pollution is the presence of any unwanted, inappropriate, or excessive artificial lighting. It is a major problem for astronomers, who are increasingly unable to view the night sky in its natural state. Light pollution is caused by inefficient or unnecessary use of artificial light, such as light trespass, over-illumination, glare, light clutter, and skyglow. These issues can often be easily addressed by adjusting light fixtures or using more appropriate light bulbs.

Air pollution can amplify the effects of light pollution, with dust and smoke scattering sky-bound radiation and further brightening the sky.

Light pollution has a number of adverse effects on human health, wildlife, and the environment. It interferes with the human body's light-driven circadian clock, prolonging the time it takes to fall asleep. It also poses a serious threat to nocturnal wildlife, disrupting the natural diurnal patterns of light and dark that orchestrate the rhythm of life.

Astronomers are campaigning for better lighting practices to reduce light pollution and protect the night sky, which is an important part of our global heritage.

Light pollution's impact on human health

Light pollution has a significant impact on human health, affecting both our mental and physical well-being. Here are some ways in which light pollution influences our health:

Sleep Disorders and Circadian Rhythm Disruption

Artificial light at night can disrupt the natural circadian rhythm, our internal 24-hour clock that governs sleep-wake patterns. This disruption can lead to sleep disorders such as shift-work sleep disorder and delayed sleep-phase syndrome. It can also result in sleep deprivation, fatigue, headaches, stress, and anxiety. The excessive use of artificial light extends the day, altering our natural sleep patterns and affecting our health.

Melatonin Suppression

Light pollution suppresses the production of melatonin, a hormone that regulates sleep, boosts the immune system, and has antioxidant properties. Lower melatonin levels are associated with an increased risk of cancer, especially breast cancer. Studies have found a correlation between outdoor artificial light at night and a higher risk of developing breast cancer.

Obesity and Diabetes

The American Medical Association (AMA) has stated that white LED lamps have five times the impact on circadian sleep rhythms compared to conventional street lamps. Brighter residential lighting at night is linked to reduced sleep duration, dissatisfaction with sleep quality, excessive sleepiness, and impaired daytime functioning, which can contribute to obesity.

Mental Health Issues

Light pollution can negatively impact mental health, with increased exposure to artificial light at night being associated with a higher risk of depression. The disruption of the circadian rhythm has also been linked to depression and other mental disorders.

Glare and Visual Discomfort

Poorly shielded outdoor lighting can cause glare, reducing visual contrast and decreasing our ability to see potential dangers at night. This visual discomfort can affect our safety, especially for older individuals with aging eyes.

Other Health Risks

In addition to the issues mentioned above, light pollution has been linked to an increased risk of cardiovascular disease and early-onset diabetes. The suppression of melatonin can also impact the functioning of the thyroid, pancreas, ovaries, testes, and adrenal glands.

Light pollution's effect on wildlife

Light pollution has a significant impact on wildlife, affecting their daily activities and natural behaviours. For billions of years, life on Earth has relied on the predictable rhythm of day and night, which is encoded in the DNA of plants and animals.

Impact on Nocturnal Animals

Light pollution alters the nighttime environment for nocturnal animals, turning night into day. Predators that hunt using light are impacted, as are prey species that rely on the cover of darkness. Research scientist Christopher Kyba notes that artificial light is likely the most drastic change humans have made to the environment for nocturnal animals.

Impact on Reproduction and Population

Light pollution can interfere with the breeding and reproduction of certain species. For example, the nighttime croaking of frogs and toads, which is part of their breeding ritual, is disrupted by artificial lights in wetland habitats. Artificial lights can also impact the migration and navigation of birds, causing them to wander off course and collide with illuminated buildings and towers.

Impact on Food and Shelter

About half of all life on Earth begins daily activities at sundown. Light pollution constrains the time these species have to find food, shelter, or mates, and it also exposes them to predators.

Impact on Plant Life

Different types of lighting can interfere with the well-being of plants. For example, white light sources, such as metal halides, CFLs, or LEDs, emit high levels of bluish light that can interfere with plant health.

Impact on Human Health

Light pollution also has indirect effects on humans by disrupting the natural cycles of plants and animals that we rely on for food and other resources. Additionally, it can impact our sleep by suppressing melatonin levels in our brains, making it harder to fall asleep.

Light pollution's role in energy wastage

Light pollution is a human-made alteration of outdoor light levels from those occurring naturally. It is caused by inefficient or misused light fixtures that scatter light above the horizontal plane. This form of pollution has harmful effects on wildlife, ecosystems, energy consumption, and climate change.

The adverse effects of light pollution on energy wastage are significant. It is estimated that at least 30% of all outdoor lighting in the US is wasted, mostly by lights that are unshielded. This adds up to a release of 21 million tons of carbon dioxide per year and a monetary cost of $3.3 billion. Globally, the energy used to generate light that escapes into space is estimated to be at least 1% of global greenhouse gas emissions, costing at least $50 billion annually.

The inefficiency of light pollution results in a substantial waste of energy and money, with serious environmental consequences. The excessive use of unshielded lights contributes to the unnecessary release of carbon dioxide, leading to an estimated cost of $4.5 billion in the United States alone.

To address this issue, it is recommended to install quality outdoor lighting that is fully shielded and directs light downwards. This simple change can cut energy use by 60-70%, saving billions of dollars and reducing carbon emissions. Additionally, unnecessary indoor lighting, such as in empty office buildings at night, should be turned off to prevent light leakage into the night sky.

By transitioning to energy-efficient LED lighting fixtures and implementing lighting control systems, significant energy savings can be achieved. It is estimated that the US could save at least $15.4 billion annually by 2035 by adopting these measures.

Light pollution is not just an issue for astronomers; it has far-reaching consequences for the environment, human health, and economies worldwide.

Light pollution's impact on astronomy equipment

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 of pollution or as a contributor to the wider, collective impact of various sources of pollution. Light pollution competes with starlight, interferes with astronomical observatories, and disrupts ecosystems and human health.

The impact of light pollution on astronomy equipment is significant. Telescope users can add dew shields, eyepieces, and camera filters to counteract light pollution from nearby sources like streetlights, but these methods will not target broad regions of the spectrum.

The most annoying and destructive problem is light that beams directly into your eye from a bright bulb. This is called glare and is often the easiest problem to avoid. You can set up your telescope in a shadowy corner, erect a tarpaulin to shade the telescope, or negotiate with your neighbours or local government to have the offending light turned off or replaced with a modern one of better design.

Light pollution also includes light trespass, which occurs when unwanted light enters your property, for example, by shining over a neighbour's fence. A common problem is when a strong light enters a window from outside, causing issues such as sleep deprivation.

Light clutter refers to excessive groupings of lights that may generate confusion, distract from obstacles, and potentially cause accidents. Clutter is particularly noticeable on roads where street lights are badly designed or where brightly lit advertisements surround the roadways.

Skyglow is what the term "light pollution" properly denotes. A typical suburban sky today is about 5 to 10 times brighter at the zenith than the natural sky. In city centres, the zenith may be 25 or 50 times brighter than the natural background.

Full-cutoff shielding in light fixtures is the essential remedy for both glare and skyglow. A lamp should send all its light downwards, not upward or sideways. "Full cutoff" means that no light rays from the fixture go above the horizon, and that at least 90% of the light is blocked in the near-sideways range from 0° to 20° below the horizontal plane.

Light pollution can be reduced by:

• Using light sources of minimum intensity necessary to accomplish the light's purpose.
• Turning off lights when not needed, using timers or occupancy sensors.
• Improving lighting fixtures so they direct their light more accurately towards where it is needed.
• Adjusting the type of lights used, so the light waves emitted are less likely to cause severe light pollution problems.
• Evaluating and re-designing lighting plans.
• Improving lighting fixtures by using full cutoff lighting fixtures, spacing lights appropriately for maximum efficiency, and matching the number and wattage of luminaires to the needs of the application.

Light pollution's effect on the environment

Light pollution is the presence of excess artificial light, resulting from urbanization and industrialization. It has far-reaching consequences for the environment, affecting plants, animals, and the ecosystem as a whole.

Impact on Plants and Animals

Light pollution disrupts the natural 24-hour cycle of plants and animals, which rely on light and dark for various life-sustaining behaviours. This disruption can have cascading effects on mating, migration, sleeping, and hunting. For example, artificial lights can confuse female sea turtles, discouraging them from nesting on bright coastal beaches. It can also disorient hatchlings, causing them to crawl towards cities instead of the ocean, resulting in millions of deaths annually.

Nocturnal animals, such as bats, raccoons, coyotes, deer, and moose, are particularly affected by light pollution. They experience a decline in reproduction and face challenges in foraging for food. Additionally, predators that typically hunt under the cover of darkness can more easily spot these nocturnal creatures, leading to increased mortality rates.

Altered Ecological Dynamics

Light pollution also alters ecological dynamics by disrupting the natural diurnal patterns of light and dark. This disruption can confuse the migratory patterns of animals, alter competitive interactions, change predator-prey relationships, and cause physiological harm to both plants and animals.

Health Risks

Light pollution poses health risks to humans as well. It can suppress melatonin production, leading to sleep disorders, increased headaches, worker fatigue, stress, and anxiety. There are also potential links between light pollution and certain types of cancer, as well as ties to obesity due to lack of sleep.

Energy Consumption and Air Pollution

Furthermore, light pollution contributes to increased energy consumption and air pollution. Lighting accounts for at least one-fourth of all electricity consumption worldwide, leading to higher carbon emissions and other harmful gases.

In summary, light pollution has far-reaching consequences for the environment, impacting plants, animals, and human health, while also contributing to energy wastage and air pollution. Addressing light pollution through responsible lighting practices can help mitigate these negative effects and restore the natural balance of ecosystems.

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