Light pollution
Light pollution is the alteration of the natural patterns of light and dark in ecosystems, resulting from artificial lighting. In a descriptive sense, light pollution occurs when artificial light is used in a poor or excessive way, especially at night, causing negative effects in the environment and the view of the night sky. Light pollution doesn't just negatively affect human health, but also the plants and animals that live within the wide surrounding regions affected by artificial lighting. Light pollution can be understood not only as a phenomenon resulting from a specific source or kind of pollution, but also as a contributor to the wider, collective impact of various sources of pollution.
Although this type of pollution can exist throughout the day, its effects are magnified during the night with the contrast of the sky's darkness. It has been estimated that 83% of the world's people live under light-polluted skies and that 23% of the world's land area is affected by skyglow.
The area affected by artificial illumination continues to increase. A major side effect of urbanization, light pollution is blamed for compromising health, disrupting ecosystems, and spoiling aesthetic environments. Studies show that urban areas are more at risk. Globally, it has increased by at least 49% from 1992 to 2017.
Light pollution is caused by inefficient or unnecessary use of artificial light. Specific categories of light pollution include light trespass, over-illumination, glare, light clutter, and skyglow. A single offending light source often falls into more than one of these categories.
Solutions to light pollution are often steps like adjusting light fixtures or using more appropriate light bulbs. Further remediation can be done with more efforts to educate the public in order to push legislative change. However, because it is a man-made phenomenon, addressing its impacts on humans and the environment has political, social, and economic considerations.
Definitions
Light pollution is the presence of artificial light in otherwise dark conditions.The term is most commonly used in relation to in the outdoor environment and surrounding, but is also used to refer to artificial light indoors. Adverse consequences are multiple; some of them may not be known yet. Light pollution makes it harder for people in cities that use excessive artificial light, and like other pollutants it can harm our environment. Light pollution is a side-effect of industrial civilization. Its sources 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 like Tehran and Cairo, but even relatively small amounts of light can be noticed and create problems. Awareness of the harmful effects of light pollution began in the second half of the 19th century, but efforts to address its effects did not begin until the 1950s. In the 1980s a global dark-sky movement emerged with the founding of the International Dark-Sky Association. There are now such educational and advocacy organizations in many countries worldwide.
About 83% of people, including 99% of Europeans and Americans, live under light-polluted skies that are more than 10% brighter than natural darkness. 80% of North Americans cannot see the Milky Way galaxy.
Types
Light trespass
Light trespass occurs when unwanted light enters one's property. A common light trespass problem occurs when a strong light enters the window of one's home from the outside, causing problems such as sleep deprivation. A number of cities in the U.S. have developed standards for outdoor lighting to protect the rights of their citizens against light trespass.The Dark-Sky Association was started to reduce the light going up into the sky which reduces the visibility of stars. This is any light that is emitted more than 90° above nadir. By limiting light at this 90° mark they have also reduced the light output in the 80–90° range which creates most of the light trespass issues.
U.S. federal agencies may also enforce standards and process complaints within their areas of jurisdiction. For instance, in the case of light trespass by white strobe lighting from communication towers in excess of FAA minimum lighting requirements the Federal Communications Commission maintains an Antenna Structure Registration database information which citizens may use to identify offending structures and provides a mechanism for processing citizen inquiries and complaints. The U.S. Green Building Council has also incorporated a credit for reducing the amount of light trespass and sky glow into their environmentally friendly building standard known as LEED.
Light trespass can be reduced by selecting light fixtures that limit the amount of light emitted more than 80° above the nadir. The IESNA definitions include full cutoff, cutoff, and semi-cutoff.
Over-illumination
Over-illumination is the excessive and unnecessary use of light.A large and overabundant amount of electricity is required to support light consumption in the United States. U.S homes consumed 81 billion kilowatt hours of electricity for lighting in 2020 according to the U.S. Energy Information Administration. Additionally, the EIA reported that 208 billion kWh and 53 billion kWh of electricity were used for commercial and manufacturing buildings respectively in 2018.
Light use is not excessive in all developed countries. Amongst developed countries there are large variations in patterns of light use. American cities emit three to five times more light to space per capita compared to German cities.
Over-illumination stems from several factors:
- Consensus-based standards or norms that are not based on vision science;
- The common misconception that increased illumination equals increased safety despite it having no proven effect and may worsen the problem;
- Improper design, by specifying higher levels of light than needed for a given visual task;
- Incorrect choice of fixtures or light bulbs, which do not direct light into areas as needed;
- Improper selection of hardware to utilize more energy than needed to accomplish the lighting task;
- Incomplete training of building managers and occupants to use lighting systems efficiently;
- Inadequate lighting maintenance resulting in increased stray light and energy costs;
- "Daylight lighting" demanded by citizens to reduce crime or by shop owners to attract customers;
- Substitution of old lamps with more efficient LEDs using the same electrical power; and
- Indirect lighting techniques, such as illuminating a vertical wall to bounce light onto the ground.
- Institutions who illuminate their buildings not to improve navigation, but "to show that its empire is inescapable".
- Lighting less for the benefit of seeing at night, and more for institutions to push working hours beyond natural daylight hours. An economic and financial gain as opposed to a necessity.
In certain cases, an over-illumination lighting technique may be needed. For example, indirect lighting is often used to obtain a "softer" look, since hard direct lighting is generally found less desirable for certain surfaces, such as skin. The indirect lighting method is perceived as cozier and suits bars, restaurants, and living quarters. It is also possible to block the direct lighting effect by adding softening filters or other solutions, though intensity will be reduced.
Glare
Glare can be categorized into different types. One such classification is described in a book by Bob Mizon, coordinator for the British Astronomical Association's Campaign for Dark Skies, as follows:- Blinding glare describes effects such as that caused by staring into the Sun. It is completely blinding and leaves temporary or permanent vision deficiencies.
- Disability glare describes effects such as being blinded by oncoming car lights, or light scattering in fog or in the eye, reducing contrast, as well as reflections from print and other dark areas that render them bright, with a significant reduction in sight capabilities.
- Discomfort glare does not typically cause a dangerous situation in itself, though it is annoying and irritating at best. It can potentially cause fatigue if experienced over extended periods.
The blinding effect is caused in large part by reduced contrast due to light scattering in the eye by excessive brightness, or to the reflection of light from dark areas in the field of vision, with luminance similar to the background luminance. This kind of glare is a particular instance of disability glare, called veiling glare.