This time exposure photo of New York City at night shows sky glow, one form of light pollution. In Photography, exposure is the total amount of Light allowed to fall on the photographic medium ( Photographic film or Image sensor) during the The City of New York Skyglow (or sky glow) is a kind of Light pollution, visible by the "glowing" effect seen in the skies over many cities and towns as a dome of light

Light pollution, also known as photopollution or luminous pollution, is excess or obtrusive light created by humans. Pollution is the introduction of contaminants into an environment that causes instability disorder harm or discomfort to the physical systems or living organisms they are in Air pollution is the human introduction into the atmosphere of Chemicals Particulate matter, or Biological materials that cause harm or discomfort Acid rain is Rain or any other form of precipitation that is unusually Acidic It has harmful effects on plants aquatic animals and infastructure The Air Quality Index ( AQI) is a standardized indicator of the Air Quality in a given location Atmospheric dispersion modeling is the mathematical simulation of how air pollutants disperse in the ambient atmosphere. The haloalkanes (also known as halogenoalkanes or alkyl halides) are a group of Chemical compounds consisting of Alkanes such as Methane Global dimming is the gradual reduction in the amount of global direct Irradiance at the Earth 's surface that was observed for several decades after the start of systematic Global warming is the increase in the average measured temperature of the Haze is traditionally an atmospheric phenomenon where dust smoke and other dry particles obscure the clarity of the sky Indoor Air Quality (IAQ deals with the content of interior air that could affect health and comfort of building occupants Ozone depletion describes two distinct but related observations a slow steady decline of about 4 percent per decade in the total amount of Ozone in Earth's Particulates, alternatively referred to as particulate matter (PM or fine particles, are tiny particles of solid or liquid suspended in a gas Smog is a kind of Air pollution; the word "smog" is a Portmanteau of Smoke and Fog. Water pollution is the contamination of Water bodies such as Lakes Rivers Oceans and Groundwater caused by human activities Eutrophication is an increase in chemical Nutrients -- typically compounds containing Nitrogen or Phosphorus -- in an Ecosystem, and may occur For other uses of the term "hypoxia" see Hypoxia. Hypoxia or oxygen depletion is a phenomenon that occurs in aquatic environments Marine pollution is the harmful effect caused by the entry into the ocean of chemicals particles, or Plastic debris. For the fictional character see Oil Slick (Transformers. An oil spill is the release of a Liquid Petroleum Hydrocarbon into Ship pollution is the pollution of air and Water by Shipping. Surface runoff is a term used to describe when soil is infiltrated to full capacity and excess Water, from Rain, Snowmelt, or other sources flows Thermal pollution is a Temperature change in natural bodies of water caused by human influence Distinguish from Wastwater (a lake in the Lake District in northwest England Waterborne diseases are caused by Pathogenic Microorganisms which are directly transmitted when contaminated Drinking water is consumed Water quality is the physical chemical and biological characteristics of Water in relationship to a set of standards Water stagnation occurs when Water stops flowing Stagnant water can be a major Environmental hazard. Soil contamination is caused by the presence of man-made chemicals or other alteration in the natural soil environment Bioremediation can be defined as any process that uses Microorganisms Fungi, green plants or their Enzymes to return the natural environment altered A herbicide is used to kill unwanted Plants Selective herbicides kill specific targets while leaving the desired Crop relatively unharmed A pesticide is a substance or mixture of substances used to kill a pest. Radioactive contamination is the uncontrolled distribution of radioactive material in a given environment Actinides in the environment refer to the sources environmental behaviour and effects of Actinides in the environment. Environmental Radioactivity is the study of radioactive materials in the Human environment. Fission products are the atomic fragments left after a large nucleus fissions. Fallout is the residual radiation hazard from a Nuclear explosion, so named because it "falls out" of the atmosphere into which it is spread during the explosion Plutonium in the environment is an article which is part of the Actinides in the environment series Radiation poisoning, also called " radiation sickness " or a " creeping dose " is a form of damage to organ tissue due to excessive exposure to This is a subpage of Environmental radioactivity. Radium Radium in quack medicine See the story of Eben Byers for details of one very nasty case Uranium in the environment, this page is about the Science of Uranium in the environment and in animals (including humans Introduced species|Weed Invasive species is a phrase with several definitions Noise pollution (or environmental noise) is displeasing human- or machine-created sound that disrupts the activity or balance of human or animal life Radio spectrum pollution is the straying of waves in the radio and Electromagnetic spectrums outside their allocations that cause problems for some activities Visual pollution is the term given to unattractive or unnatural (human-made visual elements of a vista a Landscape, or any other thing that a person might not want to For other similarly-named agreements see Montreal Convention (disambiguation. Protocol to the 1979 Convention on Long-Range Transboundary Air Pollution Concerning the Control of Emissions of Nitrogen Oxides or Their Transboundary Fluxes, opened for signature on The Kyoto Protocol is a protocol to the international Framework Convention on Climate Change with the objective of reducing Greenhouse gases in an effort The Convention on Long-Range Transboundary Air Pollution, often abbreviated as Air Pollution or CLRTAP, is intended to protect the human environment against Air This is a list of environmental organizations. See also Environmental organization Intergovernmental organizations International organizations The Department for Environment Food and Rural Affairs ( Defra) is the United Kingdom government department responsible for environmental protection The Global Atmosphere Watch (GAW is a worldwide system established by the World Meteorological Organization a United Nations agency to monitor trends in the Greenpeace, originally known as the Greenpeace Foundation, was founded in Vancouver, British Columbia, Canada in 1972 The National Ambient Air Quality Standards (NAAQS are standards established by the United States Environmental Protection Agency that apply for outdoor Air Environmental science is the study of interactions among physical chemical and biological components of the environment. See also Nature The natural environment, commonly referred to simply as the environment, is a terminology that is comprised of all living and Light, or visible light, is Electromagnetic radiation of a Wavelength that is visible to the Human eye (about 400–700 Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus Among other effects, and like any other form of pollution, it disrupts ecosystems, can cause adverse health effects, obscures the stars for city dwellers, and interferes with astronomical observatories. An ecosystem is a natural unit consisting of all plants animals and micro-organisms( Biotic factors in an area functioning together with all of the non-living physical ( A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth A city is an Urban area with a large Population and a particular Administrative, Legal, or Historical status Astronomy (from the Greek words astron (ἄστρον "star" and nomos (νόμος "law" is the scientific study An observatory is a location used for observing terrestrial and/or celestial events Light pollution can be construed to fall into two main branches: annoying light that intrudes on an otherwise natural or low light setting and excessive light, generally indoors, that leads to worker discomfort and adverse health effects. Since the early 1980s, a global dark-sky movement has emerged, with concerned people campaigning to reduce the amount of light pollution. The dark-sky movement is a campaign by people who want to reduce Light pollution so people can see the stars to reduce the effects of unnatural lighting on the environment

Light pollution is a side effect of industrial civilization. is a process of social and economic change whereby a human group is transformed from a Pre-industrial society into an industrial one Its sources include building exterior and interior lighting, advertising, commercial properties, offices, factories, streetlights, and illuminated sporting venues. Lighting includes both artificial Light sources such as lamps and natural illumination of interiors from Daylight. Advertising is a form of Communication that typically attempts to persuade potential Customers to Purchase or to consume more of a particular Brand A business (also called firm or an enterprise) is a legally recognized organizational entity designed to provide goods and/or services to An office is generally a room or other area in which people work, but may also denote a position within an Organization with specific duties attached A factory (previously manufactory) or manufacturing plant is an industrial Building where workers manufacture goods A street light, lamppost, street lamp, light standard or lamp standard, is a raised source of Light on the edge of a Road A modern stadium (plural stadiums or stadia in English is a place or venue for (mostly outdoor Sports Concerts or other events consisting It is most severe in highly industrialized, densely populated areas of North America, Europe, and Japan and in major cities in the Middle East and North Africa like Cairo, but even relatively small amounts of light can be noticed and create problems. For a topic outline on this subject see List of basic Japan topics. The Middle East is a Subcontinent with no clear boundaries often used as a synonym to Near East, in opposition to Far East. North Africa or Northern Africa is the Northernmost Region of the African Continent, separated by the Sahara from Sub-Saharan Cairo () which means "the Vanquisher" or "the Triumphant" is the capital and largest city of Egypt. Like other forms of pollution, such as air, water and noise pollution, light pollution causes damage to the environment. Air pollution is the human introduction into the atmosphere of Chemicals Particulate matter, or Biological materials that cause harm or discomfort Water pollution is the contamination of Water bodies such as Lakes Rivers Oceans and Groundwater caused by human activities Noise pollution (or environmental noise) is displeasing human- or machine-created sound that disrupts the activity or balance of human or animal life

With recent advances in private spaceflight, the prospect of space-based orbiting billboards appearing in the near future has provoked concern that such objects may become another form of light pollution. Private spaceflight is flight above Earth Altitude conducted by and paid for by an entity other than a government With this in mind, the United States Federal Aviation Administration sought permission, in May 2005, to enforce a law prohibiting "obtrusive" advertising in earth orbit. The United States of America —commonly referred to as the The Federal Aviation Administration ( FAA) is an agency of the United States Department of Transportation with authority to regulate and oversee all aspects of ^[1][2] Similar intentions are yet to be expressed by authorities in most other countries.

Impact on energy usage

Energy conservation advocates contend that light pollution must be addressed by changing the habits of society, so that lighting is used more efficiently, with less waste and less creation of unwanted or unneeded illumination. Energy conservation is the practice of decreasing the quantity of energy used See also Habit (psychology In Psychology, habituation is the psychological process in humans and animals in which there is a decrease in behavioral Luminous efficacy is a property of Light sources which indicates what portion of the emitted Electromagnetic radiation is usable for human vision. The case against light pollution is strengthened by a range of studies on health effects, suggesting that excess light may induce loss in visual acuity, hypertension, headaches and increased incidence of carcinoma. Eye examination Visual acuity (VA is acuteness or clearness of vision, especially form vision which is dependent on the sharpness of the retinal focus within the Hypertension, also referred to as high blood pressure, HTN or HPN, is a medical condition in which the Blood pressure is chronically elevated A headache ( cephalalgia in medical terminology is a condition of pain in the Head; sometimes Neck or upper back pain may also be interpreted A carcinoma is any Malignant Cancer that arises from epithelial cells. Several industry groups also recognize light pollution as an important issue. For example, the Institution of Lighting Engineers in the United Kingdom provides its members information about light pollution, the problems it causes, and how to reduce its impact. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located ^[3]

Since not everyone is irritated by the same lighting sources, it is common for one person's light "pollution" to be light that is desirable for another. Irritation or exacerbation, in Biology and Physiology, is a state of Inflammation or painful reaction to Allergy or cell-lining damage One example of this is found in advertising, when an advertiser wishes for particular lights to be bright and visible, even though others find them annoying. Advertising is a form of Communication that typically attempts to persuade potential Customers to Purchase or to consume more of a particular Brand Other types of light pollution are more certain. For instance, light that accidentally crosses a property boundary and annoys a neighbor is generally wasted and pollutive light. Property is any physical or virtual entity that is owned by an individual

Disputes are still common when deciding appropriate action, and differences in opinion over what light is considered reasonable, and who should be responsible, mean that negotiation must sometimes take place between parties. For Wikipedia's negotiation policy see WikipediaNegotiation. For other uses see Negotiation (disambiguation. Where objective measurement is desired, light levels can be quantified by field measurement or mathematical modeling, with results typically displayed as an isophote map or light contour map. Note The term model has a different meaning in Model theory, a branch of Mathematical logic. A contour line (also Level set, isopleth, isoline, isogram or isarithm) of a function of two Authorities have also taken a variety of measures for dealing with light pollution, depending on the interests, beliefs and understandings of the society involved. Measures range from doing nothing at all, to implementing strict laws and regulations about how lights may be installed and used. This article is for the legal term For regulation of genes see Regulation of gene expression.

Types of light pollution

Example of a light pollution source using a broad spectrum metal halide lamp pointing upward. Metal halide lamps, a member of the High-intensity discharge (HID family of lamps produce high light output for their size making them a compact powerful and efficient Location: Uniqema Gouda the Netherlands

Light pollution is a broad term that refers to multiple problems, all of which are caused by inefficient, unappealing, or (arguably) unnecessary use of artificial light. Gouda (population 71797 in 2004 is a city and municipality in the western Netherlands, in the province of South Holland. Specific categories of light pollution include light trespass, over-illumination, glare, clutter, and sky glow. A single offending light source often falls into more than one of these categories.

Light trespass

Light trespass occurs when unwanted light enters one's property, for instance, by shining over a neighbor's fence. A common light trespass problem occurs when a strong light enters the window of one's home from outside, causing problems such as sleep deprivation or the blocking of an evening view. Sleep deprivation is a general lack of the necessary amount of Sleep.

Light is particularly problematic for amateur astronomers, whose ability to observe the night sky from their property is likely to be inhibited by any stray light from nearby. Amateur astronomy, a subset of Astronomy, is a Hobby whose participants enjoy studying and observing celestial objects Most major optical astronomical observatories are surrounded by zones of strictly-enforced restrictions on light emissions.

A number of cities in the U. S. have developed standards for outdoor lighting to protect the rights of their citizens against light trespass. To assist them, the International Dark-Sky Association has developed a set of model lighting ordinances. The International Dark-Sky Association ( IDA) is a US-based Non-profit organization incorporated in 1988 by founding members including an astronomer a medical ^[4] U. S. federal agencies may also enforce standards and process complaints within their areas of jursidiction. For instance, in the case of light trespass by white strobe lighting from communication towers in excess of FAA minimum lighting requirements the FCC maintains a database of Antenna Structure Registration information which citizens may use to identify offending structures and provides a mechanism for processing consumer inquiries and complaints.

Over-illumination

Main article: Over-illumination

Office building illuminated by high pressure sodium (HPS) lamps shining upward, of which much light goes into the sky and neighboring apartment blocks and causes light pollution. The Federal Aviation Administration ( FAA) is an agency of the United States Department of Transportation with authority to regulate and oversee all aspects of Over-illumination is the presence of lighting intensity ( Illuminance) beyond that required for a specified activity A sodium vapor lamp is a Gas discharge lamp which uses Sodium in an excited state to produce Light Location: Nijmegen, the Netherlands

Composite satellite image of the Earth at night. Nijmegen (ˈnɛɪmeɣən) (obsolete spellings Nijmwegen Nymegen Nieumeghen &mdash Nimwegen in local dialect and in German, Nimègue in French Satellite imagery consists of photographs of Earth or other planets made by means of Artificial satellites. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001

Over-illumination is the excessive use of light. Specifically within the United States, over-illumination is responsible for approximately two million barrels of oil per day in energy wasted. The United States of America —commonly referred to as the This is based upon U. S. consumption of equivalent of 50 million barrels per day (7,900,000 m³/d) of petroleum. ^[5] It is further noted in the same U. S. Department of Energy source that over 30 percent of all energy is consumed by commercial, industrial and residential sectors. For other uses of this term see Industry (disambiguation An industry (from Latin industrius, "diligent industrious" Within a urban area there is a tendency for land uses to Aggregate. Energy audits of existing buildings demonstrate that the lighting component of residential, commercial and industrial uses consumes about 20 to 40 percent of those land uses, variable with region and land use. (Residential use lighting consumes only 10 to 30 percent of the energy bill while commercial buildings major use is lighting. ^[6]) Thus lighting energy accounts for about four or five million barrels of oil (equivalent) per day. Again energy audit data demonstrates that about 30 to 60 percent of energy consumed in lighting is unneeded or gratuitous. ^[7]

An alternative calculation starts with the fact that commercial building lighting consumes in excess of 81. 68 terawatts (1999 data) of electricity,^[8] according to the U. S. DOE. Thus commercial lighting alone consumes about four to five million barrels per day (equivalent) of petroleum, in line with the alternate rationale above to estimate U. S. lighting energy consumption.

Over-illumination stems from several factors:

• Not using timers, occupancy sensors or other controls to extinguish lighting when not needed
• Improper design, especially of workplace spaces, by specifying higher levels of light than needed for a given 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

Most of these issues can be readily corrected with available, inexpensive technology; however, there is considerable inertia in the field of lighting design and with landlord/tenant practices that create barriers to rapid correction of these matters. Motion detection is the action of sensing physical movement in a given area Lighting includes both artificial Light sources such as lamps and natural illumination of interiors from Daylight. An office is generally a room or other area in which people work, but may also denote a position within an Organization with specific duties attached A light fixture is an electrical device used to create artificial light or illumination A lamp is a replaceable component such as an Incandescent light bulb, which is designed to produce Light from Electricity. Most importantly public awareness would need to improve for industrialized countries to realize the large payoff in reducing over-illumination.

Glare

Glare is often the result of excessive contrast between bright and dark areas in the field of view. For example, glare can be associated with directly viewing the filament of an unshielded or badly shielded light. Light shining into the eyes of pedestrians and drivers can obscure night vision for up to an hour after exposure. Night vision is the ability to see in a dark environment Whether by biological or technological means night vision is made possible by a combination of two approaches sufficient Caused by high contrast between light and dark areas, glare can also make it difficult for the human eye to adjust to the differences in brightness. Eyes are organs that detect Light, and send signals along the Optic nerve to the visual areas of the brain Glare is particularly an issue in road safety, as bright and/or badly shielded lights around roads may partially blind drivers or pedestrians unexpectedly, and contribute to accidents.

Glare can also result in reduced contrast, due to light scattering in the eye by excessive brightness, or to 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.

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. ^[9] According to this classification:

• Blinding Glare describes effects such as that caused by staring into the Sun. The Sun (Sol is the Star at the center of the Solar System. It is completely blinding and leaves temporary or permanent vision deficiencies.
• Disability Glare describes effects such as being blinded by an oncoming cars lights, or light scattering in fog or in the eye reduces contrast, as well as reflections from print and other dark areas that render them bright, with significant reduction in sight capabilities.
• Discomfort Glare does not typically cause a dangerous situation in itself, and is annoying and irritating at best. It can potentially cause fatigue if experienced over extended periods.

Clutter

Clutter refers to excessive groupings of lights. Groupings of lights may generate confusion, distract from obstacles (including those that they may be intended to illuminate), and potentially cause accidents. An accident is a specific identifiable unexpected unusual and unintended external event which occurs in a particular time and place without apparent or deliberate Clutter is particularly noticeable on roads where the street lights are badly designed, or where brightly lit advertising surrounds the roadways. A road is an identifiable route, way or path between two or more places. Depending on the motives of the person or organization who installed the lights, their placement and design may even be intended to distract drivers, and can contribute to accidents. Driving is the controlled operation of a land Vehicle, usually a Motor vehicle such as a Truck or a car. Clutter may also present a hazard in the aviation environment if aviation safety lighting must compete for pilot attention with non-relevant lighting. Aviation refers to activities involving man-made flying devices ( Aircraft) including the people organizations and regulatory bodies involved with them ^[10] For instance, runway lighting may be confused with an array of suburban commercial lighting and aircraft collision avoidance lights may be confused with ground lights.

Sky glow

Mexico City at night, with a brightly illuminated sky. Mexico City (in Spanish: Ciudad de México, México DF, México or simply Méjico) is the Capital city of Mexico

Main article: Sky glow

Sky glow refers to the "glow" effect that can be seen over populated areas. Skyglow (or sky glow) is a kind of Light pollution, visible by the "glowing" effect seen in the skies over many cities and towns as a dome of light It is the combination of all light reflected from what it has illuminated escaping up into the sky and from all of the badly directed light in that area that also escapes into the sky, being scattered (redirected) by the atmosphere back toward the ground. This scattering is very strongly related to the wavelength of the light when the air is very clear (with very little aerosols). Technically an aerosol is a suspension of fine solid particles or liquid droplets in a gas Rayleigh scattering dominates in such clear air, making the sky appear blue in the daytime. Rayleigh scattering (named after Lord Rayleigh) is the elastic Scattering of Light or other electromagnetic radiation by particles much smaller When there is significant aerosol (typical of most modern polluted conditions), the scattered light has less dependence on wavelength, making a whiter daytime sky. Technically an aerosol is a suspension of fine solid particles or liquid droplets in a gas Because of this Rayleigh effect, and because of the eye's increased sensitivity to white or blue-rich light sources when adapted to very low light levels (see Purkinje effect), white or blue-rich light contributes significantly more to sky-glow than an equal amount of yellow light. The Purkinje effect (sometimes called the Purkinje shift, or dark adaptation and named after the Czech Anatomist Jan Evangelista Purkyně Sky glow is of particular irritation to astronomers, because it reduces contrast in the night sky to the extent where it may even become impossible to see any but the brightest stars.

The Bortle Dark-Sky Scale, originally published in Sky & Telescope magazine,^[11] is sometimes used to quantify sky glow and general sky clarity. The Bortle Dark-Sky Scale is a nine-level numeric measure of the night sky brightness of a particular location Sky & Telescope (S&T is an American monthly Magazine covering all aspects of Amateur astronomy, including current events in The Bortle Scale rates the darkness of the sky and the visibility of night sky phenomena such as the gegenschein and the zodiacal band, easily masked by sky glow, on a scale of one to nine, providing a detailed description of each step on the scale. Gegenschein ( very roughy like GAY-guhn-shine German for "counter shine" is a faint brightening of the night sky in the region of the Antisolar The zodiacal light is a faint roughly triangular whitish glow seen in the night sky which appears to extend up from the vicinity of the Sun along the Ecliptic

Measurement of light pollution and global effects

False colors show various intensities of radiation — both direct and indirect — from artificial light sources that reach space (Image credit: P. Cinzano)

Measuring the effect of sky glow on a global scale is a complex procedure. The natural atmosphere is not completely dark, even in the absence of terrestrial sources of light. This is caused by two main sources: airglow and scattered light.

At high altitudes, primarily above the mesosphere, UV radiation from the sun is so intense that ionization occurs. This article is about the atmospheric mesosphere for the Earth's mantle see Mesosphere (mantle. When these ions collide with electrically neutral particles they recombine and emit photons in the process, causing airglow. The airglow is the very weak emission of light by the Earth's atmosphere; as a result the night sky is never completely dark The degree of ionization is sufficiently large to allow a constant emission of radiation even during the night when the upper atmosphere is in the earth's shadow.

Apart from emitting light, the sky also scatters incoming light, primarily from distant stars and the Milky Way, but also sunlight that is reflected and backscattered from interplanetary dust particles (the so-called Zodiacal light). The zodiacal light is a faint roughly triangular whitish glow seen in the night sky which appears to extend up from the vicinity of the Sun along the Ecliptic

The amount of airglow and zodiacal light is quite variable but given optimal conditions the darkest possible sky has a brightness of about 22 magnitude/square arcsecond. If a full moon is present, the sky brightness increases to 18 magnitude/sq. This article is primarily about the brightness of the night sky arcsecond, 40 times brighter than the darkest sky. In densely populated areas a sky brightness of 17 magnitude/sq. arcsecond is not uncommon, or as much as 100 times brighter than is natural.

To precisely measure how bright the sky gets, night time satellite imagery of the earth is used as raw input for the number and intensity of light sources. These are put into a physical model^[12] of scattering due to air molecules and aerosoles to calculate cumulative sky brightness. Maps that show the enhanced sky brightness have been prepared for the entire world. ^[13]

Inspection of the area surrounding Madrid reveals that the effects of light pollution caused by a single large conglomeration can be felt up to 100 km away from the center. Global effects of light pollution are also made obvious. The entire area consisting of southern England, Netherlands, Belgium, west Germany, and northern France have a sky brightness of at least 2 to 4 times above normal (see above right). The only place in continental Europe where the sky can attain its natural darkness is in northern Scandinavia.

In North America the situation is comparable. From the east coast to west Texas up to the Canadian border there is very significant global light pollution.

Consequences of light pollution

Energy waste

Lighting is responsible for one fourth of all energy consumed worldwide, and case studies have shown that several forms of over-illumination constitute energy wastage including non-beneficial upward direction of night-time lighting. Lighting includes both artificial Light sources such as lamps and natural illumination of interiors from Daylight. Over-illumination is the presence of lighting intensity ( Illuminance) beyond that required for a specified activity

Effects on human health and psychology

Medical research on the effects of excessive light on the human body suggests that a variety of adverse health effects may be caused by light pollution or excessive light exposure, and some lighting design textbooks^[14] use human health as an explicit criterion for proper interior lighting. Health is a state of complete physical mental and social well-being and not merely the absence of disease or infirmity Health effects of over-illumination or improper spectral composition of light may include: increased headache incidence, worker fatigue, medically defined stress, decrease in sexual function and increase in anxiety. A headache ( cephalalgia in medical terminology is a condition of pain in the Head; sometimes Neck or upper back pain may also be interpreted Generally speaking human sexuality is how people experience and express themselves as sexual beings ^{[15][16][17][18]}

Common levels of fluorescent lighting in offices are sufficient to elevate blood pressure by about eight points. There is some evidence that lengthy daily exposure to moderately high lighting leads to diminished sexual performance. Specifically within the USA, there is evidence that levels of light in most office environments lead to increased stress as well as increased worker errors. ^[19][20] However, such high interior lighting levels are not typical outside North America.

Several published studies also suggest a link between exposure to light at night and risk of breast cancer, due to suppression of the normal nocturnal production of melatonin. Breast cancer is a Cancer that starts in the cells of the Breast in women and men Melatonin is a naturally occurring Hormone found in most animals including humans and some other living organisms including Algae. ^[21][22]

In 1978 Cohen et al proposed that reduced production of the hormone melatonin might increase the risk of breast cancer and citing "environmental lighting" as a possible causal factor. ^[23]

Researchers at the National Cancer Institute (NCI) and National Institute of Environmental Health Sciences have concluded a study that suggests that artificial light during the night can be a factor for breast cancer. The National Cancer Institute (NCI is part of the United States Federal government's National Institutes of Health. The National Institute of Environmental Health Sciences (NIEHS is one of 27 Institutes and Centers of the National Institutes of Health (NIHwhich is a component of the Department ^[24]

In 2007, "shiftwork that involves circadian disruption" was listed as a probable carcinogen by the World Health Organization's International Agency for Research on Cancer. (IARC Press release No. 180). ^[25] Multiple studies have documented a link between night shift work and the increased incidence of breast cancer. ^{[26][27][28][29]}

A good review of current knowledge of the health consequences of exposure to artificial light at night and an explanation of the causal mechanisms has been published in the Journal of Pineal Research in 2007. ^[30]

Disruption of ecosystems

Life exists with natural patterns of light and dark, so disruption of those patterns influences many aspects of animal behavior. ^[31] Light pollution can confuse animal navigation, alter competitive interactions, change predator-prey relations, and influence animal physiology.

Studies suggest that light pollution around lakes prevents zooplankton, such as Daphnia, from eating surface algae, helping cause algal blooms that can kill off the lakes' plants and lower water quality. Daphnia are small Planktonic Crustaceans between.2 and 5  mm in length Algae ( sing. alga are a large and diverse group of simple typically Autotrophic organisms ranging from Unicellular to Multicellular forms An algal bloom is a rapid increase in the population of Algae in an aquatic system ^[32] Light pollution may also affect ecosystems in other ways. For example, Lepidopterists and entomologists have documented that night-time light may interfere with the ability of moths and other nocturnal insects to navigate. A lepidopterist is a person who catches and collects studies or simply observes (see Butterfly watching) lepidopterans, members of an order encompassing Entomology (from Greek grc ἔντομος entomos, "that which is cut in pieces or engraved/segmented" hence "insect" and grc -λογία ^[33] Night blooming flowers that depend on moths for pollination may be affected by night lighting, as there is no replacement pollinator that would not be affected by the artificial light. A flower, also known as a bloom or Blossom, is the reproductive structure found in Flowering plants (plants of the division Magnoliophyta, also Pollination in angiosperms and Gymnosperms is the process that transfers pollen grains, which contain the male Gametes (sperm to where the female A pollinator is the biotic agent ( vector) that moves Pollen from the male Anthers of a Flower to the female stigma of a flower to accomplish This can lead to species decline of plants that are unable to reproduce, and change an area's longterm ecology. Plants are living Organisms belonging to the kingdom Plantae. Ecology (from Greek grc οἶκος oikos, "house(hold" and grc -λογία -logia) is the scientific study of

Migrating birds can be disoriented by lights on tall structures. Estimates by the U. S. Fish and Wildlife Service of the number of birds killed after being attracted to tall towers range from 4-5 million per year to an order of magnitude higher. ^[34] The Fatal Light Awareness Program (FLAP) works with building owners in Toronto, Canada and other cities to reduce mortality of birds by turning out lights during migration periods. Toronto (təˈrɒntoʊ colloquially pronounced or) is the largest city in Canada and is the provincial capital of Ontario

Other well-known casualties of light pollution are sea turtle hatchlings emerging from nests on beaches. Sea turtles ( Superfamily Chelonioidea) are Turtles found in all the world's oceans except the Arctic Ocean. It is a common misconception that hatchling sea turtles are attracted to the moon. They are not; rather, they find the ocean by moving away from the dark silhouette of dunes and their vegetation, a behavior with which artificial lights interfere. ^[35] Juvenile seabirds may also be disoriented by lights as they leave their nests and fly out to sea.

Nocturnal frogs and salamanders are also affected by light pollution. Since they are nocturnal, they wake up when there is no light. Light pollution may cause salamanders to emerge from concealment later, giving them less time to mate and reproduce.

A book that assembles various research on the subject was released in 2005. ^[36]

Loss of safety

It is generally agreed that many people require light to feel safe at night, but campaigners for the reduction of light pollution often claim that badly or inappropriately installed lighting can lead to a reduction in safety if measured objectively, and that at the very least, it is wrong to assume that simply increasing light at night will lead to improved safety.

The International Dark-Sky Association claims there are no good scientific studies that convincingly show a relationship between lighting and crime. Furthermore, the association claims that badly installed artificial lights can create a deeper contrast of shadows in which criminals might hide. ^[37] The New England Light Pollution Advisory Group claims that some light emitted by some fixtures can be a significant hazard to motorists, pedestrians, and bicyclists due to their scattering of light and glare. ^[38]

The specific effects of outdoor lighting on safety are still a topic of debate, and formal research in the area is not well established.

Effect on astronomy

Skyglow reduces the contrast between stars and galaxies in the sky and the sky itself, making it more difficult to detect fainter objects. This is one factor that has caused newer telescopes to be built in increasingly remote areas. A telescope is an instrument designed for the observation of remote objects and the collection of Electromagnetic radiation. Some astronomers use narrow-band "nebula filters" which only allow specific wavelengths of light commonly seen in nebulae, or broad-band "light pollution filters" which are designed to reduce (but not eliminate) the effects of light pollution by filtering out spectral lines commonly emitted by sodium- and mercury-vapor lamps, thus enhancing contrast and improving the view of dim objects such as galaxies and nebulae. A nebula (from Latin: "mist" pl nebulae or nebulæ, with ligature or nebulas) is an Interstellar cloud of A sodium vapor lamp is a Gas discharge lamp which uses Sodium in an excited state to produce Light A galaxy is a massive gravitationally bound system consisting of Stars an Interstellar medium of gas and dust, and Dark matter

Light trespass can impact observations when stray light enters the tube of the telescope from off-axis, and is reflected from surfaces other than the telescope's mirrors (if any) so that it eventually reaches the eyepiece, causing a glow across the field of view since it has not been focused. For the device for looking through a camera see Viewfinder. An eyepiece, or ocular lens, is a type of lens that is attached The field of view (also field of vision) is the angular extent of the observable world that is seen at any given moment The usual measures to reduce this glare, if reducing the light directly (e. g. by changing one's location or having the light turned off) is not an option, include flocking the telescope tube and accessories to reduce reflection, and putting a light shield (also known as a dew shield) on the telescope to reduce light entering from angles other than those near the target. Flocking is the process of depositing many small fiber particles (called "flock" onto a surface A dew shield is a device used to prevent Moisture or Condensation buildup on the lens of a Camera or Telescope collector during cool

Reducing light pollution

Reducing light pollution implies many things, such as reducing sky glow, reducing glare, reducing light trespass, and reducing clutter. The method for best reducing light pollution, therefore, depends on exactly what the problem is in any given instance. Possible solutions include:

• Utilizing light sources of minimum intensity necessary to accomplish the light's purpose.
• Turning lights off using a timer or occupancy sensor or manually when not needed.
• Improving lighting fixtures, so that they direct their light more accurately towards where it is needed, and with less side effects.
• Adjusting the type of lights used, so that the light waves emitted are those that are less likely to cause severe light pollution problems.
• Evaluating existing lighting plans, and re-designing some or all of the plans depending on whether existing light is actually needed.

Improving lighting fixtures

A flat-lens cobra luminaire, which is a full-cutoff fixture, may be effective in reducing light pollution. It ensures that light is only directed below the horizontal, which means less light is wasted through directing it outwards and upwards.

This drop-lens cobra luminaire allows light to escape sideways and upwards, where it may cause problems.

The use of full cutoff lighting fixtures, as much as possible, is advocated by most campaigners for the reduction of light pollution. It is also commonly recommended that lights be spaced appropriately for maximum efficiency, and that lamps within the fixtures not be overpowered.

A full cutoff fixture, when correctly installed, reduces the chance for light to escape above the plane of the horizontal. Light released above the horizontal may sometimes be lighting an intended target, but often serves no purpose. When it enters into the atmosphere, light contributes to sky glow. Some governments and organizations are now considering, or have already implemented, full cutoff fixtures in street lamps and stadium lighting.

The use of full cutoff fixtures may help to reduce sky glow by preventing light from escaping unnecessarily. Full cutoff typically reduces the visibility of the lamp and reflector within a luminarie, so the effects of glare may also be reduced. Campaigners also commonly argue that full cutoff fixtures are more efficient than other fixtures, since light that would otherwise have escaped into the atmosphere may instead be directed towards the ground. However, full cutoff fixtures may also trap more light in the fixture than other types of luminaires, corresponding to lower luminaire efficiency.

The use of full cutoff fixtures may allow for lower wattage lamps to be used in the fixtures, producing the same or sometimes a better effect, due to being more carefully controlled. In every lighting system, some sky glow also results from light reflected from the ground. This reflection can be reduced, however, by being careful to use only the lowest wattage necessary for the lamp, and setting spacing between lights appropriately. ^[39]

A common criticism of full cutoff lighting fixtures is that they are sometimes not as aesthetically pleasing to look at. This is most likely because historically there has not been a large market specifically for full cutoff fixtures, and because people typically like to see the source of illumination. Due to the specificity with their direction of light, full cutoff fixtures sometimes also require expertise to install for maximum effect.

The effectiveness of using full cutoff roadway lights to combat light pollution has also been called into question. According to computer simulations, luminaires with full cutoff distributions (as opposed to cutoff or semi cutoff, compared here) have to be closer together to meet the same light level, uniformity and glare requirements specified by the IESNA. The Illuminating Engineering Society of North America ( IESNA is a non-profit Learned society founded in New York City on January 10, 1906. ^{[40][41][42][43]} These simulations attempted to optimize the height and spacing of the lights while constraining the overall design to within the IESNA requirements, and then compared total uplight and energy consumption of different luminaire designs and powers. Cutoff designs paradoxically performed better than full cutoff designs. This indicates that, in roadway installations, over-illumination required by full cutoff fixtures may be more detrimental than direct uplight created by fewer cutoff fixtures. Therefore, existing systems could be improved more by reducing the number of luminaires than by switching to full cutoff designs.

Adjusting types of light sources

Several different types of light sources exist, each having different properties that affect their appropriateness for certain tasks, particularly efficiency and spectral power distribution. It is often the case that inappropriate light sources have been selected for a task, either due to ignorance or because more sophisticated light sources were unavailable at the time of installation. Therefore, badly chosen light sources often contribute unnecessarily to light pollution and energy waste. By re-assessing and changing the light sources used, it is often possible to reduce energy use and pollutive effects while simultaneously greatly improving efficiency and visibility.

Some types of light sources, in order of energy efficiency, are:

Many astronomers request that nearby communities use low pressure sodium lights as much as possible, because the principal wavelength emitted is comparably easy to work around or in rare cases filter out. The lumen (symbol lm) is the SI unit of Luminous flux, a measure of the perceived power of Light. The watt (symbol W) is the SI derived unit of power, equal to one Joule of energy per Second. A sodium vapor lamp is a Gas discharge lamp which uses Sodium in an excited state to produce Light A sodium vapor lamp is a Gas discharge lamp which uses Sodium in an excited state to produce Light Metal halide lamps, a member of the High-intensity discharge (HID family of lamps produce high light output for their size making them a compact powerful and efficient The incandescent light bulb, incandescent lamp or incandescent light globe is a source of electric Light that works by Incandescence, (a general ^[44] The low cost of operating sodium lights is another feature. In 1980, for example, San Jose, California, replaced all street lamps with low pressure sodium lamps, whose light is easier for nearby Lick Observatory to filter out. A sodium vapor lamp is a Gas discharge lamp which uses Sodium in an excited state to produce Light The Lick Observatory is an astronomical Observatory, owned and operated by the University of California. Similar programs are now in place in Arizona and Hawaii. The State of Arizona ( is a state located in the southwestern region of the United States. The State of Hawaii ( or həˈwaɪʔiː Hawaiian: Mokuāina o Hawaii) is a state in the United States located on an Archipelago in the

Disadvantages of low pressure sodium lighting are that fixtures must usually be larger than competing fixtures, and color cannot be distinguished — due to its emitting principally a single wavelength of light (see security lighting). In the field of Physical security, security lighting is often used as a preventative and corrective measure against intrusions or other criminal activity on a physical piece Due to the substantial size of the lamp, particularly in higher wattages such as 135 W and 180 W, control of light emissions from low pressure sodium luminaires is more difficult. For applications requiring more precise direction of light (such as narrow roadways) the native lamp efficacy advantage of this lamp type is decreased and may be entirely lost compared to high pressure sodium lamps. A sodium vapor lamp is a Gas discharge lamp which uses Sodium in an excited state to produce Light Allegations that this also leads to higher amounts of light pollution from luminaires running these lamps arise principally because of older luminaires with poor shielding, still widely in use in the UK and in some other locations. Modern low-pressure sodium fixtures with better optics and full shielding, and the decreased sky glow impacts of yellow light (see sky glow discussion) preserve the luminous efficacy advantage of low-pressure sodium and result in most cases is less energy consumption and less visible light pollution. Skyglow (or sky glow) is a kind of Light pollution, visible by the "glowing" effect seen in the skies over many cities and towns as a dome of light Unfortunately, due to continued lack of accurate information (see for example section 4. 10 What Types of Lamps Are Used in Outdoor Lighting? in the IDA Outdoor Lighting Code Handbook) many lighting professionals continue to disparage low-pressure sodium, contributing to its decreased acceptance and specification in lighting standards and therefore its use.

Because of the scatter of light by the atmosphere, different sources produce dramatically different amounts of skyglow from the same amount of light sent into the atmosphere. Diffuse sky radiation is Solar radiation reaching the Earth 's surface after having been scattered from the direct solar beam by Molecules For a discussion of these effects see the section on sky glow. Skyglow (or sky glow) is a kind of Light pollution, visible by the "glowing" effect seen in the skies over many cities and towns as a dome of light

Re-designing lighting plans

In some cases, evaluation of existing plans has determined that more efficient lighting plans are possible. For instance, light pollution can be reduced by turning off unneeded outdoor lights, and only lighting stadiums when there are people inside. Timers are especially valuable for this purpose.

One example of a lighting plan assessment can be seen in a report originally commissioned by the Office of the Deputy Prime Minister in the United Kingdom, and now available through the Department for Communities and Local Government. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located The Department for Communities and Local Government (branded as Communities and Local Government) is the United Kingdom government department for communities ^[45] The report details a plan to be implemented throughout the UK, for designing lighting schemes in the countryside, with a particular focus on preserving the environment.

In another example, the city of Calgary has recently replaced most residential street lights with models that are comparably energy efficient. Calgary (ˈkælgəriː is the largest city in the Province of Alberta, Canada ^[46] The motivation is primarily operation cost and environmental conservation. The costs of installation are expected to be regained through energy savings within six to seven years.

The Swiss agency for energy efficiency (SAFE) uses a concept which promises to be of great use in the diagnosis and design of road lighting, i. e. "consommation électrique spécifique (CES)", which can be translated into English as "specific electric power consumption (SEC)". [3] Thus, based on observed lighting levels in a wide range of Swiss towns, SAFE has defined target values for electric power consumption per metre for roads of various categories. Thus, SAFE currently recommends an SEC of 2 to 3 watts per meter for roads of less than 10 metre width (4 to 6 watts per metre for wider roads). Such a measure provides an easily applicable environmental protection constraint on conventional "norms", which usually are based on the recommendations of lighting manufacturing interests, who may not take into account environmental criteria. In view of ongoing progress in lighting technology, target SEC values will need to be periodically revised downwards.

See also

• Bortle Dark-Sky Scale
• Dark Sky preserve
• Earth Hour
• History of street lighting in the United States
• Lighting
• List of environmental health hazards
• National Dark Sky Week
• Over-illumination
• Scotobiology

References

External links

Related Organizations

• International Dark-Sky Association
  • Links and Web Resources
  • Austria: Verein Kuffner Sternwarte (How many stars?)
• Campaign for Dark Skies (UK)
• New England Light Pollution Advisory Group
• SELENE (New York)
• Citizens for Responsible Lighting (based around a distributed discussion group)
• Virginia Outdoor Lighting Taskforce
• Italian site of IDA-UAI-CieloBuio
• Spanish Cel Fosc
• Fatal Light Awareness Program (FLAP) (Toronto)
• Starlight: a common heritage.
• The Campaign for Dark Skies (CfDS) is part of the British Astronomical Association, and campaigns for reduced light pollution in the United Kingdom. The Campaign for Dark Skies (CfDS is the United Kingdom 's main anti- light-pollution campaign group The British Astronomical Association, BAA is the senior national association of Amateur astronomers in the UK. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located
• Sydney Outdoor Lighting Improvement Society

Research about light pollution

• The Challenge article "Is Light Pollution Killing Our Birds"
• The Discover article relating light pollution to insects, birds, and breast cancer (requires paid registration)
• Ecology of the night symposium (2003 conference)
• "Ecological Consequences of Artificial Night Lighting" (2002 conference, by the Urban Wildlands Group)
• Light pollution and the protection of the night environment, UNESCO, IDA Regional Meeting, 360 pages,(2002) English — Italian. Proceedings are available as a downloadable PDF.
• Sherbrooke College Light pollution research activities
• Adelaide's Light Pollution Examples of the good, bad and ugly lighting

Collections of links related to light pollution

• Open Directory Project: Light Pollution
• The Dark Side: an article in The New Yorker magazine about light pollution
• Astronomical Society of South Australia article on Light Pollution
• There is a petition available in Germany against light pollution until 27. December 2007
• ALI - the Alliance for Lighting Information - website contains information about light, lighting and related topics.
• Turn Out the Lights!