The problem of light pollution was first raised in the 1930s. It was first put forward by the international astronomical community, and it is believed that light pollution is the negative influence of the bright sky of urban outdoor lighting on astronomical observation. Later, Britain and the United States and other countries called it "interference light", while Japan called it "light damage".
At present, there is no clear definition of light pollution at home and abroad It is generally believed that light pollution refers to all kinds of light that affects the natural environment, adversely affects human normal life, work, rest and entertainment, damages people's ability to observe objects, causes human discomfort and harms human health. Optical radiation with wavelength from 10 nm to 1 mm, namely ultraviolet radiation, visible light and infrared radiation, may become the source of light pollution under different conditions.
Light pollution in a broad sense includes some things that may have adverse effects on people's visual environment and physical health, including the reflection of books, papers, wall coatings and even the "light" of roadside color advertisements, and the range of light contained in visible light pollution. In daily life, the common types of light pollution are mostly dizziness of pedestrians and drivers caused by the reflection of mirror buildings, and discomfort caused by unreasonable lighting at night.
Classification of light pollution
According to different classification principles, light pollution can be divided into different types.
Light pollution is generally divided into three categories in the world, namely white light pollution, artificial sunlight pollution and colored light pollution.
1. White light pollution
When the sun shines strongly, the glass curtain wall, glazed tile wall, polished marble and various paints of buildings in the city reflect light, which is bright and dazzling. Experts have found that people who work and live in an environment polluted by white light for a long time will suffer different degrees of damage to their retina and iris, and their vision will drop sharply. The incidence of cataract is as high as 45%. It can also make people dizzy and upset, and even cause insomnia, loss of appetite, depression, physical weakness and other similar symptoms of neurasthenia.
In summer, the strong reflected light from the glass curtain wall enters the nearby residential buildings, which raises the indoor temperature and affects normal life. Some glass curtain walls are semi-circular, and the convergence of reflected light is easy to cause fire. Drivers driving in the hot sun will suddenly be attacked by the reflected light from the glass curtain wall, and their eyes will be strongly stimulated, which is prone to car accidents.
According to the research of optical experts, the reflected light of mirror architectural glass is stronger than sunlight, and its reflectivity is as high as 82% ~ 90%, which reflects almost all the light, far exceeding the range that human body can bear. People who work and live in the environment polluted by white light for a long time are prone to vision loss, dizziness, insomnia, palpitation, loss of appetite and depression, which will change people's normal physiology and psychology and induce some diseases for a long time. Experts have found that people who work and live in an environment polluted by white light for a long time will suffer different degrees of damage to their retina and iris, and their vision will drop sharply. The incidence of cataract is as high as 45%. In summer, the strong reflected light from the glass curtain wall enters the nearby residential buildings, which destroys the original good indoor atmosphere and increases the average room temperature by 4℃ ~ 6℃. Affect normal life.
* Glare pollution
The headlights used for lighting when the car is driving at night and unreasonable lighting arrangement in the factory will cause glare. In some workplaces, such as railway stations, airports, and the central control room of automation enterprises, too many and too complicated signal lamp systems will also reduce the eyesight of workers, thus affecting work efficiency. Without proper protective measures, the strong light generated by the welding torch will also hurt people's eyes. Workers who work in strong light for a long time (such as smelters, melting chemicals, glass blowers, etc.). ) will also encounter strong light.
2. Artificial sunlight
After nightfall, advertising lights and neon lights in shopping malls and hotels are dazzling. Some intense light beams even go straight into the sky, making night like day, which is called artificial day. In such a "city that never sleeps", it is difficult to fall asleep at night, which disturbs the normal biological clock of the human body and leads to low work efficiency during the day. Artificial sunlight can also harm birds and insects, and strong light may destroy the normal reproduction process of insects at night.
At present, the excessive use of lights in big cities makes the sky too bright to see the stars, which affects astronomical observation and aviation, and many observatories are forced to stop working. According to astronomical statistics, when the sky is not polluted by light at night, about 7000 stars can be seen, while in big cities where street lights, background lights and landscape lights are scattered randomly, only about 20 to 30 stars can be seen.
3. Color light pollution
Black lights, rotating lights, fluorescent lights and flashing light sources installed in dance halls and nightclubs constitute color light pollution. According to the measurement, the intensity of ultraviolet rays produced by black light is much higher than that in sunlight, and the harmful effects on human body last for a long time. If people receive this radiation for a long time, they will cause nosebleeds, tooth loss, cataracts, even leukemia and other cancers. The dazzling color light source is not only bad for the eyes, but also interferes with the central nervous system of the brain, making people dizzy, causing nausea, vomiting, insomnia and other symptoms. The latest research by scientists shows that colored light pollution not only damages people's physiological functions, but also affects people's psychology. The measurement of "Chromaticity Effect of Spectral Light" shows that if the psychological effect of white light is 100, blue light is 152, purple light is 155, red light is 158, and black light is the highest, which is 187. If people are exposed to colored lights for a long time, their psychological accumulation effect will also cause burnout, dizziness, loss of libido, impotence, irregular menstruation, neurasthenia and other physical and mental diseases to varying degrees.
In addition, some scholars divide light pollution into outdoor visual environmental pollution, indoor visual environmental pollution and local visual environmental pollution according to the scope of light pollution. Among them, outdoor visual environmental pollution includes building exterior walls and outdoor lighting. Indoor visual environment pollution includes indoor decoration, indoor bad light and color environment. Local environmental pollution includes books, paper and some industrial products.
:: Laser pollution
Laser pollution is also a special form of light pollution. Because laser has the characteristics of good directivity, concentrated energy and pure color, and the light intensity when it reaches the fundus can be increased by millions to tens of thousands of times after passing through the lens of human eyes, laser does great harm to human eyes. Part of laser spectrum belongs to ultraviolet and infrared range, which will damage conjunctiva, iris and lens. High-power laser will damage deep tissues and nervous system of human body. In recent years, laser has been widely used in medicine, biology, environmental monitoring, physics, chemistry, astronomy and industry, and laser pollution has attracted more and more attention.
* Infrared pollution
In recent years, infrared rays have been widely used in military, artificial satellites, industry, health and scientific research, so infrared pollution problems have also arisen. Infrared ray is a kind of thermal radiation, which will cause high temperature damage to human body. Strong infrared rays can cause skin damage, similar to scalding, burning pain first, then burning. In several different situations, infrared rays can hurt the eyes. The infrared ray with the wavelength of 7500 ~ 13000 A has a high transmittance to the cornea, which can cause damage to the fundus retina. In particular, infrared rays around 1 1000 angstrom can make anterior media (cornea, lens, etc. ) the eyes are not damaged and directly cause fundus retinal burns. Almost all infrared rays with the wavelength above 19000 A are absorbed by the cornea, which will cause corneal burns (opacity and white spots). Most of the energy of infrared ray with wavelength greater than 14000 angstrom is absorbed by cornea and intraocular fluid, but it cannot penetrate iris. Only infrared rays below 13000 angstrom can penetrate the iris, causing iris damage. Long-term exposure of human eyes to infrared rays may cause cataracts.
* UV pollution
Ultraviolet rays were originally used for disinfection and some technological processes. In recent years, its application has been expanding, such as satellite detection of the ground. The effect of ultraviolet light varies with wavelength. The vacuum ultraviolet part with the wavelength of 1000 ~ 1900 angstrom can be absorbed by air and water. Most of the far ultraviolet with the wavelength of 1900 ~ 3000 angstrom can be strongly absorbed by biomolecules; The near ultraviolet part with the wavelength of 3000 ~ 3300 angstrom can be absorbed by some biomolecules.
Ultraviolet rays mainly harm cornea and skin. The ultraviolet rays that cause corneal damage are mainly 2500 ~ 3050 angstroms, and the wavelength of 2880 angstroms is the strongest. Repeated exposure of cornea to ultraviolet rays does not increase its tolerance to ultraviolet rays. The harmful effect of ultraviolet rays on cornea is a very painful corneal leukoplakia injury, which is called photophobia. In addition to severe pain, it can also lead to tears, eyelid spasm, conjunctival congestion and ciliary muscle twitching. The harmful effects of ultraviolet rays on the skin mainly cause erythema and blisters, and in severe cases, the epidermis will be necrotic and desquamate. The skin of human chest, abdomen and back is most sensitive to ultraviolet rays, followed by forehead, shoulders and buttocks, and then the soles of feet and the back of hands. Ultraviolet rays with different wavelengths have different effects on the skin, and ultraviolet rays with wavelengths of 2800 ~ 3200 Angstroms and 2500 ~ 2600 Angstroms have the strongest effects on the skin.
Light pollution in a broad sense also includes:
visual pollution
Refers to the chaotic visual environment in the urban environment. For example, there are messy wires, telephone lines, messy garbage, messy booths and colorful advertising posters on both sides of the city streets.
There are many other ways to classify light pollution. For example, in Wikipedia, we see that light pollution can be divided into the following categories:
Mild pressure (mild invasion)
This kind of "pollution" mainly means that the light source exceeds the standard and affects the daily rest of others. For example, the lights at night make it difficult to sleep. At present, all countries have relevant laws to protect their people from infringement.
Overlighting
Overlighting is mainly the meaningless use of wasting energy. The energy wasted by "over-lighting" in the United States every day is equivalent to 2 million barrels of oil!
Clutter (mixed light)
Different kinds of light sources mixed together will seriously affect passive recipients. And it may lead to a car accident. What is even more frightening is that for pilots flying at night, it takes energy to find and identify aviation signal lights in these various lights.
Glare (glare)
Light in the dark. It will make pedestrians or drivers temporarily "blind", which will lead to traffic accidents. And in the case of improper protection, this strong light will also hurt people's vision.
Sky glow (artificial sunlight phenomenon)
Artificial sunlight will seriously affect the work of astronomers and destroy the ecological environment.
In a word, light pollution will lead to energy waste and damage people's physical and mental health. In addition, excessive light pollution will seriously damage the ecological environment and have a negative impact on traffic safety and space research. Before the government effectively adjusts the light source, it must pay attention to stay away from similar pollution sources.
Ma Jian, a professor at Tianjin University in China, divided light pollution into "daytime light pollution" and "night light pollution" according to its occurrence and influence time. The white light pollution mentioned above belongs to daytime light pollution, while artificial daytime and colored light pollution belong to luminous pollution. I won't elaborate on this classification here.