Importance Of Light In Hygiene
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This document discusses the hygienic bases of illumination. It covers the physical properties of visible light, as well as the biological and physiological effects of visible light, ultraviolet light, and infrared light. It also discusses factors that affect indoor illumination levels, hygienic norms and standards for indoor illumination, and potential health effects of insufficient lighting. Recommendations are provided for natural and electric lighting of rooms to ensure proper illumination.
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Importance Of Light In Hygiene
- 1. Hygienic bases of illumination
- 2. Learning outcomes After lecture you should know: • Physical bases of visible light • Biological, physiological and hygienic role of visible, ultraviolet and infrared waves • Factors effecting the level of indoor illumination • Hygienic norms of indoor illumination • Health effects of insufficiency of illumination • The role and norms of room Insolation • Hygienic assessment of natural and electric room illumination
- 4. Physical bases of visible light • A radiation energy causing a sense of light • 360-760 nm • Our eyes are most sensitive to the middle part of the optical spectrum and have the maximal sensitivity to wave length 555 nm (yellow-green part) • The capacity of this radiation is called a light stream (F, lumen) • A light exposure (e) is a ration of a stream light to a surface square: e= F/S (lux) • A coefficient of natural light exposure is a ratio of indoor light exposure level to outside light exposure measured at the same height level and time (Ce, %)
- 5. Biological, physiological and hygienic role of visible light • More than 80% of information from the outer world • Effects on all body organs and systems very favourably • Stimulates metabolism, improves a general functional status of a body, emotional mood, and increases workability • Has a thermal effect • Leader of the biological rhythm of life • Improper and insufficient light affects negatively on functions of the vision organs, increases fatigability of vision organs and the CNS in general. • Insufficient illumination decreases work efficiency (productivity) of labour, promotes growing occupational traumatism
- 6. Ultraviolet waves 100-400 nm UVL of 100-290 nm do not reach the Earth surface The most active part of light in connection to the biological activity of UVL “Nothing to do for a doctor where sun looks” The UVL affects on our skin not only by local changes of cellular and tissue proteins but on all our body through the extra and intra receptors of skin Biological properties of the UVL depend on the wave’s length.
- 7. A (400-320nm) • fluorescent part (luminofores) • sunburn light (tyrosine/melanin) B (320-280 nm) • the most valuable • very stimulative action on a body • Erythema after 6-8 h promotion of the growth & regeneration of cells, body resistance against infectious agents, toxicants, carcinogens, etc • Stimulates amino acids and purine & pyrimidine parts of proteins choline, acetylcholine, histamine, etc • Part D (315-265 nm) has antirachitic effect (Vit D) C (280-200 nm) • Also affects in vitamin D synthesis • Main part with bactericidal effect • The maximum of this bactericidal effect is due to 254 nm UVL
- 10. The UVL deficiency & surplus • The UVL deficiency Rachiotis, decreasing general resistance, upset of metabolic processes • The UVL surplus provocation of chronic diseases (tuberculosis, ulcer, rheumatism, etc) • The UVL surplus mutagenic and carcinogenic effects.
- 11. Infrared Waves (760-25 000 nm) Short (Far) IR waves 760-1400 nm • the deeper they penetrate in tissues, but feelings are marked less Long IR waves 1400-25000 nm • absorbed by superficial layers of skin with thermoreceptors --> we feel burn
- 12. Illumination in a room The natural illumination of premises is created by light passing the windows and lanterns and light reflecting ceiling, walls, floor etc. General light environment is formed as a result of interaction of direct and reflected light in a premise. • Height of the sun stand • Character of cloudiness • Transparency of the atmosphere • Condition of a terrestrial cover • Smoke and air pollution • Season of a year • Near buildings or trees and their outside decoration • Heights of a floor, height of the windows, their shape, types and cleanness of window’s glasses • Interior decoration and furniture and the height of ceiling
- 13. Standardization of Illumination • Lateral (through windows) • Top (through lanterns) and • Combined (through windows and lanterns) • coefficient of natural light exposure (еmin %) at system of lateral illumination, at systems of the top and combined illumination (еave) • In living rooms, hospital wards emin should be not less than 0.5%. in classes it should be > 1%. It means that the indoor light exposure should be not less than 1 % of outside level
- 14. Vision impairment due to irrational illumination Overfatigue of sight Due to insufficient light exposure, intense visual work on close distance, often re-adaptation, and presence of stroboscopic effect. Pain in area of forehead, eye apples, deterioration of visibility, hyperemia of eye apples, swollen eyelids, epiphora, and sometimes conjunctivitis Short-sightedness (myopia) At long work on close distance, it is necessary to consider weakness of accommodation
- 16. Basic hygienic requirements to electric illumination • Favorable spectrum of radiation and continuous light flow of a light source. • Sufficient light exposure of working surfaces and premises. • Uniform distribution of brightness on working surfaces and in working premises. • Absence of sparkles in a field of sight of workers.
- 17. Hygienic assessment of illumination • emin, % - 1-1.5% • Light coefficient, CoL - 1:4, 1:6 • Angle of incidence, o BAC - 27o • Opening angle, o EAC - 5o
- 18. Reference • Eric E. Richman. Requirements for Lighting Levels. https://www.wbdg.org/pdfs/usace_lightinglevels.pdf • Lighting. 1915.82. General Working Conditions. Occup. Safety and Health Standards for Shipyard Employment. https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_tab le=STANDARDS&p_id=190
Editor's Notes
- A radiation energy causing a sense of light is called an optical radiation. The spectrum of optical part of sun light is from 360 nm to 760 nm. The capacity of this radiation is called a light stream (F, lumen). Our eyes are most sensitive to the middle part of the optical spectrum and have the maximal sensitivity to wave length 555 nm (yellow-green part). A light exposure (e) is a ration of a stream light to a surface square: e= F/S (lux). A coefficient of natural light exposure is a ratio of indoor light exposure level to outside light exposure measured at the same height level and time (Ce, %).
- In spite of that optical radiation has a very narrow diapason of electromagnetic radiation (380-760 nm) it plays a very big biological, physiological and hygienic role. The main property of the light is an ability to cause sense of light. Vavilov Sergei sad: “Light is a necessary condition for work of our eyes, the most delicate, universal and mighty feeling organ”. Light gives more than 80% of information from the outer world. It influences through the eyes and central nervous system on all organs and systems of a body very favourably, it stimulates metabolism, improves a general functional status of a body, emotional mood, and increases workability. Imagine, you are awakened and first, you see, is a bright sun light in your room. Right this moment you feel good mood, you are glad you are living in this world. This world seems to you the most beautiful world. The light has a thermal effect; the half of the general thermal energy of the sun light is a share of the optical part. The sun light is a leader of the biological rhythm of life on our planet, and first of all, for human. From the ancient time, a man used to wake up with sunrise and go to sleep with sunset. All physiological functions go in accordance with a certain day rhythm. Improper and insufficient illumination affects negatively on functions of the vision organs, increases fatigability of vision organs and the central nervous system in general. At a working place insufficient illumination decreases work efficiency (productivity) of labour, promotes growing occupational traumatism. It is proved that during work for 3 hours by 30-50 lux of illumination the stability of clear vision decreases by 37%, by illumination 200 lux, it decreases only by 10%. Rational and sufficient illumination is especially necessary for modern computerized occupational places, when the role of an operator’s work and the status of sense organs and nervous centres become very important; when exactness and rapidity of reactions play decisive role. The large hygienic and psychological importance of the correctly designed natural illumination of premises consists first of all in creation of general light environment in a premise, favorable for visual work.
- The sun light sanitizes the environment. They say: “Nothing to do for a doctor where sun looks”. Where illumination is better there is cleaner, drier. This is because of ultraviolet part of the sunlight. The ultraviolet light (UVL) is the most active part of light in connection to biological activity. The UVL is the light with wave’s length 100-400 nm. But the UVL with 100-290 nm do not reach the Earth surface. The UVL affects on our skin not only by local changes of cellular and tissue proteins but on all our body through the extra and intra receptors of skin.
- Biological properties of the UVL depend on the wave’s length. The UVL spectrum is divided into 3 parts: A (400-320nm), B (320-280 nm), and C (280-200 nm). The A part is the fluorescent part. It causes lightening of several substances (luminofores). This part also is called sunburn light because due to this UVL part pigments are formed in our skin. In skin cells melanin is formed from tyrosine/melanin is protective means from the UVL surplus. The B part is the most valuable UVL. It has very stimulative action on our body. After 6-8 hours of radiation we have erythema. The mechanism of stimulative effect of the B UVL consists on its ability to stimulate (provoke) amino acid parts (tyrosine, triptophane, phenylalanine, etc) and purin and pirimidin substances of proteins (thymine, cytosine, etc). This stimulation continues in dissociation of proteins (photolysis) and formation of physiologically active substances (choline, acetylcholine, histamine etc). This erythematic stimulation of the UVL leads to promotion of the growth and regeneration of tissues, body resistance against infectious agents, toxicants, carcinogens, etc. The B UVL with 315-265 nm named as part D has antirachitic effect. While this light acts, in the skin cells cholecalciferoli (vitamin D3) is formed from 7,8-dehydrocholesteroli in skin fat. The C part of the UVL also affects in vitamin D forming, but the main its effect is bactericidal effect. The maximum of this bactericidal effect is due to 254 nm UVL wave.
- Thus, the UVL insufficiency can lead to pathological conditions in our body. First of all it is Rachiotis, decreasing general resistance, upset of metabolic processes. The UVL surplus can bring to provocation of chronic diseases (tuberculosis, ulcer, rheumatism, etc). The UVL surplus can cause mutagenic and carcinogenic effects. With the preventive purposes, the UVL is recommended for people working in places without sunlight or people living in the North.
- The infrared light is waves with length 760-25 000 nm. They are divided into 2 parts: short IRL waves (760-1400nm) and long IRL waves (1400-25000 nm). The shorter the length of waves the deeper they penetrate in tissues, but feelings are marked less. Vice versa, the long IRL wave are absorbed by superficial layers of skin, where we have thermoreceptors. That is way we feel burn. The IRL affects in organic changes in eyes when the light acts for a long time. In some cases they cause cataract.
- The natural illumination of premises is created by light passing the windows and lanterns and light reflecting ceiling, walls, floor etc. General light environment is formed as a result of interaction of direct and reflected light in a premise. The size of light exposure on an open place of the sky depends on height of the sun stand, character f cloudiness, transparency of an atmosphere and condition of a terrestrial cover. The air transparency renders an essential influence on size of outside diffuse light exposure. Smoke and pollution of air in the metropolises and large industrial areas essentially reduce outside light exposure. The influence of conditions of a terrestrial cover on outside light exposure reaches the greatest meaning in winter months, when the ground is covered with snow. The near buildings or trees and their outside decoration also influences on the illumination level in a premises. The heights of a floor, height of the windows, their shape, types and cleanness of window’s glasses have also impacts on illumination. In the premises, the interior decoration and furniture and the height of ceiling impact on illumination.
- There are three systems of natural illumination: lateral (through windows), top (through lanterns) and combined (through windows and lanterns). According to the mentioned systems the sufficiency of light exposure of premises is regulated: а) by the minimal meaning of coefficient of natural light exposure (еmin %) at system of lateral illumination, б) Average meaning of coefficient of natural light exposure at systems of the top and combined illumination (еave). In living rooms, the simple hospital wards emin should be not less than 0.5%. in classes it should be > 1%. It means that the indoor light exposure should be not less than 1 % of outside level. The norms of natural illumination are established with the account that clearing of glasses in premises with insignificant dust, smoke and soot is made not less often than 2 times a year, and in premises with significant dust, smoke and soot - not less often than 4 times in a year. Therefore, clearing of glasses of light apertures should be made in specified terms. It is necessary to finish ceilings, wall, partitions, floors, design, and also the process equipment mainly in the light tone ensuring increase of light exposure of workplaces at the expense of reflected light from internal surfaces of a premise.
- Overfatigue of sight. The reason of this can be insufficient light exposure, intense visual work on close distance, often readaptation, and presence of stroboscopic effect. It is expressed in the acute phenomena by the end of a working day. People complain on a pain in area of forehead, eye apples, deterioration of visibility, etc. At medical survey it is possible to note the phenomena of hyperemia of eye apples, swollen eyelids, epiphora, and sometimes conjunctivitis. Short-sightedness (myopia) meets among the same trades and has the same reasons. As the basic internal reason, at long work on close distance, it is necessary to consider weakness of accommodation. Because of that lengthening of frontal axis of eyes takes place. It is not excluded, that the main importance in progressing short-sightedness in consists in weakness of sclera.
- Area latitude, orientation of the building to the cardinal, the presence of shading opposing buildings, the distance between them, the height and color of the walls, as well as the proximity of green spaces – all it influences on the level of natural lighting. The square of windows, their shape and location are also of great importance. All these factors determine the duration and intensity of room lighting by direct sunlight, ie, Insolation of rooms. Hygienic classification takes into account the duration of insolation of premises. Insolation have general therapeutic, antibacterial and psychophysiological effects of direct sunlight, as well as the optimal combination of all the factors with the minimum values of each of them. The scattered and reflected light coming into the room, free of many parts of the solar spectrum of both visible and ultraviolet range, absorbed various objects (the surface of the earth, the trees, the walls of buildings, clouds, etc.) cannot be considered physiologically and sanitary as a full-fledged. Insolation regime must take into account when targeting buildings for various applications. In the northern latitudes, orientation of windows on the south side provides higher light levels and prolonged sun exposure compared to the north. In the middle and southern latitudes, for residential, educational buildings and the main production areas of pharmacies (aseptic unit assistant, room specialist analyst, filling, office manager) the best orientation of providing adequate illumination and insolation premises without overheating, it is the southern and south-east, eastern side orientation. It contributes to a certain extent, reorganization of air that occurs due to penetration and exposure to sunlight, which is enough germicidal energy to regenerate the internal environment of premises under normal conditions. Premises that do not require high insolation and the action of direct sunlight should orient their windows to the north, northwest, northeast. This auxiliary facilities pharmacies (physical facilities, washing, distillate translation-sterilization), premises of hospitals (operating theaters, intensive care, bandaging, treatment rooms, kitchens), the offices of drawing, painting, computer science and fitness facilities for children and educational institutions, residential buildings cuisine. This orientation provides a uniform natural lighting and eliminates overheating. Western orientation causes overheating of buildings in summer and winter, the lack of insolation. Illumination of premises depends on the degree of reflection of light, which is determined by the color of the ceiling, walls, floors and equipment in the room. Dark colors absorb more light and light color increases the brightness by reflected light. White and light colors provide the reflection of light rays by 70-90%, light yellow color - 60% light green - by 46%, the color of natural wood - 40%, Blue - 25%, dark yellow - 20%, light brown - 15% dark green - 10%, blue, and violet - 6-10%. For finishing the ceiling in premises, the white color is recommended, for the walls - bright colors of yellow, beige, pink, green, blue, for furniture - the color of natural wood for doors and for window frames - white. Recommendations for the color design of premises should take into account the effect of visible light on the human body. Red and yellow colors have a bracing effect, blue-violet - soothing. In the northern areas for painting the walls of the premises, shades of yellow and orange are recommended. They are simulating sunlight. In southern regions it is favorable to use shades of teal, mitigating shine sunlight indoors.
- The spectral characteristics of lighting installations should be whenever possible approached to a spectrum of natural light, for what, as a rule, discharge (luminescent) lamps, and also incandescent lamps are used. From the hygienic point of view, most important characteristic of light sources is the spectrum of radiation. Incandescent lamps. They have a continuous spectrum of radiation, however in comparison with natural light in this spectrum a plenty of orange-red and insufficient of blue and violet waves. Influence of such spectrum on the basic visual functions of eyes, visual serviceability less favorable, than at natural light. The incandescent lamps do not provide correct colourtransfer. Discharge lamps. In discharge lamps The colourtransfer of this lamp is better than the incandescent lamp. They are very economical.