Health aspects of lighting used in households
Zdrowotne aspekty oświetlenia stosowanego w mieszkaniach
Zakład Szkodliwości Fizycznych, Fizjologii Pracy i Ergonomii, Instytut Medycyny Pracy i Zdrowia Środowiskowego w Sosnowcu
Światło i jego praktyczne zastosowanie w formie oświetlenia odgrywa istotną rolę w życiu człowieka, ponieważ generuje wrażenia wzrokowe, kształtuje doznania psychiczne i rytm funkcji życiowych. Sposób, w jaki światło determinuje możliwości wizualne i reakcje fizjologiczne, zależy od właściwości oddziałujących bodźców świetlnych. W artykule podano drogi oddziaływania światła na człowieka, omówiono ilościowe i jakościowe parametry oświetleniowe kształtujące warunki widzenia i klimat świetlny we wnętrzach oraz podkreślono możliwe negatywne skutki zdrowotne niedoboru lub nadmiaru bodźców świetlnych w otoczeniu. Przybliżono także, z uwzględnieniem aspektu ekologicznego, zalety i wady nowoczesnych źródeł oświetleniowych stosowanych do oświetlenia mieszkań. Ponieważ światło wpływa na sprawność widzenia, samopoczucie, a nawet zdrowie człowieka, dobre oświetlenie można uznać za podstawową potrzebę w naszym życiu codziennym. Redukcję szkód wywołanych nieprawidłowymi warunkami oświetleniowymi można osiągnąć, stosując się do zaleceń podanych w artykule oraz korzystając ze wskazówek osób zajmujących się kreowaniem oświetlenia we wnętrzach.
Light and its practical application in the form of lighting plays an important role in human life, because it generates visual impressions, shapes mental experiences and the rhythm of vital functions. The way in which light determines visual capabilities and physiological reactions depends on the properties of the interacting light stimuli. The article presents the ways of its influence on human beings, quantitative and qualitative lighting parameters shaping the visual conditions and the light climate in the interiors were discussed, and possible negative health effects of deficiency or excess light stimuli in the environment were underlined. The advantages and disadvantages of modern lighting sources used for housing lighting have also been approached, taking into account the ecological aspect. Because light affects the efficiency of vision, well-being, and even human health, good lighting can be considered as a basic need in our everyday life. The reduction of damages caused by incorrect lighting conditions can be achieved by following the recommendations given in this article and using the instructions given by the interior lighting creators.
Słowa kluczowe: światło, parametry oświetleniowe, proces widzenia, zegar biologiczny, świetlówki i lampy LED
Key words: light, lighting parameters, vision process, biological clock, fluorescent lamps and LED lamps
Light plays a key role in human life. Light stimuli, through the organ of sight, provide people with over 80% of information about the surrounding environment (1). In addition to generating visual impressions, the influence of light on the physiology of the human body is also important. The changes of light shape the rhythm of its vital functions and evoke specific mental experiences. In everyday life, one can observe that lighting too strong, especially an artificial one, causes irritation, while darkening of lighting, in certain situations, promotes relaxation. In addition, during spring and summer, we are generally full of energy, while during fall and winter our activity decreases. There may also be other effects of lighting impact on the well-being and even human health, which we are not always aware of, and which depend on the quantitative and qualitative properties of the interacting light stimuli. Therefore, it is very important to know how to apply the light properly in places where the contemporary man stays the longest, ie. in households, schools and at work.
Light is electromagnetic radiation with wavelengths in the 380-780 nm range. These waves have the ability to evoke visual impressions in the human eye, therefore the light is called visible radiation (2, 3).
The evolutionary conditions of life on Earth make the human body needs the entire spectrum of sunlight (4). Also, the human vision was adapted to receive the entire range of visible radiation intensity of the Sun reaching the Earth (5).
The ways of the interaction of light on the human body
The course of the human vision process is well recognized. The classic path of light stimulus causing visual impression is: the optic system of the eye, retina (where the light stimulus is transformed into a nerve stimulus), optic nerve, visual intersection, visual band, lateral geniculate body, visual radius and visual cortex of the occipital lobe (6), which follows the final visual perception.
The share of visible radiation in the regulation of physiological processes in the human body is slightly less known. The human body is equipped with an endocrine (hormonal) system that activates various human body systems, adapting them to changing environmental conditions (6). Endocrine interferences are made by hormones that are transmitted through the blood to the target cells, where they regulate many vital processes. As established, the endocrine gland characterized by a significant sensitivity to light stimuli is pineal gland. During the aforementioned visual path, a part of the visual-ganglion neurons leaves the visual junction, running directly to the suprachiasmatic nucleus of the hypothalamus, and from there through the spinal cord and the upper cervical ganglion form connections with the pineal gland (fig. 1), which in turn secretes hormones – serotonin and melatonin (6, 7).
Fig. 1. The way light affects the pineal gland
In the absence of light stimuli, the secretion of melatonin increases, while light inhibits its secretion (secretion), triggering serotonin production.
Melatonin of pineal origin is released into the bloodstream and then reaches all organs. An adult emits 12.3-28.8 μg of melatonin daily, and the concentration of this hormone in the blood varies from 0-20 pg/ml during the day to 80-150 pg/ml during the night (7, 8). The balance between the melatonin and serotonin secretion cycles is essential for maintaining the so-called clock/biological rhythm (24-hour of activity and rest cycle). This innate ability to measure time helps the body to adapt its activities to the time when their performance is most important. For example: when the evening falls, the amount of melatonin increases. Melatonin, reaching the appropriate receptors, lowers body temperature, which makes falling asleep much easier (9).
The amount and quality of light needed for the effective functioning of the body
Proper lighting – using natural (solar) or artificial light – determines the efficiency and comfort of vision. Interior lighting technology is based on knowledge about human psychophysiology. Taking into account the properties of the human eye, it has been established that in order to obtain a good quality of vision one should assure (10):
– sufficient levels of light intensity – to allow/facilitate perception,
– uniformity of light intensity, uniform distribution of luminance in the vision field and limiting the phenomenon of glare – not to overload the eyes adaptive mechanisms and provide visual comfort,
– the appropriate colour of light and the appropriate light-rendering ability of used lighting sources – to provide the appropriate light climate, generate psychological feelings, facilitate the perception of colour sensations.
When designing the lighting of a given room, first it is determined what function it performs, how precise visual works are carried out in it, and then based on the lighting standards, the values of the above lighting parameters are selected.
The place where people spend most of their time after work or study are households. Inhabitants lighting issues are usually solved intuitively, because on the issues of house lighting they do not pay too much attention, or do not know how they can provide optimal lighting in their households. However, familiarity with the basic principles of proper lighting can help taking right decisions about lighting solutions.
The basic requirement is to provide adequate levels of lighting intensity on the main areas of work and walking routes. Taking into account the minimum values of illuminance for various activities and rooms given in Polish Standards PN-84/E-02033 or PN-EN 12464-1 (11, 12), it is possible to determine lighting levels suitable for rooms/home situations (tab. 1).
Tab. 1. Recommended values for illuminance levels in households
|1||corridors, stairs||50-100 lx|
|2||table in the dining room||200 lx|
|3||kitchen countertop/preparing a meal||300 lx|
|4||learning desk||500 lx|
|5||sewing, ansambling small items||750 lx|
Light in the house should not only facilitate the performance of life activities, but also enable relaxation, affect the well-being of the residents. Not without significance in creating the light climate is the colour of the light used, described by the so-called colour temperature Tb expressed in Kelvin [K] (the value of the colour temperature is given on the holder or packaging of the light source). Light warm white (Tb < 3500 K) has a relaxing and calming effect on humans, while white light (Tb = 3500-5500 K), and even more cool white (Tb > 5500 K) increases concentration and stimulates action. Therefore, light sources with a warm white colour should be used in bedrooms, in places of relaxation, while white/cool white light sources – in places where we perform precise work (writing, sewing, preparing meals).
The visual property is also influenced by the property of light called the colour rendering ability. It is called the so-called colour rendering index Ra. The higher Ra is (Ra takes values from 0 to 100), the better rendered are colours of observed objects, and the objects themselves (even the tone of human skin) look more natural. It is assumed that the best colour rendering index has got natural sunlight. Lighting source, in the light of which the observed colours are not distorted (they look very similar to natural light) has good colour rendering ability and can be used in places where colour discrimination is important (e.g. watching photos, make-up making).
Lighting in the house should be useful, but also adapted to the current needs and individual preferences of its residents. Therefore, it is advisable to illuminate a given residential interior with at least several lighting sources, appropriately arranged and used depending on the situation. In general, it should consist of diffuse general (base) lighting, local (task) lighting and spotlight (decorative) accents. By properly arranging the light fittings of the three types of lighting, choosing the amount, colours and Ra of the applied light, it is possible to create the lighting conditions desired by the residents.
It is a mistake to underestimate the role of proper lighting. An undesirable condition is the so-called underexposure of the interior (13), which may occur due to lack of sunlight resulting from the time of day and season, weather, too small window openings, and in rooms in which artificial light dominates – as a result of poor positioning of lamps, mismatch of the level of illumination to the work performed or individual needs of the user, e.g. people with visual impairments or elderly people.
In many rooms, there are relative lighting conditions at which the user is able to do the work, but this is only possible due to the large adaptation possibilities of the eye and general body’s ability to compensate for poor environmental conditions. These adaptive and compensatory abilities are limited and the effects may be quickly manifested, such as: decreased visual performance, fatigue and eye discomfort, refractive errors, states of depression resulting from gloomy ambient.
Intended use of low levels of illumination in living rooms in rest situations is justified, but the issue of proper lighting of children’s and youth’s learning places can not be underestimated. Reading, writing, working on a computer monitor should be done in good lighting. It was found that it is not the workload itself, but reading from a distance too close (the child leans towards the book or the notebook at a low level of illumination) is of the greatest importance in the development of myopia in children (14). Work at the desk and artificial lighting should also be limited in time. According to Rose et al. (15), the factor preventing the development of myopia is frequent open-air activities. Among others a positive role is played by sunlight, which indirectly slows down the eyeball growth in children, contributing to myopia (16).
Sufficient lighting in households is also important for older residents. Properly illuminated places of visual work (kitchen countertop, reading areas, DIY, body care) and corridors and passages, help in safe movement, encourage to action. Due to anatomical and physiological changes in the eye organ, older people require higher levels of light intensity compared to young people. In comparison with the eye of a twenty-year-old person, only 1/3 of the light reaches the older person’s eye due to the smaller diameter of the pupil and clouding of the lens (17), which should be taken into account when choosing lighting in elderly people’s dwellings.
With regard to the aspect of visible radiation in the regulation of physiological processes in the human body, it should be remembered that the contemporary man spends most of his life in interiors lit with artificial light, differing in quantity and quality from the daylight. In rooms, the intensity of lighting is usually 100-750 lx, when outside 2000-5000 lx on a cloudy day, and on a sunny day even 100,000 lx (9). As a result of chronic, poor light stimulation, the biological rhythm may desynchronise. Most people do not mind, because light replaces other time regulators: fixed working hours, regular meal times. However, in susceptible people, among others older people, desynchronization occurs, resulting in: sleep disorders, appetite, lack of energy, mood crisis. Such desynchronization also often appears in vulnerable people in the autumn and winter season, when sunlight is less. The consequence of this is the so-called seasonal depression also called seasonal affective disorder (seasonal affective disorder – SAD) (18).
Another extreme situation related to the participation of light in human life is an excess of light stimuli in the environment. In the case of households it may occur as a result of excessive lighting of rooms, use of only general lighting without the use of local lighting, not turning off unnecessarily lamps. However, there are also certain habits of residents associated with the „excess” of light – i.e. sleeping with the lamps, TV or computer turned on. As many scientific reports have stated (19-21), the habit of sleeping with the light turned on is not beneficial for the body, especially the developing one. It plays important role for newborns. In order to prevent damage to developing eyesight and to prevent disturbances in the diurnal rhythm of babies, at neonatal care, by night, intensive lighting is reduced to just a few lux (19). According to Czepita (20), people who have slept in illuminated rooms up to two years are more likely to have refractive disorders. There are also reports on the correlation between the effects of light on a human being at night (so-called LAN – light at night) and the appearance of obesity, diabetes, depression (7, 21) and an increased risk of breast cancer and prostate cancer (22). This is related to the disturbances of the biological rhythm, caused, as mentioned before, by the inhibition of melatonin secretion, while the increased production of cortisol, testosterone, and estrogen, and the reduction of the immune system activity. The problem is that the light at night often does not come from our night lamps, but penetrates through the windows from the outside. The harassing light of, for example, advertising fluorescent laps, a residential street lamp disturbing the natural rest can cause negative emotional reactions (stress), and after some time – the health effects mentioned above.
Advantages and disadvantages of modern light sources
Until recently, the most commonly used sources of light in households were incandescent sources, but their time is already over. In the years 2009-2016, the process of withdrawal of light incandescent bulbs and replacing them with modern sources, which mainly include compact fluorescent lamps and LED lamps, was carried out. The advantages of incandescent sources were a continuous spectrum of radiation, similar to the solar spectrum, ease of use, low cost, high diversity of their power and supply voltages, friendly, warm colour of light. In turn, the disadvantages of light bulbs were energy consumption, low luminous efficiency – within 8-14 lm/W, high bulb temperature.
In compact fluorescent lamps, light is produced in the same way as in ordinary fluorescent lamps – the inside of a fluorescent tube is compacted with a phosphor layer and filled with a small amount of noble gas (under pressure of 400 Pa) and metallic mercury. As a result of the current flow between the electrodes mercury vapour is formed. The electrical stimulation of this vapour leads to the emission of ultraviolet radiation with wavelength 253.7 and 185 nm. A phosphor covering the inner surface of fluorescent tubes transforms ultraviolet radiation into visible light. By dividing the glass tube into several parts, their appropriate shape, and then connecting with the ignition-stabilization system, it was possible to achieve such dimensions of the fluorescent tube that it became a replacement for a standard light bulb. Table 2 compares the power of incandescent light bulbs and fluorescent tubes emitting the same luminous flux (parameter defining the amount of light emitted by the light source per unit of time).
Tab. 2. „Fluorescent” equivalents of incandescent bulbs, acc. (23)
|Lamp type||Luminous flux in [lm]|
|light bulb||25 W||40 W||60 W||75 W||100W||150 W|
|fluorescent bulb||5 W||7-9 W||11-13 W||14-15 W||18-23 W||30 W|
The advantages of compact fluorescent bulbs are: high luminous efficiency from 33 to even 104 lm/W, durability 6,000-20,000 h, high Ra index (from 80-90) and different colour temperatures. The disadvantages of fluorescent bulbs are: the need to use auxiliary devices (ballast, igniter), the influence of the number of switches on the durability of the fluorescent tube, difficult ignition at low temperatures and at reduced voltage, and the pulsation of the luminous flux. What distinguishes the compact fluorescent bulb from the incandescent bulb is the spectrum of radiation, which is called bandwidth spectrum (discontinuous).
When using compact fluorescent lamps to illuminate households, it should be remembered that a fluorescent lamp is classified as hazardous waste, and a broken or cracked fluorescent lamp is a particularly dangerous waste due to the mercury contained there. Mercury is a toxic heavy metal that when entering the human body can cause many dangerous diseases, ranging from headache and limbs pain, gastrointestinal mucous membrane inflammation to central nervous system and kidney damage.
According to public opinion polls (24), more than half of fluorescent bulb users throw them into the rubbish. Only every tenth Pole dispose the so-called energy-saving bulbs to the local waste disposal centre. European regulations on the obligation to supervise electro-waste are introduced into Polish law by the Act of 29 July 2005 on Waste Electrical and Electronic Equipment – WEEE (25). Pursuant to the Act, waste holders in the form of used light sources containing mercury, they should return this waste to their collection points. An important skill is also the handling of a broken fluorescent lamp at home, in a way that limits the possibility of poisoning with mercury vapour. If the fluorescent bulb breaks, open the window and ventilate the room for a minimum of 15 minutes to remove mercury vapours. The next step is to protect the broken elements of the fluorescent bulb. Put on rubber gloves and gently collect broken parts of the fluorescent bulb (do not use a vacuum cleaner for this purpose), and wipe the place from which the parts of the fluorescent bulb have been collected using a disposable, wet towel. Collected leftovers of fluorescent bulb, gloves and used towels should be placed in a sealed plastic bag and sealed with tape. Then wash your hands and transfer the protected material to the WEEE collection point.
The second group of modern lighting sources are LED sources (light emitting diode – LED), which use the phenomenon of current flow through semiconductors (so--called p-n connector) for the emission of light. LEDs were made in the 1960s, but initially they were red light emitting diodes. The next step in the development of LED technology was to produce LEDs emitting white light, in the so-called LEDs, equipped with shafts used in traditional incandescent lamps, the way to obtain white light is to create a blue light in the p-n connector, affecting the phosphor, which, mixing with the yellow light produced by the phosphor, results in white light (the so-called hybrid method). The light produced in this way has a high colour rendering index (Ra > 80), different colour temperatures (from 2700 to 6500 K), and luminous efficacy in the range of 50-140 lm/W. These high efficiencies allow to achieve 80% energy savings compared to incandescent bulbs and 30% compared to compact fluorescent lamps. Energy-saving LED sources, independent of the switching on and off frequency, durability (25,000-100,000 h), resistance to shock, no infra-red radiation and the insignificant share of ultraviolet radiation makes them increasingly used in households. To facilitate the selection of the „LED” replacement for light bulbs, some manufacturers give the approximate value of the power of a traditional light bulb emitting the same luminous flux as the considered LED source. This is presented in table 3.
Tab. 3. „LED” equivalents of incandescent bulbs, acc. (26)
|Lamp type||Luminous flux in [lm]|
|light bulb||25 W||40 W||60 W||75W||100W||150W|
|LED bulb||6 W||8 W||12 W||18 W||22 W||33 W|
Importantly, the spectral analysis of LED lamp radiation shows that even the lamp low color temperatures have in their spectrum quite a significant share of the so-called blue light or visible light with wavelengths of 400-500 nm. According to Behard-Cohen et al. (27) and Sasseville and Hebert (28), it is possible the influence of the LED sources light on the course of human biological rhythm, because waves 450-480 nm show maximum effectiveness in inhibiting melatonin production. There are also reports that blue light may contribute to age-related macular degeneration (AMD) (29). Most literature reports and even the official position of the European Lamp Companies Federation (CELMA) (29) qualifies LED white light to a group that does not pose hazards to the eye (if used correctly), with the exception of some cool-white LEDs whose blue light hazard can be classified as a moderate risk group. In addition, despite the declarations of many manufacturers, LED lamps are environmentally friendly due to clean, compatible production with the RoHS directive (which means no harmful and dangerous substances, ie: lead, cadmium, mercury), there have been reports (30) that LED sources contain certain amounts of heavy metals (Cu, Ni, Cr, Pb, Sn), which in the case of increasing the amount of waste may pose a threat to the environment.
Lighting in areas habitable by humans has a useful value, but it can also be a reason for certain health consequences. Harm reduction caused by incorrect lighting is possible obeying by the following rules:
1. Proper lighting is the illumination chosen in terms of quantity and qualitative to the degree of difficulty of visual work and to current psychological needs and individual limitations or preferences of the user of the illuminated interior.
2. Due to the use of lighting sources with the appropriate colour temperature, decorative frames and accents, one can create a light atmosphere in the living areas, however, the priority is to create the correct lighting conditions at the teenager’s and children’s learning desks in places of movement and work of people with visual impairments and the elderly. In order to to provide the right lighting conditions in these places, one can ask for help in the selection of light sources and their parameters for customer advisers or people who carry out lighting projects, employees in technical stores, lighting companies or architectural offices.
3. It is necessary to prevent situations of significant underexposure, as well as excessive light in the environment, through thoughtful selection and placement of lighting lamps at home, change of lifestyle that is unfavourable for health or habits regarding the use of light (hours of staying indoors illuminated with artificial light, sleeping with the light turned on, using laptops, smartphones until late at night), the use of protection against light entering the house from the outside (blinds, shutters).
4. It is important to be aware of possible threats to human beings and the environment, associated with the use of modern lighting sources and knowledge of the rules for proper storage of used fluorescent lamps and LED lamps.
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