SAFETY SATURDAY: LIGHT

The sun,--the bright sun, that brings back, not light alone, but new life, and hope, and freshness to man--burst upon the crowded city in clear and radiant glory. Through costly-coloured glass and paper-mended window, through cathedral dome and rotten crevice, it shed its equal ray.

- Oliver Twist, Charles Dickens

Human vision is one of the five cardinal senses with which people navigate their worlds. The ability to see is so essential to normal human functioning that blindness and visual impairment is one of the top ten disabilities among adults and is one of the most disabling conditions among children and adults (Vision Australia, 2019). Human sight is so essential to normal human function that the human visual field has evolved in such a way to coordinate the movements of the eyes with the movements of the hands and the arms (Previc, 1990; Abrams et. al., 1990; Land et. al., 1999), other tools with which we interact with our world. The muscles of the eyes, neck, shoulders and trunk coordinate to maintain human visual fixation and flexibility to look at things around us. Organisms have been able to perceive light as crude stimuli for about 550 million years, and interpretation of colour in vision is understood to have developed roughly 30 million years ago (Bowmaker, 1998). The ability to see is an essential faculty for humans, animals, and other living creatures. Functioning vision allows humans to care for themselves, navigate their communities and physical spaces, use tools and devices, and enjoy the bounty of the world through beauty, art, and day to day life. Functioning vision is essential in learning, working, and in safety, where inappropriately light, dark, glaring, or otherwise abnormally lit tasks, environments, and materials introduce risks to the worker. 

Human sight is the process through which non-ionising radiation in the visual spectrum is detected by the eyes, processed by the visual pathway, and then interpreted into visual images. Visual light is radiation of between 400 to 700nm wavelength, above infra-red radiation and below ultraviolet radiation. Infra-red and ultraviolet radiation may be hazardous in and of themselves, where both may cause burns in excessive and unmitigated dosages, resulting in cancers (Sharma et. al., 2024), eye damage (Hathaway & Sliney, 2016), and other accumulative health effects. Human sight begins with light energy that is generated from a source of illumination. The most easily accessible example of this is the sun, which is the star of our solar system and the source of daytime light on Earth, which revolves around the sun (Galilei, 1632). Human-made sources of light are referred to as Luminaires (Illuminating Engineering Society, 2020), being “a complete lighting unit consisting of a lamp or lamps together with the parts designed to distribute the light, to position and protect the lamps, and to connect the lamps to the power supply.” Light generated from a source of illumination is transmitted from that point of generation to a surface, where the intensity of light falling on a surface is measured in lumens per square meter (Lux), and where depending on the properties of that surface and its medium, some light may be refracted through that medium at an angle, such as in the distortion of an image viewed through a glass of water, and some may be reflected off that surface such as in the glint of light on a gold ring. All light energy reaches the human eye after either travelling directly from a point of generation or after having been reflected off of one or multiple surfaces. 

Light energy reaches the human eye, is collected by the refracting apparatus of the lens of the eye and then directed to the retina, which is covered in cells that are stimulated by exposure to light energy of different wavelengths. The intensity of different wavelengths of light that reach the eye determine the perceived brightness of the light, as well as exciting the retinal cells of the eye in specific proportions that give rise to perceptions of colour. This bulk excitation is then transmitted via the optic nerves of the eyes to the lateral geniculate nuclei and then to the visual cortex of the brain, located at the back of the cortex (Snell, 2010), close to the very top of the neck. The nuclei, cortex, and other parts of the brain process this neurological information into perceived images, which help us make sense of the world in which we live for the duration of our lives, which includes perception of depth, of speed and angles, and of proportion. Human sight is the process by which light radiation in the world around us is transformed into neural impulses which give rise to conscious vision. Thus, threats to human visual function can arise due to damage or changed function of any part of this system: changes to the brain can affect perceived vision without any damage to the eyes, such as following tumours of the optic nerve, nuclei, or corte (Snowden et. al., 2012). Damage to the eyes from ageing, excessive energy exposure, or physical trauma can affect the eyes’ fundamental ability to detect light comprehensibly, such as in the case of cataracts (Allen, 2011), glaucoma (Voelker, 2023) or any disease or damage that affects the lens, the iris, the retina, and / or the health of cells in the eye (Watkins, 2003). Human vision changes naturally with age (Schieber, 2006), and so visual faculties will change as a result of time, genetic predisposition, and non-occupational factors such as diet, lifestyle, and other exposures. 

Human sight and visual perception relies on the functioning of the brain, the visual nerves and cortex, and the structural integrity of the eyes. Broadly, protecting the functioning of all of these parts is outside of the reasonable remit of the workplace, aside from ensuring that the brain and eyes of the worker are not damaged physically. Appropriate lighting is essential to allow safe movement around the workplace and to allow workers to perform their job without having to adopt awkward postures or strain their eyes to see (Safe Work Australia, 2011; 2018), as well as working comfortably in designed environments with a minimum of strain (Work Safe Victoria, 2024). AS/NZS 1680.1:2006 provides a summary of recommended illuminances for different activities as shown below in Figure 1, and while this recommendation is useful, inappropriate lighting (Either too much or too little) may have other adverse health effects more generally, potentially increasing the risk of breast cancers (Stevens et. al., 2014), headaches (Friedman & Der Ver Dye, 2009), fatigue and inattention (Fang et. al., 2022) potentially increasing the risk of errors and mistakes, eye strain (Knave, 1984), and mood (Veitch & Newsham, 1998; Safe Work Australia, n.d.) which may cause or exacerbate psychological issues such as anxiety, stress, or depression (Safe Work New South Wales, n.d.). Inappropriate or inadequate lighting can also be antecedent to physical discomfort in the neck and back, where, if the light is inappropriate, a worker will change their posture to better focus their vision on the work being done (Kamalinia et. al., 2013). 

Figure 1

AS/NZS 1680.1:2006 Table 3.1 - Recommended maintained illuminances for various types of tasks, activities or interiors

Note. Retrieved from AS/NZS 1680.1:2006 Table 3.1 - Recommended maintained illuminances for various types of tasks, activities or interiors.

Working environments are lit from sources of natural light such as direct and reflected sunlight, as well as artificial light-sources such as lamps and globes (Comcare, n.d.). Light can also be generated from incandescent sources, where solids or liquids emit radiation as visible light, such as in hot metal or when something is burning. Light sources may also be adjustable in terms of their intensity, to accommodate personal or procedural sensitivity or to avoid interfering with light from other sources (Worksafe Victoria, 2024). Light can also be generated from tasks that involve electrical exchange, metal contact, or high friction, such as welding (Rau et. al., 2017). Light is generated from computer screens (Coles-Brennan et. al., 2019), headlamps (Iacomussi et. al., 2017), and these exposures are sustained for the duration of a shift (Beeson et. al., 2024). Managing workplace, workspace, and work task lighting requires consideration of the worker, their task, and the contribution of natural, artificial, and incidental light sources. 

Figure 2

Adjustable skylights in warehousing in combination with Halogen area lighting.

While the AS/NZS standard provides baseline recommendations regarding space illumination, there are some issues with implementing these recommendations. First, area illumination is a combination of natural and artificial lightsources which, depending on the colour, quality, and intensity of light, may cause interferential glare, contrast, or confusion when the net result of this illumination meets the eyes of the worker. Natural light may be eliminated by drawing blinds and shuttering windows, but the absence of natural light from occupational spaces may have negative psychological effects (Tomassoni et. al., 2015; Meng et. al., 2020; Beute & de Kort, 2014). When considering the workspace, while the luminance of walls and cubicles may be controlled, different windows, tasks, and images shown on screens may have different brightnesses and so impose dynamic visual strain (Wolska & Śwituła, 1999; Hamedani et. al., 2020). Similarly, contrasting environmental colours like different walls, flooring, and design patterns can induce visual fatigue from comprehension, and if environmental colourations correspond to worksite information like hazard areas or control zones (Wise & Wise, 1988). Adherence to the AS/NZS standards are useful starting points but the net effect of area lighting, colour, and space design will depend on the viewer’s personal, cultural, and attentional state (Rodemann, 1999). Secondly, the AS/NZS standards are guidelines and not enforceable unless the design or working plan of that building or space writes conformance to standards into their operating procedures, which typically isn’t done in small scale workspaces or those which have been converted from residential buildings without re-evaluation of lighting and working conditions. Buildings are designed to serve their purposes, and a home will require different lighting compared with an office. This has implications for the risk control of home working environments, where the duty of care may be poorly defined between employer and employee. Additionally, at least in Australia, there are many commercial premises that were originally residential homes, like offices, consulting rooms, GP practices, and dentistry studios. Guidelines for the construction of healthcare facilities are available from the Australasian Health Infrastructure Alliance (AHIA) (AIHA, n.d.) but the applicability of these guidelines to smaller operators is not clear due to scalability, and are couched as considerations, recommendations, or questions, for example (Practice Assist, 2017). Similarly, there are many healthcare practices that are colocated with other businesses - a massage therapy studio in a gym is an example, where different illuminances will be needed across different working spaces. This is to say nothing of the number of workers that want to work from home (Australian Institute of Health and Welfare, 2023). Small and medium-sized enterprises may work from residential, non-renovated commercial, or shared workspaces. This doesn’t even touch the notion of co-working spaces where, by virtue of the single shared working environment, workspace and task-specific lighting risk control is increasingly difficult, especially where the worker is hotdesking. Lastly, these standards recommend general guidelines which satisfy the 95% use-case hypothetical, and so may not meet the needs of workers who are already vision impaired, neurodivergent, or otherwise experience issues with lighting at these levels. Workers are individuals, and so may respond differently to particular arrangements of light, colour, and sound. Where workers can embellish, personalise, or otherwise adjust elements of their environment to suit their personal tastes, their performance, retention and happiness improve (Augustin, 2004; Heitavirta; 2024), this includes adjusting the lighting, arrangement, colour, and space design of their workplaces where this is possible. 

Inappropriate lighting may cause issues resulting from strain, glare, and contrast, especially when working at night or when workplaces may be naturally dark (Safe Work New South Wales, n.d.). While statistics reporting injuries and outcomes owing to eyestrain are poorly recorded, a 2020 survey reported that 32% of young Australians (18-34) believe blue light from computers and smartphones is an issue for their eyesight; 43% of Australians are worried about developing or worsening short-sightedness from too much screen time (Optometry Australia, 2020). The 2022 Vision Report noted that close-focus is a contributing factor for the development of myopia (Optometry Australia, 2022), and close-focus may be a consequence of poor area lighting. The 2022 report also noted that only 11% of respondents took breaks to minimise sustained focus, and 86% of Australians have experienced sore or tired eyes due to their screen use and 78% report having experienced sore or tired eyes from using a computer or tablet during work. These statistics concern the association of sustained device usage with eyestrain, and do not consider area lighting. The effect of eye strain caused by inappropriately low light may be worsened by increased visual load caused by intense visual tasking (Iwasaki & Kurimoto, 1988; Vertinsky & Forster, 2005), which may contribute to stress and anxiety (Seppala, 2001). In technology professionals, the inability to adjust the distance of monitors from viewers, or to change the brightness, glare, and contrast of those screens are found to be predictors of digital eye strain (Zayed et.al., 2021) and musculoskeletal complaints (Wiholm et. al., 2007). Where a worker’s environment is inappropriately lit, accommodational eye movements are increased, contributing to visual fatigue along with blink rate and frequency, which may be means by which a worker attempts to continue engaging with their task in spite of discomfort (Hamedani et. al., 2020). Glare and shadows in workspaces need to be minimised to decrease the light contrast to which workers must adapt. Lighting solutions in offices and workspaces also need to take the time of day into account. Where lighting surveys are undertaken, the contribution of daylight or its absence to the illumination of the environment must be factored into a lighting solution, firstly to arrive at an accurate measurement of illumination, secondly to account for the movement of the sun throughout the day, thirdly to assess the movement of any reflected or glaring light, and lastly to account for the presence or absence of light to support a worker’s mood (Smith, 1991).

Managing lighting in the workplace is a dynamic challenge that requires consideration of the worker, the work, the workspace, and time. Poor or inappropriate physical environments are recognised as threats to worker mental health, where conditions that affect concentration, uncomfortable conditions, and inappropriate work-related accommodations are recognised as psychosocial hazards (Safe Work Australia, n.d.). Management of lighting and environmental concerns should be undertaken in line with the Hierarchy of Controls (Safe Work Australia, 2018). Following consultation with workers and an assessment of the working environment which may include work observation, lighting issues can be solved with engineering, isolation, and administrative adjustment depending on the task. For light exposure as a consequence of job task like in welding or in dental work, worker PPE may be effective in minimising risk as light exposure is a ubiquitous element of the job design. Where workers are working in inappropriately lit environments, lighting should be reviewed to best illuminate work stations and work areas, or task-specific lighting should be provided. Lighting in offices should consider the nature of the work, duration, the amount of light and how that changes throughout the day. In general, good lighting should allow employees to easily view their work and environment without straining their eyes, understanding that visual demands of the work will determine the lighting needs of an area. The quality of light will depend on the number of lights in use, whether LED, fluorescent or other lights are used, fittings that direct light, and the effect of light on the colour of other surfaces. Glare, reflections, shadows and visual adjustments should be assessed through consultation with workers and observation of tasks. Glare can be minimised by eliminating incident light. Reflections can be minimised by using materials with low reflectance. Shadows can be eliminated by redirecting light or providing backlighting. Postural assessments should also be undertaken to ensure that inappropriate compensatory adaptations are not being used to manage visual strain from inappropriately low light or inappropriately glaring or reflective surfaces. Lastly, this ecosystem of intervention should be reviewed year-round as the seasons, time of day, duties of work, and spatial arrangement of the work area changes. These measures may also require adjustment based on the worker - their age, medical status, and preferences. The worker should be given the opportunity to provide input into the management of their working environment, to improve consultation power, and to improve the relationship between that worker and their employer to develop organisational rapport. 

The ability to see is fundamental to human function. Humans and workers need functioning eyes, appropriate illumination, and tolerable conditions to live their lives comfortably, go about their work productively, and to manage safely through the day and across time. Managing appropriate illumination in workspaces and workplaces requires consideration and balance of natural and artificial sources of light, of management of personal and occupational variances, and of course the awareness of change. Human vision and eyesight change as life progresses, and workers will need appropriate levels of support to accommodate and illuminate their work so as to keep them safe, in good health, and support their dignity of life. As inevitable as the rising and falling of the sun, so to is it essential that workplaces, workspaces, workers, and work support the health, wellbeing, and sustainable participation of the worker in their lives.

None of this information constitutes medical, legal, occupational health and safety, best guidance, standard, or other guidance, instruction, or prescription. 

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