The effect of insufficient artificial lighting on workers' moods and physiology: Preliminary research

In line with the sustainability issue, the current research related to lighting has been focused on maintaining the health and well-being of the workers, not only for energy saving considerations. This preliminary research observed the effect of artificial light below the recommended illuminance levels for the workplace on the workers' moods and their physiological condition. The researchers employed a quasi-experimental approach by observing the participants' sleepiness state, mood, and physiological condition related to their cortisol levels in the first two and last two hours of their work shift. The research subjects were five male printing workers who worked in the basement of an office building in Sleman Regency, Special Region of Yogyakarta, Indonesia. As the room was below the ground floor, to accommodate their work activities, the employees relied on artificial lighting, complemented by a small amount of natural lighting entering the basement. The lighting was measured on the illuminance level of 250s lx and the CCT of 5000s K. The research revealed that there is no complaint or problem regarding the illuminance level, no effect on the individuals' state of sleepiness, or on their moods. However, the cortisol level tended to decrease faster than the normal circadian curve. Therefore, it is reasonable to conclude that even though 'insufficient' lighting levels can accommodate activities, the physiological condition of the subjects shows different results which indicate a negative increment.