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Light and Health

How does light influence human health? It has been two decades ago, when the discovery of a new group of photoreceptors (Intrinsically photosensitive retinal ganglion cells, ipRCG) revealed some key processes of non-visual light effects. Since then, there has been performed plenty of research to find the crucial modifying factors which affect our health, especially concerning lighting properties. 

We are now able to give answers to two critical and important questions: How do we have to modify artificial lighting to improve alertness, wakefulness, performance and mood? There is enough scientific data to say that if increased light intensities (illuminance levels starting at 1000 lux) and higher colour temperatures (minimum 5000 kelvin) are installed, all of the above-mentioned mental and cognitive states will show broad improvement.

In addition, modifying lighting parameters as described, will improve sleep quality during the night and prevent insomnia. A few hours (minimum 3 hrs) exposition to daylight will have the same effect. This intervention will be eminently important for population groups, which are at high risk for (day)light deprivation and a lack of circadian stimuli in general, for example institutionalized or immobile people. For those subgroups, optimized artificial lighting can be considered to play a crucial role in disease prevention.

The second important question to be answered is, which health risks we will be confronted with, regarding visible light in general, but also artificial lighting in particular. Scientific data allows us to give clear recommendations, concerning both, the immediate photochemical retinal hazard caused by short-wavelength light as well as long-term hazards caused by circadian disruption. Brightness and spectral distribution of artificial lighting should be modified and controlled in order to cause as less interruption to melatonin and cortisol secretion as possible. There is increasing evidence for circadian disruption to boost the risks for cancer and other serious diseases. Our growing knowledge of cellular pathways and their sensitivity to light leads to simple recommendations, able to drastically improve long-term health outcomes, especially for circadian disrupted subgroups such as shift workers.

Until now, artificial light was only intended to provide adequate viewing conditions, and for these health aspects, new rules (norms) must first be created. How we can promote health with daylight, which has always been associated with health, and what the new EU standard "EN 17037 Daylighting in Buildings" can do, we report in our next newsletter.

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