It’s time to stop working in biological darkness

Part 2 of a 4-part series on lighting for health and well-being

Ideally, we should be getting a good strong dose of bright blue light for a couple of hours in the morning, when we need to be up and at ’em, and dimmer, warmer (non-blue) light in the evening, when we’re getting ready to conk out.

For many of us, however, our days bring just the opposite. Traditional office lighting tends to be too dim and warm, delivering an insufficient amount of the blue light we need in the morning. Computer and television screens and cell phone displays, on the other hand, tend to be saturated with blue light—the last thing we need at night, especially in the hours just before bedtime.

In effect, this means that many of us work in biological darkness during the day, then experience biological daylight during the night. No wonder our body clocks get out of whack!

Melanopic lighting with tunable LED luminaires

Don’t blame building owners and office managers for not taking the melanopic effect of light into account. The melanopsin system in the human eye and brain wasn’t discovered until the late 1990s, and the dynamic LED lighting systems that are capable of delivering illumination strategies based on an understanding of melanopic light weren’t up to the task until around 2010.

With the tunable LED luminaires and software-based controls available today, however, delivering melanopic lighting experiences in offices is a piece of cake.

Tunable LED luminaires allow you to select the exact shade (color temperature) of white light you need, from warm to cool, and to change it whenever you like. More sophisticated LED luminaires are actually spectrally tunable—meaning that you can make minute adjustments to the entire spectrum of light that they produce, amping up certain wavelengths while damping down others.

With timeline-based controls, you can “set and forget” lighting scenes that slowly change over the course of the workday. Research-based lighting “recipes” are intended to deliver the optimum light for supporting the circadian well-being, happiness, and even productivity of the employees in illuminated spaces.

Experimental support for melanopic lighting

At the 2nd International Workshop on Circadian and Neurophysiological Photometry in 2019, participating researchers and scientists created a set of recommendations on how best to support human physiology in day-active people within indoor settings.

These recommendations called for bright days and dim nights—not for visual reasons, but for non-visual ones associated with the eyes’ melanopsin-based photoreceptors. Adjusting lighting to optimize daytime, evening, and night exposure to light at different wavelengths and intensities may increase performance, focus, and well-being. Workplace lighting designs should include maintaining regular circadian patterns in employees as an important aspect of office ergonomics.

A randomized controlled trial conducted in 2008 demonstrated the potentially beneficial effects of variable lighting intensities and color temperatures on workplace mood. Pulses of bright light (5,000 lux) were observed to potentially relieve subjective symptoms of distress and improve the mental state, alertness, and performance of shift workers.

These are just two of the dozens of studies done on the melanopic effect of lighting on people in office environments. It’s fair to say that melanopic lighting is now an established and increasingly adopted approach to office lighting design and specification.

Measuring melanopic light

In recent years, the lighting industry has been in search of standard measurements that designers can use to ensure the proper levels of melanopic lighting in different circumstances. As with many emerging standards, competing metrics have been proposed.

The two most widely adopted have been melanopic equivalent daylight illuminance (m-EDI) and equivalent melanopic lux (EML). Both metrics are intended to quantify the amount of light most responsible for affecting the human circadian rhythm—that is to say, the amount of light in and around the blue portion of the visible light spectrum (technically speaking, in the region of 480 nm).

The International Commission on Illumination (CIE) supports m-EDI, as does Signify. Without getting into the mathematics, suffice it to say that m-EDI does a better job of quantifying the spectrum of light in combination with its brightness (intensity).

Experts like the CIE, and standards like the WELL Building Standard, can now make recommendations for levels of melanopic lux in offices and other lit environments. The recommendations funded by the 2nd International Workshop on Circadian and Neurophysiological Photometry mentioned above call for 250 melanopic lux or greater during the daytime, and less than 10 melanopic lux in the hours leading up to bedtime. Similarly, the CIE recommends “high melanopic EDI during the day [to support] alertness, the circadian rhythm and a good night’s sleep,” and “low melanopic EDI in the evening and at night [to facilitate] sleep initiation and consolidation.”

Continue reading part 3 of our 4-part series on lighting for health and well-being.

About the author

Peter Duine is Global Subsegment Director for Offices at Signify. He joined Philips 28 years ago as an engineer in the Research Laboratories. Peter moved to the lighting division 16 years ago as an optical engineer, and was a pioneer in developing light engines and drivers as systems for general lighting applications.