Lighting and health workshop: final report

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Lighting and health workshop: final report

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L i g h t i n g a n d h e a l t h w o r k s h o p – f i n a l r e p o r t

N R C C - 5 0 4 6 4

B r a i n a r d , G . C . ; V e i t c h , J . A .

A version of this document is published in / Une version de ce document se trouve dans: 26th Session of the Commission Internationale de l’Eclairage, Beijing, China, July 4-11, 2007, v. 2, pp. 150-153

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LIGHTING AND HEALTH WORKSHOP — FINAL REPORT

† Thomas Jefferson University, USA / * National Research Council of Canada

1.0 INTRODUCTION

The room was full for the duration of this workshop; over 200 people attended and stayed to 18:00 on the last day of the conference portion of the CIE 26th Session in Beijing. This illustrates the widespread interest in the connections between photobiology and lighting design. The session opened with presentations by Dr. George C. Brainard, summarizing the Division 6 perspective and related fundamental research, and by Dr. Jennifer A. Veitch, summarizing the Division 3 perspective on what is needed to support lighting design based on the principles identified by biomedical researchers and photobiologists. Dr. Brainard, moderated the ensuing discussion.

2.0 FUNDAMENTALS OF PHOTOBIOLOGY (DIVISION 6)

Since the 1980s there has occurred a revolution in our understanding of sensory responses to light by invertebrate and vertebrate species, including humans. Detailed scientific reviews are available elsewhere [1,2,3], including several CIE publications and the literature cited therein [4,4,5,6,6]. Briefly, what is known is that:

• Light and dark signals detected by rods and cones support visual perception.

• Light and dark signals are also detected by intrinsically photosensitive retinal ganglion cells (ipRGCs).

• ipRGCs are distributed across the human retina and appear to integrate irradiance signals without spatial resolution.

• Melanopsin is the molecule that transduces light signals in ipRGCs.

• Signals from ipRGCs transmit information about the presence of light to the suprachiasmatic nuclei of the hypothalamus and other nonvisual nuclei involved in neurobehavioral regulation. One of the best elucidated ocular projections is to the pineal gland by a multisynaptic pathway that regulates the production and secretion of the hormone melatonin.

• Nine separate studies have established action spectra for circadian, neuroendocrine and neurobehavioral responses, using various indicators in different mammalian species (e.g., mouse pupillary light reflexes; human melatonin suppression; monkey ganglion cell depolarization). These are consistent in finding a peak wavelength (λmax) in the range 459-484 nm, which is distinct from

both the scotopic and photopic visual spectral sensitivity functions.

• Light exposures that are higher than those normally specified for visual stimulation can be used to regulate circadian functioning to adjust to new time zones, to shift work, and to treat selected sleep disorders. It has also been used to treat mood disorders such as Seasonal Affective Disorder.

These findings are revolutionary in that they reveal previously unknown processes, but it should not be surprising that the eye is responsible for more than one sensory process. The ear, for example, supports hearing, but also balance and movement.

Much is not yet known, however, about the physiology and functioning of ipRGCs and their associated brain structures:

• Action spectrum results are based on monochromatic light; can these results be extended to polychromatic light?

• What are the roles of rods and cones? How do they interact with ipRGCs?

• Is melanopsin a bistable photopigment that dynamically changes ipRGC wavelength sensitivity?

CIE 2007 Lighting and Health Workshop Report — page 2

• How does prior light exposure influence the sensitivity of this newly characterized photosensory system?

3.0 SUPPORTING LIGHTING DESIGN (DIVISION 3)

Models of lighting quality generally require the integration of individual needs, architecture, and economic dimensions. Current lighting recommendations are based principally on providing adequate light to support visual performance while preventing visual discomfort. In these two domains, much is known. There is great excitement about the possibility of incorporating the new knowledge about lighting and health into lighting recommendations for interiors. Before we may do so, however, lighting practitioners require answers to several questions, some from the biomedical community and some from the lighting design and engineering community. One way to organize these questions is to start with the five "Principles of Healthy Lighting" set out in CIE Publication 158:2004, "Ocular lighting effects on human physiology and behaviour" [4]. The numbers below refer to these five principles.

1. If indeed people would benefit from more light exposure than they currently receive, then designers need more detail concerning the necessary timing, intensity, spectrum, duration, and pattern of suitable light exposure. Furthermore, they need to know whether the light dose needs differ for special populations (e.g., people with environmental sensitivities, visual impairments, or particular chronotypes), and whether or not light dose needs change over the life course.

2. If people require a daily period of darkness as well as of light, how dark need it be? Do we need recommendations for room darkness at night? Would this mean recommending that some products be removed from the market (e.g., clocks and night lights with green or blue LEDs)?

3. Research into action spectra for humans has focused on melatonin suppression and has identified a region between 446 - 477 nm as the peak sensitivity for this response; but is melatonin suppression the only process that matters? Does this spectral sensitivity curve hold for daytime light exposures, when there is no circulating melatonin? What about the suggestion that spectral opponency operates, so that a polychromatic light source could have a different effect versus a monochromatic source? What does the fact that there is a different spectral sensitivity function from that for photopic or scotopic vision mean for metrology?

4. If biologically relevant light is light received at the eye, does that change the perspective of a lighting designer? Do lighting design processes need to change to accommodate this? What are the implications for recommendations and standards?

5. If the effect of a given light exposure depends on the time of day, should our recommended practice documents have time-of-day-specific recommendations?

Light has previously unknown effects on our physical and mental health, and this makes for exciting times for researchers. It may also make exciting times for lighting practitioners, but that is not yet a certainty. We have many more questions than clear answers. Division 3's tasks in the coming years are to examine the scientific evidence, to consider its practical implications, to compare these to current recommendations and standards, and — if necessary — to propose new ways of lighting that are suited to the health needs of specific populations, at specific times, and keeping in balance the concurrent requirements for vision, visual comfort, and all the other lighting quality goals.

4.0 DISCUSSION THEMES

Following these two presentations, a lively discussion ensued, in which four broad themes could be identified.

4.1 Time to Forge Ahead

Some audience members argued strongly that enough is known that lighting practice should begin immediately to incorporate principles of healthy lighting. They noted that there is good agreement between results from various labs (e.g., in the general shape of the action spectra for a variety of neurobehavioral responses), and that there have been several demonstrations of successful application of the principles over the short term (e.g., for shift work adaptation). People in this camp argued that the

CIE 2007 Lighting and Health Workshop Report — page 3

absence of perfect understanding of visual performance did not prevent the pioneers in illuminating engineering from proposing illuminance recommendations that were later modified to take into account new information. They do not want to see caution resulting in the same state of affairs — a laundry-list of research questions — at future CIE Sessions. Some argued that the general shape of the published action spectra offers a good starting point for applications.

Others noted that whether explicitly or not, lighting practice already addresses health and safety issues; for example, there are recommendations for lighting control rooms that imply that operators will be able to safely maintain performance even during night shifts.

4.2 A Note of Caution

Other audience members sounded a note of caution, arguing that to put in place a lighting installation with an implied promise of good health adds greatly to liability for the designer and the supplier of the lighting equipment. If we understand poorly what we are doing, then we may be causing more harm than good; and who would license a lighting practitioner for ensuring health and safety based on our current knowledge? Among the problems identified by people in this group is the lack of precision in current discourse; for example, "shift work" is not a single schedule, but a phrase used to describe a wide variety of different settings and routines of working time. Given what is known about the effects of timing of light exposure, any recommendations need to be very precise — but our current level of knowledge is not yet so precise as that.

4.3 Natural is Better (?)

A recurrent theme was the suggestion that in determining the optimal pattern of light exposure, we ought to focus on daylight variation as the biological norm: a low level dominated by long-wavelength light in the morning, a gradual increase in intensity and in the short-wavelength contribution to midday, and then a diminution with proportionally greater long-wavelength contribution in the evening. One person suggested that light sources that vary in colour as well as intensity over the day would be desirable. Other audience members argued that electric light is an unhealthy component of modern life, and favoured a "back to nature" approach. In response, Dr. Brainard pointed out that life expectancy has increased greatly since our primary activities have moved indoors under electric light; although this is a result of many changes (diet, hygiene, physical risks, etc.), it appears that the indoor environments we have created aren't entirely bad, and aspects of them may be beneficial.

A further complication is the fact that "natural daylight" is not a static quantity. Not only are there diurnal variations, but the variations themselves are dependent on latitude and time of year. Several speakers drew attention to the possibility that "good lighting" may differ from one country to another because of such variations and in addition because of local cultural expectations that have arisen in part because of adaptation to such variations.

4.4 Research Questions

Several audience members identified research questions and issues for further consideration:

• What is the necessary low level of light needed for good sleep? One audience member suggested that this could be a safe place to start with practical applications.

• Should night-time light exposure have limits, even for shift workers? In what applications does the requirement to maintain alertness over-ride the risk of night-time exposure (e.g., nuclear power plant control rooms, versus convenience stores)?

• How can we balance the risk from the blue light hazard (BLH) against possible benefits of increased short-wavelength visible light exposure? Is there an increased BLH at the intensities suggested? • For proposed action spectra for melatonin suppression or circadian regulation, we need to confirm

that the spectra derived from monochromatic light exposures are additive.

CIE 2007 Lighting and Health Workshop Report — page 4

• What is the importance of non-architectural light sources to the overall daily light exposure (e.g., computer monitors, televisions)?

5.0 CONCLUSIONS

At the conclusion of the session, all agreed that here is a domain in which CIE can and should take a leading role, being the only international organization combining the expertise of photobiologists, psychologists, physicians, metrologists, engineers, and designers to increase both the understanding of the fundamentals of how light affects health, but the utility of that knowledge for lighting applications. During the workshop, roles for every CIE Division were identified, with Divisions 6 and 3 being the lead areas. Members of these divisions were directed to consider the topics discussed here, and to bring forward suggestions to their respective Division meetings during the following week.

ACKNOWLEDGEMENTS

Our thanks to Drs. Ann Webb, Marc Fontoynont and David Sliney for proposing this session to the organizers of the CIE Quadrennium program, and particular thanks to Dr. Fontoynont for keeping notes during the workshop that contributed to the writing of this report. Dr. Brainard’s participation in this workshop was supported by the USNC/CIE and the National Space Biomedical Research Institute under NASA Cooperative Agreement NCC 9-58.

REFERENCES

[1] Aschoff, J. (1981). Handbook of Behavioral Neurobiology, Biological Rhythms. New York: Plenum Press. [2] Wetterberg, L. (1993). Light and Biological Rhythms in Man. Stockholm: Pergamon Press.

[3] Lam, R. W. (1998). Seasonal Affective Disorder and Beyond: Light Treatment for SAD and Non-SAD Conditions. Washington, DC: American Psychiatric Press, Inc.

[4] Commission Internationale de l'Eclairage (CIE). (2004). Ocular lighting effects on human physiology and

behaviour (CIE 158:2004). Vienna, Austria: CIE.

[5] Commission Internationale de l'Eclairage (CIE). (2004). Proceedings of the CIE Expert Symposium on Light and

Health (Vol. CIE x27:2004). Vienna, Austria: CIE.

[6] Commission Internationale de l'Eclairage (CIE). (2006). Proceedings of the 2nd CIE Symposium on Lighting and

Health, September 7-8, 2006, Ottawa, Canada. Vienna, Austria: CIE Central Bureau.

AUTHORS

George C. Brainard, Ph.D. Thomas Jefferson University Department of Neurology 1025 Walnut Street, Suite 507 Philadelphia, PA 19107 215-955-7644 (phone) 215-923-7588 (fax)

e-mail: george.brainard@jefferson.edu

Jennifer A. Veitch, Ph.D.

NRC Institute for Research in Construction National Research Council Canada Building M-24, 1200 Montreal Road Ottawa, ON K1A 0R6 Canada tel. +1-613-993-9671

fax +1-613-954-3733