Effective radiant flux for non-image forming effects – is the illuminance and the melanopic irradiance at the eye really the right measure?

Research indicates that intrinsically photosensitive retinal Ganglion Cells are not evenly distributed or evenly sensitive throughout the retina. Still, most research looking into non-image forming (NIF) effects uses an integral measured quantity, illuminance or melanopic weighted irradiance, to represent the amount of light at the participants’ eye level. This paper describes a theoretical approach to define the effective radiant flux for stimulating the ipRGCs, taking into account a spatially resolved sensitivity. Research on retinal sensitivity is scares and not yet substantial, but the methodology can easily be adopted when areas of specific sensitivity are set. Preliminary results indicate that, with similar vertical illuminances and spectral power distribution, typical office lighting solutions might have a lower NIF effectiveness than settings with higher luminances in the central part of the field of view. This could explain why research on NIF effects is inconclusive, even though reported lighting conditions are similar

On lamps, walls, and eyes: the spectral radiance field and the evaluation of light pollution indoors

Light plays a key role in the regulation of different physiological processes, through several visual and non-visual retinal phototransduction channels whose basic features are being unveiled by recent research. The growing body of evidence on the significance of these effects has sparked a renewed interest in the determination of the light field at the entrance pupil of the eye in indoor spaces. Since photic interactions are strongly wavelength-dependent, a significant effort is being devoted to assess the relative merits of the spectra of the different types of light sources available for use at home and in the workplace. The spectral content of the light reaching the observer eyes in indoor spaces, however, does not depend exclusively on the sources: it is partially modulated by the spectral reflectance of the walls and surrounding surfaces, through the multiple reflections of the light beams along all possible paths from the source to the observer. This modulation can modify significantly the non-visual photic inputs that would be produced by the lamps alone, and opens the way for controlling-to a certain extent-the subject's exposure to different regions of the optical spectrum. In this work we evaluate the expected magnitude of this effect and we show that, for factorizable sources, the spectral modulation can be conveniently described in terms of a set of effective filter-like functions that provide useful insights for lighting design and light pollution assessment. The radiance field also provides a suitable bridge between indoor and outdoor light pollution studies.Postprint (author's final draft

Does architectural lighting contribute to breast cancer?

OBJECTIVES: There is a growing interest in the role that light plays on nocturnal melatonin production and, perhaps thereby, the incidence of breast cancer in modern societies. The direct causal relationships in this logical chain have not, however, been fully established and the weakest link is an inability to quantitatively specify architectural lighting as a stimulus for the circadian system. The purpose of the present paper is to draw attention to this weakness. DATA SOURCES AND EXTRACTION: We reviewed the literature on the relationship between melatonin, light at night, and cancer risk in humans and tumor growth in animals. More specifically, we focused on the impact of light on nocturnal melatonin suppression in humans and on the applicability of these data to women in real-life situations. Photometric measurement data from the lighted environment of women at work and at home is also reported. DATA SYNTHESIS: The literature review and measurement data demonstrate that more quantitative knowledge is needed about circadian light exposures actually experienced by women and girls in modern societies. CONCLUSION: Without such quantitative knowledge, limited insights can be gained about the causal relationship between melatonin and the etiology of breast cancer from epidemiological studies and from parametric studies using animal models

Short-wavelength enrichment of polychromatic light enhances human melatonin suppression potency.

The basic goal of this research is to determine the best combination of light wavelengths for use as a lighting countermeasure for circadian and sleep disruption during space exploration, as well as for individuals living on Earth. Action spectra employing monochromatic light and selected monochromatic wavelength comparisons have shown that short-wavelength visible light in the blue-appearing portion of the spectrum is most potent for neuroendocrine, circadian, and neurobehavioral regulation. The studies presented here tested the hypothesis that broad spectrum, polychromatic fluorescent light enriched in the short-wavelength portion of the visible spectrum is more potent for pineal melatonin suppression in healthy men and women. A total of 24 subjects were tested across three separate experiments. Each experiment used a within-subjects study design that tested eight volunteers to establish the full-range fluence-response relationship between corneal light irradiance and nocturnal plasma melatonin suppression. Each experiment tested one of the three types of fluorescent lamps that differed in their relative emission of light in the short-wavelength end of the visible spectrum between 400 and 500 nm. A hazard analysis, based on national and international eye safety criteria, determined that all light exposures used in this study were safe. Each fluence-response curve demonstrated that increasing corneal irradiances of light evoked progressively increasing suppression of nocturnal melatonin. Comparison of these fluence-response curves supports the hypothesis that polychromatic fluorescent light is more potent for melatonin regulation when enriched in the short-wavelength spectrum

An Investigation of the Operational and Design Characteristics of Circadian Lighting Systems - Report

This report investigates the operation of circadian lighting systems to gain an understanding of the main design and control characteristics and to promote different objectives for use. Research is guided by asking how color intensity, color temperature and their temporal characteristics are related to the circadian response, and how this knowledge can be utilized when designing and operating lighting systems for indoor environments. This report consists of an extensive literature review and case study application cut short by the impact of the novel coronavirus. The case study takes place in an office space housed on the UNMC campus featuring an installed circadian lighting system capable of changing color temperature and intensity independently. The results of the literature review lead to the understanding of biological impacts of suggested operational patterns for the lighting system. Specifically, the interaction between human physical characteristics as they relate to the current lighting technologies has helped to develop the rational for use of these systems. These biological impacts ultimately aim towards improved occupant attention and well-being in the space. Future investigation and implementation are encouraged to continue advanced analysis of occupant response to varied patterns of operation for this circadian lighting system

Light Res Technol

In addition to stimulating the visual system, light incident on the retina stimulates other biological functions, also referred to as non-visual responses. Among the most notable biological functions are human circadian rhythms, which are bodily rhythms that, in constant darkness, oscillate with a period close to, but typically slightly longer than 24 hours. Twenty-four-hour light-dark patterns incident on the retina are the major synchronizer of circadian rhythms to the local time on Earth. Entrainment of circadian rhythms has been implicated in health and well-being. Light can also elicit an acute alerting effect on people, similar to a "cup of coffee." This review summarizes the literature on how light affects entrainment and alertness and how it can be used to achieve these aims.R01 AG034157/AG/NIA NIH HHS/United StatesR01 OH010668/OH/NIOSH CDC HHS/United StatesT32 AG057464/AG/NIA NIH HHS/United States2019-01-01T00:00:00Z30416392PMC6221201vault:3112

Circadian light

The present paper reflects a work in progress toward a definition of circadian light, one that should be informed by the thoughtful, century-old evolution of our present definition of light as a stimulus for the human visual system. This work in progress is based upon the functional relationship between optical radiation and its effects on nocturnal melatonin suppression, in large part because the basic data are available in the literature. Discussed here are the fundamental differences between responses by the visual and circadian systems to optical radiation. Brief reviews of photometry, colorimetry, and brightness perception are presented as a foundation for the discussion of circadian light. Finally, circadian light (CLA) and circadian stimulus (CS) calculation procedures based on a published mathematical model of human circadian phototransduction are presented with an example

Methods to Evaluate Lighting Quality in Educational Environments

Abstract The current standard for lighting of indoor work places (EN 12464-1) essentially prescribes values of photometric quantities (illuminance, Unified Glare Index, etc.); therefore it does not allow a comprehensive analysis of the luminous environment. In Italy, educational buildings do not always comply with the standard requirements for lighting. Therefore an analysis of their current state is needed and this paper illustrates two methods, developed by the authors, to carry out this investigation: the former is based on the analysis of luminance maps obtained through the HDR imaging technique whereas the latter focuses on the evaluation of non-visual effects of light

Non-Image-Forming Effects of Light : Implications for the Design of Living and Working Environments

Våra ögon är viktiga, inte bara för vårt seende, utan också för att synkronisera vår inre biologiska klocka med dygnets 24 timmar. Den biologiska klockan som styr människors dygnsrytm regleras främst av det mönster av ljus och mörker som vi utsätts för under dygnet.Tidigare trodde man att de klassiska fotoreceptorerna, tapparna och stavarna, var de enda ljuskänsliga cellerna i ögat. På 1980-talet publicerades de första forskningsresultaten som tydde på att det fanns ytterligare en typ av receptor. I början av 2000-talet genomfördes forskningsstudier som tydligt visade att det finns en tredje typ av fotoreceptor som har en viktig roll i att förmedla information om den omgivande ljusmiljön från ögat till ett område i hjärnan som styr den biologiska klockan. Dessa receptorer har en större känslighet för energi i det kortvågiga området av den del av det elektromagnetiska våglängdsområdet som definieras som ljus (380 nanometer - 780 nanometer).Idag tillbringar människor alltmer tid inomhus och vistas mindre ute i dagsljus. Det innebär att vi exponeras för det naturliga dagsljusets dygnsrtytm i lägre utsträckning än tidigare. Det artificiella ljuset på dagens arbetsplatser, i våra hemmiljöer och i andra inomhusmiljöer som vi vanligtvis vistas i under dagen skiljer sig på många sätt från det naturliga dagsljuset utomhus. Belysningsstyrkan är lägre och ljusstrålningen har ett annat spektrum, dvs en annan fördelning av energi vid olika våglängder. Dessutom varierar dagsljuset kraftigt över dagen medan det artificiella ljuset normalt är mer statiskt. Detta leder till viktiga frågor om vilken typ av artificiellt ljus som människor bör vistas i för att få en väl fungerande dygnsrytm och ett välbefinnande.En snabb och omfattande teknikutveckling har gjort att vi idag har tillgång till energieffektiva ljuskällor och avancerad teknik för styrning av artificiell belysning och dagsljus i våra byggnader. Detta har gjort det möjligt att i hög grad anpassa belysningen. Med hjälp av kunskap om hur olika aspekter av den dagliga ljusexponeringen påverkar människor kan vi utforma belysningen utifrån människors fysiologiska och psykologiska behov.Syftet med den här avhandlingen har varit att identifiera faktorer i den dagliga ljusexponering som har en avgöande påverkan på människors hälsa och psykologiska välbefinnande. Frågorna i avhandlingen handlade om vilka ljusförhållanden kontorsarbetande människor normalt vistas i under dagen och över året. Vidare undersöktes om det finns en årstidsvariation i den dagliga utsöndringen av två hormon som påverkas av ljus samt när det gäller psykologiskt välbefinnande och sömn. Dessutom studerades hur människor upplevde ljusmiljön på arbetsplatserna vid olika tidpunkter under året. Dagens krav och rekommendationer på inomhusbelysning baseras huvudsakligen på förutsättningarna för att vi skall kunna se. Eftersom de sk icke-visuella effekterna av ljus till stor del bestäms av den tredje receptortypen, som har en annan känslighet för ljusstrålning, handlade andra frågeställningar om hur ljuset i ett rum bör utvärderas med avseende på de icke-visuella effekterna av ljusexponeringen. Den dagliga ljusexponeringen under de olika årstiderna mättes genom att deltagarna under två-tre dagar varje månad bar två olika mätinstrument. Ett av instrumenten registrerade belysningsstyrkan och det andra instrumentet registrerade mängden strålningsenergi i olika våglängdsområden. Dessutom fick deltagarna föra dagbok över den tid de vistades utomhus. På arbetsplatserna mättes ljusets belysningsstyrka och spektrum på förmiddagen och eftermiddagen vid fem tillfällen under året. Detta innebar också att jämförelser mellan de statiska mätningarna och de kontinuerliga mätningarna med de bärbara instrumenten kunde genomföras. Resultaten visade stora årstidsskillnader i den dagliga ljusexponeringen, både när det gäller nivåer och exponeringsmönster. Dessutom tydde resultaten på att det förekom en årstidsskillnad i ljusstrålningens energiinnehåll i olika delar av spektrum.Frågeformulär och dagböcker användes för att ta reda på om det fanns några skillnader under året beträffande välbefinnande och sömn. Resultaten visade ett högre positivt känsloläge under sommaren, speciellt på kvällen. Vidare observerades längre sömn under vintern i jämförelse med sommar, höst och vår.Vid fem tillfällen under året bedömde deltagarna, med hjälp av ett frågeformulär, hur ljuset i kontorsrummen upplevdes. Resultaten visade att upplevelsen av ljuset skiljde sig åt under året. Dessutom observerades samband mellan känsloläget och upplevelsen av ljuset.Jämförelsen mellan de två metoderna att utvärdera ljusförhållandena i kontorsrummen, med hjälp av bärbara instrument och genom statiska mätningar, visade på skillnader mellan metoderna.Resultaten styrker att det är viktigt att ta hänsyn till de icke-visuella effekterna av ljus vid utformningen av belysningsanläggningar. Detta är speciellt viktigt på platser långt från ekvatorn där det är stora årstidsskillnader i dagsljustillgång. Under stora delar av året sker här en betydande del av den dagliga ljusexponeringen på arbetsplatsen. Baserat på laboratoriestudier har vi idag en god förståelse för de aspekter av den dagliga ljusexponeringen som påverkar icke-visuella effekter av ljus. Det här arbetet har bidragit till att visa hur människor som arbetar i kontorsmiljöer vanligtvis exponeras för ljus i vardagen. Studierna visar också att det finns ett behov att utveckla metoder för att utvärdera ljusförhållandena i verkliga ljusmiljöer med avseende på icke-visuella effekter och att inkludera denna kunskap i krav och rekommendationer för belysning

Ground-based hyperspectral analysis of the urban nightscape

Airborne hyperspectral cameras provide the basic information to estimate the energy wasted skywards by outdoor lighting systems, as well as to locate and identify their sources. However, a complete characterization of the urban light pollution levels also requires evaluating these effects from the city dwellers standpoint, e.g. the energy waste associated to the excessive illuminance on walls and pavements, light trespass, or the luminance distributions causing potential glare, to mention but a few. On the other hand, the spectral irradiance at the entrance of the human eye is the primary input to evaluate the possible health effects associated with the exposure to artificial light at night, according to the more recent models available in the literature. In this work we demonstrate the possibility of using a hyperspectral imager (routinely used in airborne campaigns) to measure the ground-level spectral radiance of the urban nightscape and to retrieve several magnitudes of interest for light pollution studies. We also present the preliminary results from a field campaign carried out in the downtown of Barcelona.Postprint (author's final draft