Ergonomics of human-system interaction — Part 610: Impact of light and lighting on users of interactive systems

This document provides users of interactive systems with a summary of the existing knowledge about ergonomics considerations for the influence of artificial (electric) and natural lighting of environments on humans other than on vision, with a focus on non-image-forming effects. The document can furthermore be used as guidance on the specification of use environments in consideration of non-visual effects of lighting, also called non-image-forming (NIF) functions. Therapeutic use of light and optical radiation is not part of this document.

Ergonomie de l'intéraction homme-système — Partie 610: Impact de la lumière et de l'éclairage sur les utilisateurs de systèmes interactifs

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REPORT 9241-610
First edition
Ergonomics of human-system
interaction —
Part 610:
Impact of light and lighting on users of
interactive systems
Ergonomie de l'intéraction homme-système —
Partie 610: Impact de la lumière et de l'éclairage sur les utilisateurs
de systèmes interactifs
Reference number
ISO/TR 9241-610:2022(E)
© ISO 2022

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ISO/TR 9241-610:2022(E)
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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  © ISO 2022 – All rights reserved

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ISO/TR 9241-610:2022(E)
Contents Page
Foreword .iv
Introduction .v
1 S c op e . 1
2 Nor m at i ve r ef er enc e s . 1
3 Terms and definitions . 1
4 L ight and lighting — more than just vision . 4
4.1 H ow radiation impacts the human body . 4
4.2 T he role of light for life . 5
4.3 N on-visual effects of radiation . 6
4.4 A n ew definition of lighting . 9
4.5 W hy light is not light and daylight in interiors is different from solar light . 9
4.6 T he role of daylight and solar radiation . 11
5 L ight and circarhythms .11
5 .1 Ba s ic s . 11
5.2 I mportance of light for the circadian rhythm .12
5.3 A n ew perspective on light. 14
5.4 R elation to other zeitgebers. 16
6 L ight at night (LAN) .17
6.1 General . 17
6.2 S tudies of light at night (LAN or ALAN) . 18
7 L ight history (memory effect) .19
8 Phy s ic a l c h a r ac t er i s t ic s .21
8.1 S patial distribution of the source . 21
8.2 L ocation of the source . 21
8.3 L ight spectrum and its role for vision . 22
8.4 L ight spectrum and its role for non-visual effects . 23
8.5 T ime and timing . 24
8.6 I ntensity . 24
8.7 T he role of visual displays . 24
9 I nd i v idu a l d i f f er enc e s .26
9.1 C hronotype . 26
9.2 A ge dependency . 26
9.3 I nternal circadian time (body time) . 27
10 C onc lu s ion s .28
10 .1 A g r e e d f ac t s .28
10 . 2 C ont r over s i a l i s s ue s .28
Annex A (informative) Some useful behaviours of users or beneficial conditions for the
physical environment .30
Bibliography .31
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ISO/TR 9241-610:2022(E)
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bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see
Attention is drawn to the possibility that some of the elements of this document may be the subject of
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This document was prepared by Technical Committee ISO/TC 159, Ergonomics, Subcommittee SC 4,
Ergonomics of human-system interaction.
A list of all parts in the ISO 9241 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at
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ISO/TR 9241-610:2022(E)
ISO 9241-6 was developed to give guidance on the work environment, including lighting to support
vision. Since the discovery of a third sensor in the human eye, ample research has demonstrated
that ocular light exposure, besides supporting visual perception, influences many aspects of human
physiology and behaviour, including circadian rhythms, alertness and sleep, mood, neuroendocrine and
cognitive function.
Users of interactive systems that mostly incorporate at least one visual display are likely to be affected
both by the light generated by their work equipment and by lighting as an environmental factor. New
scientific evidence establishes the fact that light exposure by the work equipment can reach levels of
the same magnitude as ambient lighting .
Lighting has been defined as the use of light for making things visible since the International Lighting
Vocabulary of the CIE was published in 1938. In the 4th edition published in 1987, its definition was
“application of light to scene, objects or their surroundings so that they may be seen”. The role of
lighting has been thoroughly reconsidered in the light of the scientific evidence in the last two decades
so that the internationally acknowledged definition was changed in the last version. The definition
now reads “application of light to a scene, objects, or their surroundings” (E-ilv 17-29-001).
“… so that they may be seen” has been dropped because of the new, additional role of light. It is required
by scientists as well as practitioners that the design of lighting be performed in consideration of
health effects. Currently, “Light and Health” has become a slogan pointing to the new goal. This can
be characterized as considering and supporting human circadian rhythms governed by the circadian
clock. Although such rhythms have been studied for decades, the discovery of molecular mechanisms
controlling them was awarded the Nobel Prize for Medicine in 2017. The illustration by the Nobel Prize
Committee can also serve as a short description for this document: “This clock [circadian] helps to
regulate sleep patterns, feeding behaviour, hormone release, blood pressure and body temperature.
A large proportion of our genes are regulated by the clock.” (Figure 1) .
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ISO/TR 9241-610:2022(E)

Best coordination.
Fastest reaction times.
Highest body temperature.
Highest blood pressure.
Melatonin secretion.
Deep sleep.
Lowest body temperature.
Cortisol release.
Fastest increase in blood pressure.
High alertness.
SOURCE The Nobel Committee for Physiology or Medicine. ‘The 2017 Nobel Prize in Physiology or Medicine’
press release . Reproduced with permission of the copyright holder.
Figure 1 — The circadian clock (also known as the circadian oscillator) and its impacts on our
It should be noted that the first Nobel Prize in Medicine was awarded in 1903 to Niels Ryberg Finsen for
his contribution to the treatment of diseases with optical radiation.
The new role of light has been considered not only by scientists but also by various institutions that
deal with ergonomics, work organization, safety and health. Due to a high variety of sources that can be
of relevance, this document has been prepared on the basis of documents representing the published
outcome of expert evaluations of literature with a good general agreement, although published with a
time difference of more than a decade. This document has been prepared after studying References [1]
and [6] to [11] and the literature reviewed by their respective authors.
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Ergonomics of human-system interaction —
Part 610:
Impact of light and lighting on users of interactive systems
1 S cope
This document provides users of interactive systems with a summary of the existing knowledge about
ergonomics considerations for the influence of artificial (electric) and natural lighting of environments
on humans other than on vision, with a focus on non-image-forming effects.
The document can furthermore be used as guidance on the specification of use environments in
consideration of non-visual effects of lighting, also called non-image-forming (NIF) functions.
Therapeutic use of light and optical radiation is not part of this document.
2 Normat ive references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
correlated colour temperature
temperature of a black body (Planckian) radiator whose perceived colour most closely resembles that of
a given stimulus at the same brightness and under specified viewing conditions
[SOURCE: IEV 723-08-34]
field of biology pertaining to periodic rhythms that occur in living organisms in response to external
stimuli such as photoperiod
phase relationship of the circadian clocks to the zeitgeber
Note 1 to entry: A person’s chronotype is the propensity for the individual to sleep at a particular time during a
24-h period.
biological process that displays an endogenous, entrainable oscillation of about 24 hours
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ISO/TR 9241-610:2022(E)
biological process that displays oscillation of about a solar year
colour rendering
effect of an illuminant on the colour appearance of objects by conscious or
subconscious comparison with their colour appearance under a reference illuminant
[SOURCE: E-ilv 17-22-107, modified — Notes to entry removed.]
colour rendering index
measure of the degree to which the psychophysical colour of an object illuminated by the test illuminant
conforms to that of the same object illuminated by the reference illuminant, suitable allowance having
been made for the state of chromatic adaptation
[SOURCE: E-ilv 17-22-109, modified — Notes to entry removed.]
photoreceptor in the retina containing light-sensitive pigments capable of initiating the process of
photopic vision
[SOURCE: E-ilv 17-22-002, modified — Notes to entry removed.]
part of global solar radiation capable of causing a visual sensation
Note 1 to entry: This definition is used for the purposes of lighting engineering. In physics, daylight is solar
radiation in the range of optical radiation.
[SOURCE: E-ilv 17-29-105, modified — Notes to entry replaced.]
daylight factor
quotient of the illuminance at a point on a given plane due to the light received directly and indirectly
from a sky of assumed or known luminance distribution and the illuminance on a horizontal plane
due to an unobstructed hemisphere of this sky, where the contribution of direct sunlight to both
illuminances is excluded
[SOURCE: E-ilv 17-29-121, modified — Notes to entry removed.]
intrinsically photosensitive retinal ganglion cell
cells in the human retina that are intrinsically photosensitive due to the presence of melanopsin, a light-
sensitive protein
light at night
exposure to artificial light during the dark hours of the day
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ISO/TR 9241-610:2022(E)
radiation within the spectral range of optical radiation
Note 1 to entry: This definition also covers the use of the term in most disciplines, e.g. medicine, chemistry,
radiation within the spectral range of visible radiation
Note 1 to entry: Visible radiation is optical radiation capable of causing a visual sensation directly (see E-ilv 17-
21-003 ).
luminous colour
colour perceived to belong to an area that appears to be emitting light as a primary light source or that
appears to be specularly reflecting such light
[SOURCE: E-ilv 17-22-045, modified — Notes to entry removed.]
luminous intensity
I , I
density of luminous flux with respect to solid angle in a specified direction

I =

Φ is the luminous flux emitted in a specified direction;
Ω is the solid angle containing that direction.
Note 1 to entry: Luminous intensity is measured by candela, which is one of the seven SI base units.
[SOURCE: E-ilv 17-21-045, modified — Notes to entry revised.]
hormone that is produced by the pineal gland
optical radiation
electromagnetic radiation at wavelengths between the region of transition to X-rays (λ ≈ 1 nm) and the
region of transition to radio waves (λ ≈ 1 mm)
Note 1 to entry: The lower end of the range begins in some regulations and standards at 100 nm. The difference is
irrelevant for this document because both λ ≈ 1 nm and λ ≈ 100 nm are in the range of UV-C radiation.
[SOURCE: E-ilv 17-21-002, modified — Notes to entry revised.]
relating to or denoting vision in daylight or other bright light, believed to involve chiefly the cones of
the retina
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ISO/TR 9241-610:2022(E)
photoreceptor in the retina containing a light-sensitive pigment capable of initiating the process of
scotopic vision
[SOURCE: E-ilv 17-22-003, modified — Notes to entry removed.]
display or specification of the monochromatic components of the radiation considered
[SOURCE: E-ilv 17-21-015, modified — Notes to entry removed.]
use environment
generic term for the physical environment where light and optical radiation is present or intentionally
Note 1 to entry: In industrial areas, use environment is called work environment. Since the physical environment
outside the working space is also effective for the items under consideration, the term use environment has been
introduced for the purposes of the ISO 9241 series.
environmental cue, such as a change in light or temperature, that entrains or synchronizes an
organism’s biological rhythms, usually naturally occurring and serving to entrain to the Earth’s 24-h
light/dark and 12-month cycles
Note 1 to entry: From the German “zeit” (time) and “geber” (giver).
4 Lig ht and lighting — more than just vision
4.1 Ho w radiation impacts the human body
Radiation, in general, can generate effects in any material if absorbed by it. Radiation or parts of it
reflected or transmitted do not cause any effect, for example a transparent material does not warm up
independently from the level of energy passing through. Cells, tissues and organisms can be affected by
two different categories of radiation, ionising and non-ionising. The distinction is based on the energy
level of the radiated particles. Light, IR, UV and radio waves belong to non-ionising radiation.
NOTE Extraterrestrial UV radiation capable of ionising does not penetrate the atmosphere, whereas electric
sources emitting similar wavelengths are only used for special purposes and are, therefore, not relevant for this
The relevant parts of the spectrum for this document are light (see Figure 3, Figure 4), (non-ionising)
UV and IR. They can cause a variety of responses after entering the body through three pathways
(Figure 2).
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ISO/TR 9241-610:2022(E)
Source Çakir, G. Tageslichtnutzung und Sonnenschutzmaßnahmen an Büroarbeitsplätzen. Reproduced with
permission of the copyright holder.
Figure 2 — Pathways for the solar radiation
A plethora of biological effects are caused by optical radiation hitting the skin and the eyes. Depending
on the wavelength, energy can penetrate the skin to a different depth. While vision for which light
is responsible is considered in most publications, generating vitamin D is of vital interest for human
health, not only for the bones but also for the communication between cells (see also 4.5).
4.2 The r ole of light for life
Light is part of the radiant energy that fills the universe. Almost all life on Earth has evolved
accompanied by light. No wonder that most living species have developed biological processes as a
response to the natural light, the availability of which is governed by the rotation of the Earth and its
motion around the sun.
Thus, light is central to the biological history of the world, both as a fuel for photosynthesis and as an
environmental signal. As a fuel for photosynthesis light produces all green life from sea level up to the
highest places where plants can survive, but also all tropical coral reefs deep down to where sunlight
carries sufficient energy. As a signaller, light carries much of the information that enables life to adapt
to its environment, and improved ability to receive that information is responsible for numerous
evolutionary adaptations.
The importance of visible-light signalling for humans is demonstrated, for example, by the exquisiteness
of the eye as an optical instrument; the large fraction (half) of the human brain devoted to visual signal
processing; and our extreme dependence on visual technologies . In fact, the human eye is not a
sensor that conveys information from the environment to the brain like the ear; it is part of the brain.
At a very early stage of human history, artificial lighting was developed as one of the first human
technologies. It expands the productive day into non-daylight hours and during the day it expands the
productive space into the non-daylight areas of enclosed spaces. Bringing daylight into built space was
one of the main objectives of architecture for thousands of years. Doing so, daylight was manipulated in
different ways even when the “built” environment was a cave.
For the longest part of history, workrooms were built such that artificial lighting served as an auxiliary
means to the main source, daylight. The availability of fluorescent light changed the architecture of
buildings thoroughly, and it was believed that industrial work could be performed even completely
without daylight. But the current notion is that “since the introduction of electric lighting, there has
been inadequate light during the day inside buildings for a robust resetting of the human endogenous
circadian rhythmicity, and too much light at night for a true dark to be detected; this results in circadian
disruption and alters sleep/wake cycle, core body temperature, hormone regulation and release, and
1) Light in this sense is optical radiation.
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patterns of gene expression throughout the body.” Although in the first half of the 20th century the
light inside buildings was less adequate than now, fewer people spent fewer hours in such environments.
With electric lighting becoming ubiquitous, the daily pattern of the light/dark cycle which existed even
in artificially lit interiors to a certain extent has disappeared or can be shifted to other parts of the 24-h
day depending on working hours or personal preferences. However, it is well-known that the light/dark
cycle incident on the retina regulates the timing of the human circadian system. Disruption of a regular,
24-h pattern of light and dark can significantly affect our health and well-being .
4.3 Non-visual effects of radiation
The solar energy received on the surface of the Earth is part of the radiant energy after being filtered
by the atmosphere. The overall range of wavelengths measurable on Earth extends over a range of
−16 5
wavelengths from 10 m to 10 m (electromagnetic spectrum). Only a limited range of wavelengths of
radiation from 380 nm to 780 nm is considered light by definition in lighting engineering because these
enable the eye to form images by exciting visual sensation, a process called vision. In contrast to these,
some other effects of radiant energy are called “non-visual”.
NOTE There is some confusion in the naming of effects caused by optical radiation other than vision. Since
the 1920s, when disciplines dealing with the impact of “light” on humans became separated, various effects
that did definitely not relate to vision were attributed to photobiology. Thus, some researchers used the phrase
“biological effects” until it was acknowledged that also vision is biological. Before the discovery of the ipRGC
in 2002, NIF effects of light were called "light effects" . The term NIF effect (non-image-forming effect) was
coined by Küller in 1983 to cover effects other than vision. But it is still possible to find expressions like “non-
image-forming (NIF) biological effects of light” in scientific publications.
In many publications, effects mediated by melanopsin-containing or intrinsic photosensitive retinal
ganglion cells in the eye are considered “non-visual”. But the subject matter of Reference [7], “the eye-
mediated non-image-forming effects of light”, suggests that the “ability of optical radiation to stimulate
each of the five photoreceptor types that can contribute to retina-mediated non-visual effects of light
in humans”. If only light in the definition of CIE can stimulate the photoreceptors in the eye to name
“optical radiation” instead is at least confusing.
The effects considered in Reference [7] are limited to circadian effects without circannual effects. The
question is whether circannual effects are not eye-mediated. Are they not non-visual? Currently, there
is not even an agreement on how to spell non-visual.
To avoid further confusion, the word “non-visual” is used as an alternative to “NIF” following the
rationale of Reference [18]. If circadian effects in the sense of eye-mediated events are addressed, this
will be indicated.
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ISO/TR 9241-610:2022(E)
1 gamma rays, X-rays and ultraviolet light blocked by the upper atmosphere (best observed from space)
2 visible light observable from Earth, with some atmospheric distortion
3 most of the

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