ISO/CIE 17166:2019

Erythema reference action spectrum and standard erythema dose

This document specifies the erythema reference action spectrum, ser(λ), and the standard erythema dose (SED).

Spectre d'action érythémale de référence et dose érythémale normalisée

General Information

• Status: Published
• Publication Date: 20-May-2019
• ICS: 17.180.20 - Colours and measurement of light
• Technical Committee: CIE - International Commission on Illumination
• Drafting Committee: CIE - International Commission on Illumination
• Parallel Committee: ISO/TC 274 - Light and lighting
• Current Stage: 9092 - International Standard to be revised
• Start Date: 22-Oct-2024
• Completion Date: 30-Oct-2025

Relations

• Revises: ISO 17166:1999 - Erythema reference action spectrum and standard erythema dose
• Effective Date: 15-Jul-2017

Overview

ISO/CIE 17166:2019 is an international standard jointly developed by the International Organization for Standardization (ISO) and the International Commission on Illumination (CIE). This document defines the erythema reference action spectrum (ser(λ)) and the standard erythema dose (SED), which are critical parameters for quantifying the biological effects of ultraviolet (UV) radiation on human skin, specifically relating to erythema (skin reddening). Published in 2019, this standard updates and replaces the earlier ISO 17166:1999 | CIE S 007-1998 to reflect the latest scientific understanding and terminology in photobiology and UV dosimetry.

The document addresses the challenge in skin photobiology of accurately measuring effective UV exposure by introducing a spectral weighting function and a standardized dose unit to facilitate consistent measurement and assessment of erythemal UV radiation.

Key Topics

• Erythema Action Spectrum (ser(λ))
  This is a spectral weighting function expressing the varying effectiveness of UV radiation at different wavelengths in producing erythema. The function spans wavelengths from 250 nm to 400 nm, reflecting the strong wavelength dependency of erythema response. The action spectrum is normalized so that the maximum effectiveness equals 1, allowing weighted spectral irradiance calculations.

• Erythemal Irradiance
  Defined as the spectral irradiance of UV radiation weighted by the erythema spectral weighting function. It quantifies the effective intensity of UV radiation causing erythema, expressed in watts per square meter (W·m⁻²).

• Erythemal Dose (Radiant Exposure)
  Calculated as the time integral of erythemal irradiance over the duration of UV exposure, measured in joules per square meter (J·m⁻²). This metric better represents the potential for erythema compared to raw UV irradiance or energy values.

• Standard Erythema Dose (SED)
  A standardized measurement unit equivalent to 100 J·m⁻² of erythemal radiant exposure, introduced to provide a consistent, objective measure of UV erythemal effectiveness. The SED facilitates comparison and communication of erythemal UV exposure levels, bypassing limitations of the Minimal Erythema Dose (MED) which varies by individual skin sensitivity and testing conditions.

• Minimal Erythema Dose (MED)
  Medically defined as the UV dose causing minimal perceptible erythema in a specific individual. Because of its variability depending on skin type, pigmentation, anatomical site, and other factors, the MED is recommended by this standard to be reserved strictly for observational and clinical studies rather than standardized erythemal measurement.

Practical Applications

• UV Radiation Safety and Exposure Assessment
  ISO/CIE 17166:2019 enables accurate dosimetry for assessing risks associated with UV exposure from natural sunlight or artificial sources such as lamps and tanning devices.
• Photobiology Research
  Provides researchers with a standardized basis for evaluating UV effects on human skin, facilitating comparability of photobiological data across studies.
• Public Health and Regulatory Compliance
  Assists regulatory bodies in defining safe UV exposure limits based on the erythemal risk, enabling development of standards for occupational safety, consumer products, and environmental health.
• Lighting and Dermatology Industry
  Supports manufacturers of UV-emitting devices and skincare product developers in measuring and labeling erythemal UV output or protection.
• Environmental Monitoring
  Assists in quantifying the erythemal potential of solar UV radiation for climatology, meteorology, and public advisories on solar exposure.

Related Standards

• CIE S 017: International Lighting Vocabulary
  Defines terminology and expressions associated with lighting and optical radiation, essential for understanding terms used in ISO/CIE 17166:2019.
• Other UV and Photobiology Standards
  Various standards on UV measurement techniques, photoprotective products testing, and occupational UV exposure limits complement this standard.
• ISO/IEC Directives
  Guidelines on the development and maintenance procedures for ISO standards ensure the accuracy, consistency, and international acceptance of standards like ISO/CIE 17166:2019.

By adopting ISO/CIE 17166:2019, practitioners and stakeholders gain a scientifically validated, global framework for measuring and communicating erythemal UV radiation exposure, facilitating better protection of human health against harmful ultraviolet effects.

Standards Content (Sample)

INTERNATIONAL ISO/CIE
STANDARD 17166
First edition
2019-05
Erythema reference action spectrum
and standard erythema dose
Spectre d'action érythémale de référence et dose érythémale
normalisée
Reference number
©
ISO/CIE 2019
© ISO/CIE 2019
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
ii © ISO/CIE 2019 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Concept of erythemal irradiance and dose . 3
4.1 Erythemal irradiance . 3
4.2 Erythema spectral weighting function . 4
4.3 Standard erythema dose . 4
Bibliography . 5
© ISO/CIE 2019 – All rights reserved iii

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
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 www .iso .org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso
.org/iso/foreword .html.
This document was prepared by the International Commission on Illumination (CIE) in cooperation
with Technical Committee ISO/TC 274, Light and lighting.
This first edition of ISO/CIE 17166 cancels and replaces ISO 17166:1999 | CIE S 007-1998, of which it
constitutes a minor revision. The document has been editorially revised as per current ISO rules and
the references have been updated.
Any feedback or questions on this document should be directed to the CIE Central Bureau or to the user’s
national standards body. A complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO/CIE 2019 – All rights reserved

Introduction
The problem of dosimetry in skin photobiology lies in the fact that the ability of ultraviolet (UV)
radiation to elicit erythema in human skin depends strongly on wavelength, encompassing a range
of four orders of magnitude between 250 nm and 400 nm. Thus, a statement that a subject received
−2 4 −2
an exposure dose of 1 J·cm (10 J·m ) of UV radiation conveys nothing about the consequences of
that exposure in terms of erythema. If the radiation source was a UV-A fluorescent lamp, no erythemal
response would be seen apart from in people exhibiting severe, abnormal pathological photosensitivity.
The same dose delivered from an unfiltered mercury arc lamp or fluorescent sun-lamp would result
in marked violaceous erythema in most white-skinned individuals. Consequently, photobiologists have
[1]
long recognized the need to express the exposure as an erythemally weighted quantity .
Recently, the term "minimal erythema dose (MED)" has been used widely as a measure of erythemal
radiation. This is unreasonable because the MED is not a standard measure of anything but, on the
contrary, encompasses the variable nature of individual sensitivity to UV radiation. Variables that affect
the MED include: optical and radiometric characteristics of the source; determinants of the exposure,
such as dose increment and field size; nature of the skin, such as pigmentation, previous light exposure
and anatomical site; and observational factors, such as definition of the endpoint, time of reading after
exposure and ambient illumination.
To avoid further confusing misuse of the term MED, it is proposed that this term be reserved solely for
observational studies in humans and other animals, and that a new term, the "standard erythema dose
(SED)", be used as a standardized measure of erythemogenic UV radiation.
© ISO/CIE 2019 – All rights reserved v

INTERNATIONAL STANDARD ISO/CIE 17166:2019(E)
Erythema reference action spectrum and standard
erythema dose
1 Scope
This document specifies the erythema reference action spectrum, s (λ), and the standard erythema
er
dose (SED).
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
1)
CIE S 017:—, ILV: International Lighting Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in CIE S 017 and the following apply.
ISO
...