EN ISO 24443:2021
(Main)Cosmetics - Determination of sunscreen UVA photoprotection in vitro (ISO 24443:2021, Corrected version 2022-02)
Cosmetics - Determination of sunscreen UVA photoprotection in vitro (ISO 24443:2021, Corrected version 2022-02)
This document specifies an in vitro procedure to characterize the UVA protection of sunscreen products. Specifications are given to enable determination of the spectral absorbance characteristics of UVA protection in a reproducible manner.
In order to determine relevant UVA protection parameters, the method has been created to provide an UV spectral absorbance curve from which a number of calculations and evaluations can be undertaken. These include calculation of the Ultraviolet-A protection factor (UVA-PF) [correlating with in vivo UVA-PF from the persistent pigment darkening (PPD) testing procedure], critical wavelength and UVA absorbance proportionality. These computations are optional and relate to local sunscreen product labelling requirements. This method relies on the use of static in vivo SPF results for scaling the UV absorbance curve.
This document is not applicable to powder products such as pressed powder and loose powder products.
Kosmetische Mittel - In-vitro-Bestimmung des UVA-Schutzes von Sonnenschutzmitteln (ISO 24443:2021, korrigierte Fassung 2022-02)
Dieses Dokument legt ein In vitro Verfahren zur Charakterisierung des UVA Schutzes von Sonnenschutz¬mitteln fest. Es werden Spezifikationen angegeben, die eine reproduzierbare Bestimmung der spektralen Extinktionseigenschaften des UVA Schutzes ermöglichen.
Zur Bestimmung von für den UVA Schutz relevanten Kenngrößen wurde ein Verfahren zur Aufstellung einer Kurve der spektralen Extinktion im UV Bereich entwickelt, auf dessen Grundlage eine Reihe von Berechnungen und Bewertungen vorgenommen werden können. Diese umfassen die Berechnung des UVA Schutzfaktors (UVA PF) [korreliert mit dem In vivo UVA Schutzfaktor aus dem Persistent-Pigment-Darkening (PPD) Prüfverfahren], der kritischen Wellenlänge und des UVA-Extinktionsverhältnisses. Diese Berechnungen sind optional und beziehen sich auf die örtlichen Anforderungen an die Kennzeichnung von Sonnenschutzmitteln. Dieses Verfahren basiert auf der Verwendung von statischen In vivo SPF Ergebnissen für die Skalierung der UV Extinktionskurve.
Dieses Dokument ist nicht anwendbar für pulverförmige Produkte, die z. B. gepresst oder lose vorliegen.
Cosmétiques - Détermination in vitro de la photoprotection UVA (ISO 24443:2021, Version corrigée 2022-02)
Le présent document spécifie un mode opératoire in vitro pour caractériser la protection UVA apportée par les produits de protection solaire. Des spécifications sont fournies pour permettre de déterminer les caractéristiques d’absorbance spectrale de la protection UVA de façon reproductible.
Afin de déterminer les paramètres de protection UVA pertinents, la méthode a été mise au point de sorte à fournir une courbe d’absorbance spectrale UV à partir de laquelle des calculs et des évaluations peuvent être effectués. Ces calculs comprennent le calcul du facteur de protection contre les ultraviolets A (FPUVA) [corrélé au FPUVA in vivo du mode opératoire d’essai de pigmentation persistante (PPD)], de la longueur d’onde critique et de la proportionnalité de l’absorbance des UVA. Ces calculs sont facultatifs et sont liés aux exigences d’étiquetage locales des produits de protection solaire. Cette méthode repose sur les résultats du FPS in vivo statique pour élaborer la courbe d’absorbance des UV.
Le présent document n’est pas applicable aux produits sous forme de poudre tels que les produits en poudre compacte ou en poudre libre.
Kozmetika - Določevanje zaščitnega faktorja UVA in vitro (ISO 24443:2021, popravljena izdaja 2022-02)
Ta dokument določa postopek in vitro za opredelitev zaščite pred žarki UVA varovalnih sredstev za zaščito kože pred soncem. Podane specifikacije omogočajo določitev lastnosti spektralne absorpcije zaščite pred žarki UVA na ponovljiv način.
Za določitev ustreznih parametrov zaščite pred žarki UVA je bila ustvarjena metoda za zagotovitev krivulje spektralne absorpcije UV, iz katere je mogoče izpeljati številne izračune in ocene.
Slednji vključujejo izračun ultravijoličnega A zaščitnega faktorja (UVA-PF) [ki se navezuje na UVA-PF in vivo iz preskusnega postopka obstojne pigmentacije (PPD)], kritične valovne dolžine in razmerja absorpcije žarkov UVA. Ti izračuni so izbirni in se navezujejo na zahteve glede označevanja izdelkov za zaščito kože pred soncem. Ta metoda temelji na uporabi rezultatov in vivo za statični zaščitni faktor pri določanju merila krivulje absorpcije žarkov UV.
Ta dokument se ne uporablja za izdelke v prahu, kot so na primer pudri v kamnu in prahu.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-julij-2022
Nadomešča:
SIST EN ISO 24443:2012
Kozmetika - Določevanje zaščitnega faktorja UVA in vitro (ISO 24443:2021,
popravljena izdaja 2022-02)
Cosmetics - Determination of sunscreen UVA photoprotection in vitro (ISO 24443:2021,
Corrected version 2022-02)
Kosmetische Mittel - In-vitro-Bestimmung des UVA Schutzes von Sonnenschutzmitteln
(ISO 24443:2021, korrigierte Fassung 2022-02)
Cosmétiques - Détermination in vitro de la photoprotection UVA (ISO 24443:2021,
Version corrigée 2022-02)
Ta slovenski standard je istoveten z: EN ISO 24443:2021
ICS:
71.100.70 Kozmetika. Toaletni Cosmetics. Toiletries
pripomočki
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EN ISO 24443
EUROPEAN STANDARD
NORME EUROPÉENNE
December 2021
EUROPÄISCHE NORM
ICS 71.100.70 Supersedes EN ISO 24443:2012
English Version
Cosmetics - Determination of sunscreen UVA
photoprotection in vitro (ISO 24443:2021, Corrected
version 2022-02)
Cosmétiques - Détermination in vitro de la Kosmetische Mittel - In-vitro-Bestimmung des UVA
photoprotection UVA (ISO 24443:2021, Version Schutzes von Sonnenschutzmitteln (ISO 24443:2021,
corrigée 2022-02) korrigierte Fassung 2022-02)
This European Standard was approved by CEN on 17 October 2021.
This European Standard was corrected and reissued by the CEN-CENELEC Management Centre on 16 March 2022.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATIO N
EUROPÄISCHES KOMITEE FÜR NORMUN G
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 24443:2021 E
worldwide for CEN national Members.
Contents Page
European foreword . 3
European foreword
This document (EN ISO 24443:2021) has been prepared by Technical Committee ISO/TC 217
"Cosmetics" in collaboration with Technical Committee CEN/TC 392 “Cosmetics” the secretariat of
which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by June 2022, and conflicting national standards shall be
withdrawn at the latest by June 2022.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 24443:2012.
This document has been prepared under a Standardization Request given to CEN by the European
Commission and the European Free Trade Association.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 24443:2021, Corrected version 2022-02 has been approved by CEN as
INTERNATIONAL ISO
STANDARD 24443
Second edition
2021-12
Corrected version
2022-02
Cosmetics — Determination of
sunscreen UVA photoprotection in
vitro
Cosmétiques — Détermination in vitro de la photoprotection UVA
Reference number
ISO 24443:2021(E)
ISO 24443:2021(E)
© ISO 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 24443:2021(E)
Contents Page
Foreword .iv
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, symbols and abbreviated terms . 1
3.1 Terms and definitions . 1
3.2 Symbols and abbreviated terms . 2
4 Principle . 3
5 Apparatus . 3
5.1 Spectrophotometer specifications . 3
5.2 Calibration of the spectrophotometer . 4
5.3 Calibration of the UV exposure source . 4
5.4 Monitoring of the UV exposure source . 5
5.5 Calibration of the UVA radiometer used to monitor the test sample irradiation . 5
5.6 Substrate/plate . 5
6 Test method . 6
6.1 Outline of the test procedure . 6
6.2 Equipment calibration and validation of test plates . 6
6.3 Absorption measurements through the plate . 6
6.4 Sample application . 7
6.5 Absorbance measurements of the product-treated plate . 8
6.6 Number of determinations . 8
6.7 Determination of initial calculated SPF (SPF ), “C” value, initial UVA-PF
in vitro,0
(UVA-PF ), and UV exposure dose . 8
6.7.1 Determination of initial in vitro SPF (SPF ) . 8
in vitro,0
6.7.2 Determination of “C” value . 8
6.7.3 Determination of initial UVA protection factor before UV exposure (UVA-
PF ) . 9
6.7.4 Determination of the UV exposure dose . 10
6.8 UV exposure of sample plates . 10
6.9 Calculation of UVA-PF of plates after UV exposure of the sample . 10
6.10 Calculation of critical wavelength of plates after UV exposure of the sample . 11
7 Procedure using the spreadsheet in this document .11
8 Product reference sunscreen .12
8.1 Formula S2. 12
8.2 Standard P8 .12
9 Test report .12
Annex A (normative) Calibration of spectrophotometer and plate transmission test .14
Annex B (normative) Radiometer calibration to spectroradiometric irradiance procedure .18
Annex C (normative) Computation values: PPD and erythema action spectra and UVA and
UV‑SSR spectral irradiances .20
Annex D (normative) PMMA substrate plate surface specifications .23
Annex E (normative) Product reference sunscreen formulations .26
Annex F (informative) Statistical calculations .32
Annex G (informative) Definition and examples of valid results/Factor “C” .35
Bibliography .36
iii
ISO 24443:2021(E)
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 Technical Committee ISO/TC 217 Cosmetics, in collaboration with
the European Committee for Standardization (CEN) Technical Committee CEN/TC 392, Cosmetics, in
accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 24443:2012), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— acceptance of moulded and sandblasted PMMA plates, according to specifications described in
Annex D;
— product application fitted to 1,2mg/cm for sandblasted plates;
— description of application gesture according to tested products;
— introduction of a new high UVA PF standard P8;
— introduction of critical wavelength calculation;
— calculation of coefficient "C" accepted from in vivo screening SPF, with specific conditions based on
SEM and percentage of variability, and new range proposed from 0,6 to 1,6;
— limitation of UVA irradiation dose to 36 J/cm .
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 www.iso.org/members.html.
This corrected version of ISO 24443:2021 incorporates the following corrections:
— Formulae (2) and (4) have been corrected;
— in 6.7.2, the significance of SEM has been explained;
iv
ISO 24443:2021(E)
— in A.5.1, the transmission values for sandblasted PMMA plates have been corrected;
— Bibliographic references have been corrected.
v
ISO 24443:2021(E)
Introduction
This document specifies the procedure to determine the ultraviolet protection factor (UVA-PF) of a
sunscreen product using the in vitro UVA-PF according to the principles recommended by the European
Cosmetic and Perfumery Association (COLIPA) in 2011. The outcome of this test method can be used
to determine the UVA classification of topical sunscreen products according to local regulatory
requirements.
Topical sunscreen products are primarily rated and labelled according to their ability to protect against
sunburn, using a test method to determine the in vivo sun protection factor (see ISO 24444). This
rating evaluates filtration of sunburn generating radiation across the electromagnetic UV spectrum
(290 nm to 400 nm). However, knowledge of the sun protection factor (SPF) rating does not provide
explicit information on the magnitude of the protection provided specifically in the UVA range of
the spectrum (320 nm to 400 nm), as it is possible to have high SPF products with very modest UVA
protection (e.g. SPF 50 with a UVA-PF of only 3 to 4). There is a demand among medical professionals,
as well as knowledgeable consumers, to have fuller information on the UVA protection provided by
their sunscreen product, in addition to the SPF, in order to make a more informed choice of product,
providing a more balanced and broader-spectrum protection. Moreover, there is also a demand to
prevent UVA-induced darkening of the skin from a cultural point of view even without sunburn. The
UVA-PF value of a product provides information on the magnitude of the protection provided explicitly
in the UVA portion of the spectrum, independent of the SPF values.
The test method outlined in this document is derived primarily from the in vitro UVA-PF test method as
developed by COLIPA.
vi
INTERNATIONAL STANDARD ISO 24443:2021(E)
Cosmetics — Determination of sunscreen UVA
photoprotection in vitro
1 Scope
This document specifies an in vitro procedure to characterize the UVA protection of sunscreen
products. Specifications are given to enable determination of the spectral absorbance characteristics of
UVA protection in a reproducible manner.
In order to determine relevant UVA protection parameters, the method has been created to provide an
UV spectral absorbance curve from which a number of calculations and evaluations can be undertaken.
These include calculation of the Ultraviolet-A protection factor (UVA-PF) [correlating with in vivo
UVA-PF from the persistent pigment darkening (PPD) testing procedure], critical wavelength and UVA
absorbance proportionality. These computations are optional and relate to local sunscreen product
labelling requirements. This method relies on the use of static in vivo SPF results for scaling the UV
absorbance curve.
This document is not applicable to powder products such as pressed powder and loose powder products.
2 Normative references
There are no normative references in this document.
3 Terms, definitions, symbols and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological 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/
3.1.1
UV
ultraviolet radiation
electromagnetic radiation in the range of 290 nm to 400 nm
3.1.2
UVB
ultraviolet B
electromagnetic radiation in the range of 290 nm to 320 nm
3.1.3
UVA
ultraviolet A
electromagnetic radiation in the range of 320 nm to 400 nm
Note 1 to entry: UVA II = 320 nm to 340 nm; UVA I = 340 nm to 400 nm.
ISO 24443:2021(E)
3.1.4
spectral absorbance
ai(λ)
logarithm to base 10 of the reciprocal of the spectral internal transmittance, ai(λ)=−log10 τi(λ)
Note 1 to entry: In the context of this standard the absorption or transmission of sunscreen is used.
3.1.5
irradiance
I
fluence rate per unit area, expressed in W/m , for a defined range of wavelengths
Note 1 to entry: From 290 nm to 400 nm for UVA + UV-B irradiance; from 320 nm to 400 nm for UVA irradiance.
3.1.6
spectral irradiance
I(λ)
irradiance (3.1.5) per unit wavelength, I(λ), expressed in W/m /nm
Note 1 to entry: Spectral irradiance can refer to PPD testing or SPF testing.
3.1.7
spectrophotometer
equipment for measuring the reflection or transmission properties of a material as a function of
wavelength limited to ultraviolet, visible and short infrared ranges in this document
3.1.8
spectroradiometer
device designed to measure the spectral density of illuminants
3.1.9
radiometer
device for measuring the radiant flux (power) of electromagnetic radiation
3.1.10
product reference sunscreen
reference sunscreen product used to validate the testing procedure
3.1.11
solar simulator
equipment used to simulate the solar irradiance and spectrum
3.1.12
plate
substrate
material to which the test product is to be applied
3.2 Symbols and abbreviated terms
3.2.1
UVA-PF
in vitro ultraviolet A protection factor
in vitro UVA protection factor of a sun protection product against UVA radiation, which can be derived
mathematically with in vitro spectral modelling
3.2.2
SPF
in vitro
in vitro sun protection factor
in vitro protection factor of a sun protection product against erythema-inducing radiation calculated
with spectral modelling
ISO 24443:2021(E)
3.2.3
critical wavelength
CWL
λc
wavelength at which the area under the absorbance curve represents 90 % of the total area under the
curve in the UV region
Note 1 to entry: Calculated from spectral data.
3.2.4
erythema action spectrum
E(λ)
relative effects of individual spectral bands of an exposure source for an erythema response
3.2.5
PPD action spectrum
P(λ)
relative effects of individual spectral bands of an exposure source for a persistent pigment response
4 Principle
The test is based on the assessment of UV-transmittance through a thin film of sunscreen sample spread
on a roughened substrate, before and after exposure to a controlled dose of radiation from a defined UV
exposure source.
Because of several variables that cannot be controlled with typical thin film spectroscopic techniques,
each set of sunscreen transmission data is mathematically adjusted so that the in vitro SPF data yield
the same measured in vivo SPF value that was determined by in vivo testing. As in vivo method can
raise ethical consideration, any alternative SPF method, published as an ISO method, may be used.
Samples are exposed to a specific measured dose of UV radiation to account for the photostability
characteristics of the test product.
The resulting spectral absorbance data have been shown to be a useful representation of both the
width and height of the UVA protection characteristics of the sunscreen product being tested. The
mathematical modelling procedure has been empirically derived to correlate with human in vivo
(persistent pigment darkening) test results.
5 Apparatus
5.1 Spectrophotometer specifications
The spectrophotometer wavelength range shall span the primary waveband of 290 nm to 400 nm. The
wavelength increment step shall be 1 nm.
A spectrophotometer that does not have a monochromator after the test sample should employ a
fluorescence rejection filter.
The spectrophotometer input optics should be designed for diffuse illumination and/or diffuse
collection of the transmitted irradiance through the roughened polymethylmethacrylate (PMMA)
substrate, with and without the sunscreen layer spread on its surface.
The size of the diameter of the entrance port of the spectrophotometer probe shall be smaller than the
size of the light spot to be measured at the sample level (in order to account for stray light).
The area of each reading site should be at least 0,5 cm in order to reduce the variability between
readings and to compensate for the lack of uniformity in the product layer.
ISO 24443:2021(E)
The wavelength should be accurate to within 1 nm, as checked using a holmium-doped filter (see
Annex A). The ability of an instrument to accurately measure absorbance is limited by the sensitivity of
the instrument. The minimum required dynamic range for this methodology is 2,2 absorbance units as
determined according to Annex A.
The maximum measured absorbance should be within the dynamic range of the device used. If
the test measurements yield absorbance curves that exceed the determined upper limit of the
spectrophotometer, the product should be re-tested using an instrument with increased sensitivity and
dynamic range.
The lamp in the spectrophotometer that is used to measure the transmittance shall emit continuous
radiation over the range of 290 nm to 400 nm, and the level of irradiance should be sufficiently low, so
that the photostability of the product is not unduly challenged (a xenon lamp is a convenient solution).
Therefore, the UV dose during one measurement cycle should not exceed 0,2 J/cm .
NOTE A spectrophotometer is used to measure the absorbance properties of the sunscreen on the test
plates. A spectroradiometer is used to measure the spectral energy distribution and intensity of the UV exposure
source or the spectrophotometer during the absorbance measurement of the sunscreen on the test plate.
Coupled with an UV source, the spectroradiometer can give similar results to a spectrophotometer.
5.2 Calibration of the spectrophotometer
The spectrophotometer shall be validated every month by measurements of reference materials.
A three-fold test is required, as described in Annex A:
— dynamic range of the spectrophotometer;
— linearity test of the spectrophotometer;
— wavelength accuracy test.
5.3 Calibration of the UV exposure source
The spectral irradiance at the exposure plane of the UV exposure source that is used for irradiation
(to take into account any photoinstability) shall be as similar as possible to the irradiance at ground
[5] [6]
level under a standard zenith sun . As defined by COLIPA , the reference standard sun has a total
2 2
irradiance of 51,4 W/m to 63,7 W/m and a UVA to UVB irradiance ratio of 16,9 to 17,5.
Therefore, the UV irradiance shall be within the following acceptance limits (measured at sample
distance).
Table 1 — UV exposure source specifications
UV exposure source specifications as measured with a spectroradiometer
2 2
Total UV irradiance (290 nm to 400 nm) 40 W/m to 200 W/m
a b
Irradiance ratio of UVA to UVB 11-22
a
320 nm to 400 nm.
b
290 nm to 320 nm.
In broad-beam UV-sources, spectra from different locations under the beam shall be recorded over at
least 5 different locations (a location is defined for each plate) in order to account for uniformity.
The uniformity shall be ≥ 90 % as calculated by Formula (1):
U = (1-(max-min)/(X̅)) (1)
ISO 24443:2021(E)
where
U is the uniformity in percentage;
X̅ is the average.
If the uniformity is less than 90 %, then optical components should be adjusted or appropriate
compensation for different irradiance shall be made in the exposure time on each plate.
The UV exposure source device should have the ability to maintain samples within the range of
27 °C (±2 °C) to 32 °C (±2 °C). It is important that the temperature of the sample itself on the plate
shall be measured and not just the surrounding air temperature. Therefore, the measurement of the
temperature shall be on plate level.
To maintain samples at required temperature, a filter system that particularly reduces infrared
radiation shall be used to achieve the specified temperature range. Cooling trays for the sample plates
or ventilators shall be used to maintain a temperature lower than 32 °C (±2 °C) and warming devices to
maintain samples at or above 27 °C (±2 °C).
Measurement should be made using a sensor that is traceable to a national or an international
calibration standard, within the range of use.
5.4 Monitoring of the UV exposure source
The emission of the UV exposure source used for exposure shall be checked for compliance with the
given acceptance limits by a suitably qualified expert (at least) every 12 months, or 2 500 h of lamp
running time. The inspection should be conducted with a spectroradiometer that has been calibrated
against a standard lamp that is traceable to a national or an international calibration standard. In
addition to the spectroradiometric inspection, the intensity of the UV exposure source used for
exposure shall be checked prior to each use.
This can be done using either a spectroradiometer or a radiometer with sensitivity in the UVA,
calibrated for the same UV exposure source spectrum used for the exposure step of the procedure,
applying the coefficient of calibration to adjust for variance between the UVA radiometer and the
reference spectroradiometer.
5.5 Calibration of the UVA radiometer used to monitor the test sample irradiation
If a UVA radiometer is used, this device shall be suitably calibrated. This requires that it is calibrated
with the UVA irradiance measurement results of the spectroradiometer used to measure the exposure
source (as during annual solar simulator calibration).
Calibration shall be conducted in terms of UVA irradiance (320 nm to 400 nm) in accordance with
Annex B and shall be at the same level at which the test plates are exposed. Once calibrated with the
spectroradiometer, the UVA radiometer may be used to determine the UV doses to be used during the
exposure procedure on a day-to-day basis.
5.6 Substrate/plate
The substrate/plate is the material to which the test product is to be applied. For this method, PMMA
plates with one rough side of the substrate shall be used and are commercially available. The size of the
substrate should be chosen such that the application area is not less than 16 cm .
[17][18]
The specifications and preparation of this type of plate are described in Annex D.
ISO 24443:2021(E)
6 Test method
6.1 Outline of the test procedure
6.1.1 Conduct the calibration and validation of the test equipment, including the spectrophotometer
used for transmission/absorbance measurements and the UVA radiometer (or spectroradiometer)
used to measure the UV exposure source. Verify the transmission properties of the test plates batch as
described in Annex D.
®1)
6.1.2 Conduct blank measurements of a glycerin-treated or Vaseline treated plate for the reference
“blank”, which will be used in the subsequent absorbance measurements.
6.1.3 Conduct in vitro absorbance measurements of the sunscreen product spread on a PMMA plate,
prior to any UV irradiation. Acquire the initial mAF spectrum with A (λ) data, where mAF (=10^A)
6.1.4 Conduct the mathematical adjustment of the initial UV absorbance spectrum using coefficient
“C” [see Formula (2) the calculation in 6.7.2] to achieve an in vitro SPF (no UV dose) equal to the
measured static in vivo SPF. Initial UVA-PF is calculated using A (λ) and C. A single UV exposure dose,
0 0
D, is calculated, equal to 1,2 × UVA-PF in J/cm , for each plate.
6.1.5 Conduct UV exposure of the same sample as in 6.1.3, according to the calculated UV exposure
dose D.
6.1.6 Measure the in vitro absorbance of the sunscreen product after UV exposure. Acquire the
second UV spectrum with A(λ) data.
6.1.7 Conduct the mathematical adjustment of the second mAF spectrum (following UV exposure)
by multiplying with the same coefficient “C”, previously determined in 6.1.4. The resulting absorbance
curve is the final adjusted absorbance values.
6.2 Equipment calibration and validation of test plates
Test procedures as described in Annex A are to be completed to validate the wavelength accuracy,
linearity and absorbance limits of the spectrophotometer/spectroradiometer to be used for the test
procedure. Validation of the UV properties of the test PMMA plates batch shall also be conducted as
described in Annex D.
6.3 Absorption measurements through the plate
It is necessary to first determine the absorbance of UV radiation through a “blank” PMMA plate. ®
Prepare a “blank” plate by spreading a few microlitres of glycerin/Vaseline on the roughened side ®
of the plate. Choose the amount of glycerine/Vaseline such that the entire surface is just completely
covered (approximately 15 μl for a 50 mm × 50 mm plate). ®
Any excess of glycerine/Vaseline should be avoided. Measure the absorbance through this “blank”
plate and use this as the baseline measurement for subsequent absorbance measurements.
Measurements shall be performed on same type of plate as the one used for the product (moulded or
sandblasted) and same batch.
NOTE Many spectrophotometers have “baseline” functions to automatically incorporate this baseline
measurement into the calculations of subsequent absorbance measurements. ®
1) Vaseline is an example of a suitable product available commercially. This information is given for the convenience
of users of this document and does not constitute an endorsement by ISO of the product named. Equivalent products
may be used if they can be shown to lead to the same results.
ISO 24443:2021(E)
6.4 Sample application
The sunscreen product is applied to a new untreated roughened PMMA plate (with the roughened side
2 2
uppermost) by mass, at an application rate of 1,3 mg/cm (±1,6 %) for moulded plates and 1,2 mg/cm
(±1,5 %) for sandblasted plates.
To ensure dose accuracy and repeatability, the application area should be not less than 16 cm .
The application dose may be determined by measuring the mass loss of the pipette before and after
application of the product; alternatively, it may be applied based on volumetric measurements with
consideration of the specific gravity of the test sample. Where possible, a positive-displacement
automatic pipette should be used for this purpose.
Plates should be weighed after application phase for any non-volatile product.
The sunscreen is applied as at least twelve small droplets of approximate equal volume, distributed
evenly over the whole surface of the plate.
Finger cots should not be used to spread the product on the plate.
The fingertip used for spreading shall be dipped into the test product and then wiped to remove excess
product before spreading the test product applied to the plate. The fingertip used to spread the product
shall be cleaned between applications of different test products.
Deposit and weighing shall not take more than 30 s.
The first test plate applied should not be used for all the measurements, but to adjust the quantity.
After the sunscreen product is deposited on the surface of the plate, it shall be spread immediately over
the whole surface using light strokes with human fingertip or mechanical fingertip.
Spreading should be completed in a two-phase process:
First, the product should be spread on the whole area of the plate, using circular movements with a
minimum of four passages from the top to the bottom of the plate. At the end of the first pass, a turn
of the plate has to be done (¼ turn) to alternate passages, with minimal pressure and repeat this
movement three times at least (about 30 s).
Then the sample should be rubbed on the plate surface using alternating horizontal and vertical strokes
repeated at least three times alternate passages with a moderate but increased pressure. The second
phase should last about 30 s with increased moderate pressure.
For alcoholic or oil products, application should be adapted as follows:
First, the product should be spread on the whole area of the plate, using circular movements with
a minimum of three passages from the top to the bottom of the plate. At the end of the first pass, a
turn of the plate has to be done (¼ turn) to alternate passages, with minimal pressure and repeat this
movement two times at least (about 20 s to 25 s).
Then the sample should be rubbed on the plate surface using alternating horizontal and vertical strokes
repeated at least two times alternate passages with a moderate but increased pressure. The second
phase should last about 20s with increased moderate pressure.
For all kinds of products, the treated sample shall be allowed to dry for 30 min to 60 min in the dark
at the same temperature under UV exposure conditions (i.e. if UV source exposure conditions will be
30 °C, then the drying conditions should also be at 30 °C; or if the UV source exposure conditions will be
27 °C, then the drying conditions should also be 27 °C).
Spray products provided in a pressurized container shall first be degassed by puncturing a very small
pinhole in the container to relieve all of the pressure, and then allowed to rest for at least 24 h at room
temperature before accessing the liquid for testing.
ISO 24443:2021(E)
6.5 Absorbance measurements of the product‑treated plate
The product-treated plate is placed in the light-path of the spectrophotometer and the absorbance of
UV radiation through the sample is determined for each wavelength, from 290 nm to 400 nm, in 1 nm
steps. One or more observations of absorbance may be made per plate and the mean value shall be
determined for each plate.
6.6 Number of determinations
At least four plates prepared with the test sunscreen shall be used to establish the protection aspects of
the test sample. Additional plates shall be added to the sampling if the 95 % confidence interval (CI) is
greater than 17 % of the mean value of the UVA-PF value, until the 95 % CI is less than 17 % of the mean
UVA-PF value. Calculation procedures for this are described in Annex F.
6.7 Determination of initial calculated SPF (SPF ), “C” value, initial UVA‑PF
in vitro,0
(UVA-PF ), and UV exposure dose
6.7.1 Determination of initial in vitro SPF (SPF )
in vitro,0
The UV solar simulator radiation source spectrum, I(λ), (see Annex C) is multiplied with the
corresponding erythema action spectrum sensitivity value, E(λ), (see Annex C) at that wavelength to
yield the sunburning effective energy at that wavelength. The resulting sunburning effective irradiance
is integrated over the 290 nm to 400 nm range. The sunscreen transmission values at each wavelength
are multiplied with the erythemal effective energy at that wavelength and integrated over the same
interval to yield the effective sunburning energy transmitted through the test product. The ratio of
these two integrals is the in vitro calculated SPF value.
Calculation of SPF is shown in Formula (2):
in vitro,0
λ=400
EIλλ × ×dλ
() ()
∫
λ=290
SPF = (2)
invitro,0
λ=400
−A λ
()
E ()λ ×IId()λλ ××10
∫
λ=290
where
[1]
E(λ) is the erythema action spectrum (see Annex C);
I(λ) is the spectral irradiance received from the UV source (SSR for SPF testing) (see Annex C);
A (λ) is the mean monochromatic absorbance of the test product layer before UV exposure;
d(λ) is the wavelength increment (in step of1 nm).
NOTE This calculated SPF value cannot be used, as an expected SPF, neither as an in vitro SPF result.
6.7.2 Determination of “C” value
The initial absorbance curve values are multiplied by a scalar value “C” until the in vitro calculated SPF
values are equal to the in vivo measured SPF. In vivo SPF can be used from the mean SPF obtained from
screening test (at least 5 valid subjects) or full test (at least 10 valid subjects), measured by a published
ISO method.
Extrapolation from screening is possible if final (full test) has a standard error of the mean (SEM) not
greater than 3,8 and the variability of the in vivo SPF shall not exceed 17 %.
As in vivo method can raise ethical consideration, any alternative SPF method, published as an ISO
method, may be used.
ISO 24443:2021(E)
This is accomplished in an iterative calculation process. The initial absorbance values multiplied by this
“C” value become the adjusted sunscreen absorbance curve that is used for determination of the initial
UVA-PF value, and the exposure dose. Formula (3) shows the calculation of the adjusted in vitro SPF
(SPF ) and determination of the coefficient of adjustment “C”:
in vitro,adj
λ=400
EIλλ × ×dλ
() ()
∫
λ=290
SPF = (3)
invitroa, dj
λ=400
−ACλ
()
E ()λ ×× Id()λλ×× 10
∫
λ=290
where E(λ), I(λ), A (λ) and d(λ) are as defined in Formula (2).
This calculation is based on Lambert-Beer’s law which is related to ideal solutions. While sunscreens in
thin film do not behave as ideal solutions, this calculation has been proven satisfactory for this specific
[10][11]
application .
As for tested product and reference sunscreen products S2 or P8, the “C” value shall lie between 0,6
and 1,6 for valid interpretation, with absorbance curves presenting no distortion (see Annex G). If it is
outside this range, the plate is rejected, and new plate shall be prepared by:
— adaptation of the application procedure, in remaining in accordance with all application
specifications;
— increasing the temperature, in remaining in accordance with all temperature specifications;
— changing the type of plate, in remaining in accordance with all substrate/plate specifications.
6.7.3 Determination of initial UVA protection factor before UV exposure (UVA‑PF )
The initial UVA-PF value is calculated for the purpose of determining the UV exposure dose. It is
calculated in a manner similar to the calculation of the initial SPF .
in vitro,0
The intensity spectrum for a UVA radiation source, I(λ), is multiplied at each wavelength with the
persistent pigment darkening action spectrum sensitivity values, P(λ), to yield the pigment darkening
energy at that wavelength.
The resulting pigment darkening effective irradiance is integrated over the 320 nm to 400 nm ra
...
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