DIN Standards Committee Food and Agricultural Products
DIN EN ISO 24443
Determination of sunscreen UVA photoprotection in vitro (ISO 24443:2012); German version EN ISO 24443:2012
In vitro Bestimmung des UVA-Schutzes von Sonnenschutzmitteln (ISO 24443:2012); Deutsche Fassung EN ISO 24443:2012
Overview
This International Standard 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 a UV spectral absorbance curve from which a number of calculations and evaluations can be undertaken. Results from this measurement procedure can be used for other computations, as required by local regulatory authorities. These include calculation of the Ultraviolet-A protection factor (UVAPF) (correlating with in vivo UVAPF 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. Recommended use: This in vitro method has been developed primarily for liquid and emulsion-type sunscreen products. This test method has not been validated for powder products and cannot be applied for these products. 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 the 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. Samples are then 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 on the basis of the best adjustment to in vivo results received during tests on humans. This document has been prepared by Technical Committee ISO/TC 217 "Cosmetics" in collaboration with Technical Committee CEN/TC 392 "Cosmetics". The committee responsible for this standard is NA 057-07-01 AA "Kosmetische Mittel" ("Cosmetics") at DIN.
