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INTRODUCTION
Sun protection products have long protected against sunlight-induced erythema with
the level of performance indicated by the sun protection factor (SPF). Since the SPF
number is influenced primarily by UVB wavelengths, however, it is not necessarily a
sufficient indicator of a sunscreen product‟s protection against UVA exposure.
In recent years, the harmful effects of the UVA wavelengths of sunlight have been
more thoroughly established. With this understanding arose the need, not only for
sun protection products that were effective against UVA wavelengths, but also for a
common test method for measuring UVA protection levels.
In seeking to develop an additional method for the separate assessment of a sun-
screen product‟s ability to protect against UVA exposure, it was agreed that an in vi-
tro methodology should be the goal, provided that such an in vitro method could be
shown to correlate with similar data derived from in vivo methods of determining UVA
protection in human volunteers. In order to achieve this correlation, it was necessary
for the test procedure to also take into account any photo-instability in the tested sun-
screen product.
The method described in the following sections arises from considerable technical
discussion and practical investigation of the dynamics of measuring UVA protection
in vitro. It is supported by extensive „ring testing‟, which established a meaningful
correlation with UVA protection factors (UVA-PF) determined on human volunteers
using the previously published in vivo „Persistent Pigment Darkening‟ (PPD) method.
In their Recommendation of 22
nd
September 2006, on the efficacy of sunscreen
products and the claims made relating thereto (2006/247/EC), the European Com-
mission included a requirement for UVA protection comprising both (a) a UVA-PF of
1/3 the SPF as determined by the in vivo PPD method or an equivalent degree of
protection obtained by any in vitro method and (b) an in vitro Critical Wavelength val-
ue of greater than 370nm, in order to satisfy requirements for broad-spectrum UVB /
UVA protection and associated labeling.
This guideline, therefore, provides detailed guidance regarding the instrumentation
and procedures used in the in vitro method to derive both UVA-PF and Critical Wave-
length values. The information and procedures in the following sections should be
strictly observed to ensure correct and accurate determination of UVA protection by
these metrics.
OBJECTIVE
The objective of this new guideline is to provide a validated in vitro method to deter-
mine the UVA protection of sunscreen products. Precise specifications and descrip-
tions, based on experimental data, are given to enable determination, either as a
UVA-PF or Critical Wavelength value in a reproducible manner, in any laboratory.
Recommendation on use: This in vitro method has been developed and validated
primarily for liquid and emulsion-type sun protection products. It may be possible to
use it for some powder-containing products, although this should be validated on a
product-by-product basis.