GD — Society for Dermopharmacy

Issue 1 (2006)

Dermokosmetics
Statement by GD - Gesellschaft für Dermopharmazie e.V.
UVA-Protective Performance of Sunscreens

(Cologne, 26.01.2006) Excessive sun exposure damages the skin. The part of the sunlight relevant for this phenomenon lies in the ultra-violet range (UV). First noticeable reaction is sunburn which represents foremost an inflammation of the skin induced by UVB-radiation. But also the development of skin tumors and light dermatoses is causatively associated with the UV light. All the same premature skin ageing, wrinkle formation and the relaxation of the skin's connective tissue is accelerated by sunlight (photo-aging). The long-wave UVA-radiation induces this damage in the first place.

Increasing findings about short- and long-term skin damage by excessive sun exposure entail a rising demand of highly-effective sun protection products [1]. Efficient protective performance is obtained by a combined application of organic, oil or water-soluble ("chemical") and inorganic, insoluble ("physical") UV-filters. Corresponding to a statement by the Bundesinstitut für Risikobewertung (Federal Institute for Risk Assessment) [2] as well as the GD guideline "Dermocosmetic Sun Protection" [3] an adequate protection both in the UVB and UVA range should be ensured at a preferably low UV filter quantity.

Assessment of UV-protection

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The UVB-protection is worldwide consistently indicated as light protection factor (LPF; sun protection factor: SPF). Its determination has been defined in many national standards. As the methods only differ to a minor extent, the protection factors determined are easily comparable. In Europe and several other countries the values are stipulated today according to the International SPF test method [4]. This in-vivo method is a further advancement of a method which has been developed in 1994 by COLIPA, the European umbrella organization of national associations of cosmetics industry. The final point is here unambiguously and relevant defined bout the minimal erythema dose (MED). The consumer is accustomed to this declaration and adheres to it when selecting a product.

The level of the UVA-protection in contrast only plays a minor role so far for the product selection. The orientation by the consumer is here far more difficult as neither the determination of the UVA-protection level nor the pertinent declaration has been regulated standardized.

For the characterization of the UVA-protection a different in-vitro and in-vivo approach is usual at present:

n vivo:

• Lasting direct tan (PPD) [5, 6]
• Instantaneous direct tan (IPD) [7]
• UVA-PPD and UVA-erythema (PFA) [8]

in vitro:

• UVA protection percentage (APP) [9]
• UVA/UVB ratio [10]
• Critical wavelength [11]
• Australian standard [12]

Also methods covering new final points (immunosuppression, DNA-damage) are at present subject to discussion [1, 13, 14], however they must be further developed to that extent that they may serve as standard method.

Farther developed, however, is a procedure at which the free radicals caused by UVA and UVB radiation are measured by means of electron spin resonance spectroscopy based on skin biopsy. From the result of this measurement the so-called integrated light protection factor is calculated which summarizes the UVA and UVB protection of a product in one value [15].

Function of the
Australian standard

Among the outlined methods the Australian standard has at present established as quasi norm. Most producers indicate the UVA protection according to the Australian standard and also most consumer organizations base their assessment on it. The requirement is considered to be met as soon as a sun protection product reduces the in vitro measured transmission in the sector 320 to 360 nanometer by at least 90 percent.

As above 90 percent absorption no further differentiation is to be expected, products with relatively low LPF towards UVB - provided adherence to the Australian standard - still show an adequate UVA protection. In contrast, the UVA protection at products with higher LPF may stagnate at consistent level without infringing the standard. The UVA protection thus does not necessarily increase in relation with the UVB protection. With increasing LPF of the sun protection product hence a steadily increasing UVA dose may impact on skin without noticing by the product user.

Determination of
UVA balance

In order to solve this problem, numerous national and international working groups are involved in establishing of standardized measuring methods for the characterization of UVA-protection. Since February 2005 a new Deutsche Industrienorm (German Industry Standard) (DIN 67502) [16] has been set up. The particular feature of this method is that here first of all the UVA and UVB protection of the product is determined in-vitro and following the resulting measuring value is related to the in vivo determined UVB light protection factor. The UVA protection performance thus ascertained is indicated as UVA balance value.

The method for the determination of the UVA balance is simple and swift in application. Several of the routine screenings performed within the last years have shown that by their application - at only minor variations of the individual values - distinctions in the UVA-protection of sun protection products can be reproducible proven [17-20]. The UVA balance values of the products tested are between below 10 and above 50 whereas the most distinct differences were detected at products with relatively high light protection factors (LPF 15 to 30) and sunscreens for children (LPF 25 to 40).

Despite the easy application and good reproducibility, the method for the determination of the UVA balance has not yet been internationally recognized and is moreover in some aspects subjet to objection. Thus for example it has been criticized that it leaves unconsidered the duration of the protective effect and uses a biological final point the relevance of which has not been proven for long-term skin damage by UVA radiation. In addition, there is no recommendation on hand to date on how high the level of the UVA balance value of a sun protection product should at least be so that an adequate UVA protection can be attributed to it.

Conclusion

As it is uncontested until today that not only UVB but also UVA radiation may induce skin damage, increasing importance is attached to the UVA protective effect of sunscreens. Producers of sun protection products are therefore called upon to provide their products with an adequate UVA protective performance in relation to the UVB protection. This should however not be effected by an uncritical increase of the filter rate in particular for products recommended for the application at delicate skin which may entail an aggravation of the dermal compatibility of the product.

For the orientation of the consumer and advisory bodies of experts it would be helpful if increased transparency on the level of the UVA protection of sun protection products could possibly be established in near future. The question as to how UVA protection could be optimally tested and declared is still pending. The present practice, according to which a product fulfills the Australian standard, signalizes though the presence of UVA protection, does not allow, however, a conclusion on its level in relation to UVB protection. Hence, methods are required exceeding the Australian Standard and supply more explicit data.

From the methods developed so far for the determination of UVA-protection, no internationally recognized standard has been established due to manifold reasons to date. In order to generate - in the sense of the consumer -more transparency at short term, some experts suggest to implement the method ensured in view of its reproducibility according to DIN 67502 in practice already at the time being and to include the results achieved by employing it in the assessment of sun protection products at least until methods with more relevant final points for the routine application are available [21].

For the implementation of this proposal a criterion for the assessment of the UVA-protection performance by means of the UVA balance value would be established the significance of which has not yet been finally clarified. In spite of the unsatisfactory current situation it therefore seems to be more reasonable to subject the method to a further validation while for example testing to what extent the results achieved by this method correlate with results of other test methods before introducing it in practice. This should however not lead to an unacceptably long delay in direction of an approach to a suited solution.

Moreover, it is to be taken in consideration that it may be asked too much of the consumer if in future besides the LPF towards UVB an additional UVA protective value would be declared - determined by what method ever. It should therefore, if so possible, be clarified in the scope of an international consensus finding process whether on medium-term a practicable method for the testing of UV protection of sunscreens can be initiated offering the possibility of expressing the protective performance towards UVA and UVB radiation in one value.