Collaborative development of a sun protection factor test method: a proposed European Standard. COLIPA Task Force 'Sun Protection Measurement', Europe.

Synopsis Standardization of the method to determine sun protection factors (SPF) is fundamental to uniform labelling of SPF values on sun products. The COLIPA Task Force 'Sun Protection Measurement'(SPM), including representatives of major European sun-product manufacturers and contract testing laboratories, was established in 1990 to define methods for sun products testing. The process involved in developing the COLlPA SPF Test Method started with a critical appraisal of previously existing methods, and identification of areas for improvement. Experiments were performed by the participating laboratories to establish the new recommended test protocol which was then confirmed in two multicentred ring tests. Improvements to test methodology included the number and selection of volunteers and skin types, the application of the product, the definition of W output from solar simulators, and the method for assessing erythemal response (MED) including an option to use colorimetry to define objectively the 'erythemal threshold' of skin and to predetermine MED prior to exposure. Four cosmetic formulations and neutral density physical filters (SPF from 4 to 20) were tested in two ring tests. Results showed that variations in SPF of the cosmetic products were, on average, directly proportional to SPF value. An excellent correlation was found between visual and colorimetric SPF assessments (r = 0.99). An acceptable range of values for low and high SPF standard products was also established. The COLIPA SPF test method is now fully defined and supported by experimental data. Its use will harmonize SPF testing throughout Europe and help in the quest for global harmonization in testing sun products.

Consequences for sun protection factors when solar simulator spectra deviate from the spectrum of the sun.

Synopsis The sun protection factor (SPF) of two products, one with an expected SPF of 4 and another with an expected SPF of 15 were determined, using two solar simulators: Multiport Solar UV Simulator (xenon, Solar Light, Philadelphia, PA, USA), and Supersun 5000 (metal halide, Mutzhas, Munich, Germany). The mean SPFs using the Multiport were: 4.8 for the low SPF product and 19.4 for the high SPF one. The results using the Supersun were lower: 2.6 for the low SPF product and 7.2 for the high SPF one. Relative emission spectra of the two sources were recorded using a fluorescence spectrophotometer in bioluminescence mode. Efficacy spectra were calculated and compared with the corresponding spectrum of natural sunlight. It was evident that the spectral power of the xenon source is too high in the UVB, leading to overestimation of SPFs, whereas the Supersun irradiator emits too much in the UVA, resulting in too low SPFs. Heat effects and photodegradation of UV filters are discussed as further possible reasons for the discrepancies between the experimentally determined SPFs. Our results confirm a recent publication about theoretical SPFs, calculated with emission spectra of a xenon source and spectra of the sun at different elevation angles, where the authors provide evidence that in natural sunlight the contribution of UVA to total UV radiation is twice as high as in a xenon source. This may contribute to an understanding of why sunscreens tested according to the FDA method (xenon sources) often yield higher SPFs than those obtained from European testing procedures.