New methods for assessing secondary performance attributes of sunscreens suitable for professional outdoor work

Outdoor workers (OW) are highly exposed to solar ultraviolet radiation (UVR) and thus at increased risk for developing skin cancer. An essential part of an overall strategy to reduce workplace UVR-exposure to OW's skin is the usage of sunscreens. However, compliance with regular sunscreen usage seems to be low, as products are usually designed for recreational sun exposure and thus do not meet the requirements of physically active OW. To date, no standardized test procedures assess the suitability of sunscreens for professional use. The aim of this pilot study was to develop standardized methods of testing secondary performance attributes (PA) to represent real-life working conditions of outdoor work.

Ten sunscreen products, carefully selected after a detailed market survey of all relevant producers available on the German market, were evaluated regarding their suitability for professional outdoor work on 24 healthy volunteers in a newly designed test procedure. In addition to three standardized efficacy characteristics, i.e., sun protection factor, water-resistance, and UVA protection, we evaluated each PA involving parameters typically associated with outdoor workplaces.

We developed standardized methods for objectifying the suitability of sunscreen products for professional outdoor work. The test procedures used are well feasible and appropriate for testing the PA because they represent practical working conditions in detail - although the degree of discriminability of single test methods varied. The claimed sun protection factor (SPF) of the products was confirmed; bio-stability of the SPF after physical activity was achieved in most cases. While most products hardly irritate the eyes and are quickly absorbed, the evaluation of the subjective skin feeling and non-slip grip is inconsistent.

In this pilot study, for the first time secondary PA are defined and examined. Although further objectification of the PA assessment as well as the establishment of minimum standards should be sought, the new methods could already complement the so far mandatory labels and in this way provide a significant impetus for the current scientific and political focus on the improvement of occupational health in highly UVR-exposed OW.