Ultraviolet A radiation: testing and labeling for sunscreen products.

Conceptually, sunscreen products are quite simple. The ultraviolet (UV) filters in these products reduce the "dose" of solar energy to which the skin is exposed. Underlying this empirical notion are many complexities including measures of product efficacy and how to communicate this to consumers. The sun protection factor (SPF) test is and should remain the singular in vivo method for evaluating sunscreens. Additionally, substrate spectrophotometric measure of absorbance/transmittance and the calculation of the summary statistic, such as the critical wavelength (ie, lambda(c)), should be used as a means of evaluating broad-spectrum (ie, UVA) protection. Ideally, the photoprotective efficacy of sunscreen products will be communicated to consumers as an SPF no greater than 50 and a single designation of "broad-spectrum" to indicate long-wavelength UVA protection.