Solar ultraviolet radiation is recognized as a major cause of non-melanoma skincancer in man. Skin cancer occurs most frequently in the most heavily exposedareas and correlates with degree of outdoor exposure. Describing the relationship ofexposure (dose) to risk (skin cancer) requires the availability of a biological hazardfunction or action spectrum for photocarcinogenesis. This standard proposes theadoption of an action spectrum (weighting function) derived from experimentallaboratory data and modified to estimate the non-melanoma tumor response inhuman skin. The experimental data are sufficient for estimating effectiveness down toabout 250 nm, but experimental data are not sufficient for specifying effectivenessabove 400 nm.