research indicates that exposure to the UV-B ionizing radiation in sunlight is the primary cause of squamous cell (Figure 19-E, left) and basal cell (Figure 19-E, center) skin cancers. Together, these two types account for 95% of all skin cancers. Typically, a 15- to 40-year lag separates excessive exposure to UV-B and the development of these cancers. Caucasian children and adolescents who experience only a single severe sunburn