Solar intensity and sun protection

To the Editor.— Weinstock et al1 observed "a significant association of melanoma with latitude of residence during the teenage years," thereby implying a direct relationship between solar radiation intensity and increasing tropical latitude. However, for specific locations, this relationship may not be true. For example, average daily solar radiation in Spokane, WA (latitude 47 degrees, 40 minutes, elevation 2400 feet), was 1314 BTU during July, compared to 862 BTU in Charleston, SC (latitude 32 degrees, 53 minutes, elevation sea level).2