Solar ultraviolet irradiance and cancer incidence and mortality

Abstract

Rates for many cancers are generally higher with increased distance from the equator. The first paper positing a link between sunlight and reduced risk of cancer was published in 1937.1 Persons in the US Navy with greater "skin irritation" (actinic keratosis and skin cancer) had lower risk of internal cancers. A second paper appeared then reported that residents of sunnier states had lower cancer risk.1 Although many studies have tried to explain these geographic variations, including differences in dietary factors and socioeconomic status, the most promising is that solar ultraviolet-B (UVB) (290-315 nm), through production of vitamin D, reduces the risk of cancer incidence and increases survival chances. Data at the World Health Organization3 indicated large latitudinal gradients in cancer mortality rates recorded as early as 1955 for breast, colon, intestinal, lung, prostate, rectal and renal cancer. However, rates were also low for countries where much fish was consumed, such as Iceland and Japan and in countries where animal products were a small fraction of the total energy supply, such as Egypt. Thus, it would have taken a clever researcher to suggest that solar UVB and fish were important sources of vitamin D and could explain much of the variance. © 2008 Springer New York.