Although anti-tanning advocates are fond of claiming that ultraviolet radiation “causes” melanoma, such a statement grossly misrepresents what is known about human exposure to ultraviolet radiation and melanoma.
First, we know that the vasty majority of people exposed to ultraviolet radiation (regardless of source) — including the vast majority of those who are overexposed to the point of severe sunburn — do not develop melanoma. So we know that mere exposure, and even overexposure, to ultraviolet radiation do not by themselves cause melanoma to develop.
The best science can do so far is to identify risk factors for melanoma.
Skin color. For example, whites are at much greater risk of melanoma as compared with blacks, and fair-skinned whites are at much greater risk of melanoma than whites who tan more easily.
Personal history. People who have had melanoma are at greater risk of developing melanoma.
Family history. If people in your family have had melanoma, you may be a greater risk of melanoma as well.
Skin lesions. Chronic skin lesions called nevi, like birthmarks, increase the risk of melanoma.
Age. As shown in the chart below, the older you are, the higher your risk of melanoma.
Although some call UV a “cause” of cancer, it is, at best a risk factor — like those listed above.
An April 2013 study published in the American Journal of Epidemiology reported the following risk factors for malignant melanoma in situ (MMIS):
Meta-analysis across the cohorts demonstrated that the presence of multiple nevi on the extremities conferred the highest relative risk for MMIS (relative risk = 3.18, 95% confidence interval: 2.59, 3.90). Family history of melanoma, number of severe sunburns, sunburn susceptibility, hair color, and Fitzpatrick skin types I, II, and III were significantly associated with an increased risk of MMIS.
The study went on to report that UV radiation was not associated with MMIS:
Conversely, the ultraviolet index of the state of residence at birth, at age 15 years, and at age 30 years was not associated with increased risk of MMIS. Continued study of MMIS and associated risk factors will help identify persons who are most at risk and elucidate the role of MMIS within the spectrum of cutaneous melanoma.
There is one big difference between UV radiation and the other risk factors for melanoma. With the other risk factors, the more you have of them, the greater your risk for melanoma — i.e, the older you are, the more nevi you have, the fairer your skin etc. These “dose-response” relationships have not been established by scientists for UV radiation and melanoma.
There is no question that UV radiation has biological effects on the skin. But the precise nature of the relationship between UV radiation and melanoma and other skin cancers has yet to be discerned.
In the end, melanoma is rare and death from melanoma rare still — despite much UV exposure. While other skin cancers have higher incidence rates than melanoma, they are rarely fatal.