Epidemiological evidence that UVA radiation is involved in the genesis of cutaneous melanoma

Epidemiological data have contributed to the classification in 2009 of the full ultraviolet (UV) radiation spectrum as carcinogenic to humans. We reviewed the epidemiological evidence that UVA could be involved in the genesis of cutaneous melanoma.

Use of artificial UV tanning devices (sunbeds) consists mainly of repeated exposure to high UVA doses. Epidemiological studies published over the last years confirmed the association between sunbed use and melanoma. Sunbed use is the most probable cause of an epidemic of melanoma that took place in Iceland from 1990 to 2006. The four-fold increase in melanoma incidence was not followed by an increase in melanoma mortality. Sunscreens were primarily devised for the prevention of sunburn, and UVB is the wavelength causing most sunburns. All observational studies and randomized trials show that sunscreen use may extend sun exposure intended for getting a tan, while it does not necessarily decrease sunburn occurrence. Sunscreen use for tan acquisition would thus lead to similar exposure to UVB and greater exposure to UVA, which could explain the slightly higher melanoma risk often found among sunscreen users.

UVA could be involved in the occurrence of nonlife-threatening melanoma. The increasing use of sunbeds and of sunscreens may partly explain why melanoma incidence increases in most light-skinned populations without concomitant increase in mortality.