Solar radiation in the UVB spectrum (290 nm-320 nm) has been recognized as the primary cause of nonmelanoma skin cancer. Cyclobutane pyrimidine dimers (CPDs) develop in skin exposed to UVB and produce genetic alterations in DNA that cause cutaneous squamous cell and basal cell cancer. Like UVB, UVA can cause nonmelanoma skin cancers, but the tumors take longer to develop and require much larger doses of light due to indirect damage to DNA. At least that?s the conventional wisdom.
In a laboratory study, whole skin was exposed to either UVB or UVA radiation. As expected, the predominant form of DNA damage in the UVB-irradiated skin was the CPD.
Surprisingly, numerous CPDs were found in the UVA samples as well. Compared to UVB-induced CPDs, the UVA-induced CPDs persisted longer in the skin, suggesting that the DNA-repair processes were less effective in removing UVA-induced CPDs than UVB-induced lesions.
If confirmed, these findings make it even more important to be protected from UVA on the beach and reconsider using that tanning lamp.
John Russo, Jr., PharmD, is president of The MedCom Resource, Inc. Previously, he was senior vice president of medical communications at www.Vicus.com, a complementary and alternative medicine website.