A recent study from The University of Texas MD Anderson Cancer Center has reversed previous findings that early life exposure to ultraviolet A (UVA) light causes melanoma. According to the findings, UVA exposure is unlikely to have contributed to the rise in occurrences of melanoma over the past 30 years because the fish model is the only animal model to show a connection between UVA exposure at a young age and melanoma development.
While the study disproves a link between UVA exposure and melanoma, it does not mean that UVA rays are completely harmless. UVA is a carcinogen and can cause premature aging of the skin as well as suppress the immune system. The authors also note that it is possible that chronic exposure to UVA can speed up the progression of cells that are already pre-cancerous.
The study tested the effects of UVA and ultraviolet B (UVB) lights on melanoma-prone fish during the first few days of their life. While the fish exposed to the UVB light had a 43% incidence of melanoma, the control group (no UVA/B exposure) had an 18.4% incidence and the fish exposed to UVA only had a 12.4% incidence.
A controversial study in 1993 had linked UVA exposure to melanoma. Prior to that study, sunscreens only protected against UVB exposure—this became a huge public health concern considering UVA makes up 90% of the ultraviolet spectrum. Following the 1993 study, most researchers believed the high rate of melanoma to be linked to early UVA exposure prior to changes made to sunscreen.
The 1993 study results could not be duplicated in the mammalian model and in hindsight there were numerous problems with the research and sample sizes. The scientists at The University of Texas tried to recreate the mammalian model with a larger sample size in order to obtain stronger conclusions.
The recreated mammalian study found that UVB exposures damages DNA directly, while UVA may induce melanin free radicals that react with DNA to form oxidative damage that will indirectly lead to melanoma. No direct correlation between UVA and melanoma was made.
Further research is still needed to understand if there is an indirect correlation between melanoma and UVA. Future studies may prove that UVA and UVB work symbiotically to cause melanoma. That being said, I still stress the same advice about sun exposure: keep it to a minimum and always wear sunscreen!