Ultraviolet A transmission by modern sunscreens: is there a real risk?

In recent years it has been realized that ultraviolet A (UVA) is capable of inducing many of the same deleterious events as UVB. In addition to erythema, UVA can cause connective tissue damage and is photocarcinogenic. Recently, concern has arisen that new, higher potency sunscreens allow dangerous amount of UVA to reach the skin, because they allow prolonged outdoor exposure. Such concerns are unfounded. The problem lies in a misunderstanding of the concept of sunlight protection factor. This is purely a multiplication factor and does not indicate that the effect of transmitted UVR is due to UVA or UVB. Action spectra show that UVA is less, but certainly not more injurious to skin than UVB. There is no reason to believe that higher potency sunscreens enhance exposure to dangerous amounts of UVA.