Can UV radiation be safe for the skin?
You're talking about long-wave UV, or UV-A radiation. In the 80s, experts claimed that this was a safe wavelength. Protection against UV-A was not part of sunscreen in the early days. Consequently, UV-A was (and still is) used in tanning beds due to its perceived safety over UV-B. However, a lot of research has been done since.

UV-A is well understood now to also be unsafe in unreasonable amounts. Currently, UV-A protection is a typical feature of sunscreen and tanning beds are still not a healthy alternative to moderate, healthy doses of sun. Here is a recent review covering some of the aspects comparing different UV range effects on skin. I really suggest you put a search engine to good use here; it makes little sense for us to expound on the literature when it is so clear and easily available.

In summary,


UVA certainly contributes to the development of skin cancer.
UVA penetrates deeper into the skin than UV-B (which is largely responsible for 'burning' of the topmost layer of skin, without directly affecting the deeper layers). For this reason, UV-B is associated primarily with burning and UV-A is primarily associated with aging and aging diseases like cancer.
It is important to note that 95% of UV light in every day life is UV-A, because it does not vary seasonally and can penetrate clouds and windows. Therefore, in spite of the fact that short wavelengths carry more energy per photon, the ratios of UV-A and UV-B exposure are far from equal.


These are only a few of the explanations as to why we observe an incidence of aging and skin damage and disease upon UV-A exposure.