Some researchers feel that it’s best to focus on UVB and get much smaller UVA. This would be consistent with getting vitamin d and avoiding some of the skin cancer risks. However, many people that regularly come out in the sun getting “farmer’s tan” appear to be healthy towards bad skin cancers. UVA in small doses over a prolonged period (and especially in body parts that normally would get sun anyway and likely have extra evolutionary protections) seems to neutralize the skin cancer risks. I’m not sure, but do consider looking into short term tanning with a UVB-focused lamp that matches the sun’s output of UVB as an alternative to “full spectrum”.