yeah, you could get a serious tan from a mh especially, they have a lot of output in UV-B frequency range. incidentally UVB is also most responsible for skin cancers, but uh... it's your skin.
I heard a horror story about the shields on some gymnasium HPS lights malfunctioning, and like 30 people were treated for sun burn and sun poisoning after getting sick. not fun. But that was probably well over 10k+ watts of lighting