even though spray tanning is a kind of sunless tanning or has no UV ray side effects ..it can be a bad idea to use spray tan according to Dr.Monica Gaughan which was published in online news of Grady College of Journalism at the University of Georgia.
He told so as - FDA do not approved external use os spray tan yet. this means breathing or taking spray for internal use prohobited. Tanning spray might damage ones DNA.
we need to use sunless tanning to stop being exposed with UV. but spray tan should be avoided for possible side effects, you can use idol tan as alternative.
Note that study was not conducted upon human but was conducted upon mice and cells.Source http://gradynewsource.uga.edu/tele5560/spray-tan-dangers/