i know a guy that says hes gotten sunburned from wearing a long sleeved shirt.... thats why he wears his leather jacket when he welds now....
it jsut usually is a safer practice to always have more than enough safety equipment on... like i said, ive welded several tiems with jsut a tank top on, and never gotten sunburned at all, but then again, im one of thsoe people that doesnt get sunburned either... i jsut tan