Arc welding emits UV and IR radiation, all part of the electromagnetic spectrum (EMR), just different frequencies. (Had to learn this for RT.)
The order of these from decreasing to increasing wavelengths are:
X and Gamma rays
UV
visible light
IR (heat)
Radar
short wave radio
long wave radio
Have you ever seen what a cell phone repeater can due to the side of a building with EMR? It will burn the substrate due to the intesity.
All can be hazardous, depends on intensity.
Hey, all that training was good for something!