IARC Classifies Welding Fumes and UV Radiation as Group 1 Carcinogens“Substantial new evidence” lead to the changeApr 25, 2017The International Agency for Research on Cancer (IARC) has classified welding fumes and UV radiation from welding as Group 1 carcinogens, according to a report.Welding fumes were previously classified in Group 2B, but new evidence from research motivated the change. Two related chemicals, molybdenum trioxide and indium tin oxide, were classified in Group 2B as possibly carcinogenic to humans based on “sufficient evidence.” The group will meet again in June to review chemicals in food and consumer products.